readwrite.c 55.8 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299
/*
 * fs/logfs/readwrite.c
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
 *
 *
 * Actually contains five sets of very similar functions:
 * read		read blocks from a file
 * seek_hole	find next hole
 * seek_data	find next data block
 * valid	check whether a block still belongs to a file
 * write	write blocks to a file
 * delete	delete a block (for directories and ifile)
 * rewrite	move existing blocks of a file to a new location (gc helper)
 * truncate	truncate a file
 */
#include "logfs.h"
#include <linux/sched.h>
#include <linux/slab.h>

static u64 adjust_bix(u64 bix, level_t level)
{
	switch (level) {
	case 0:
		return bix;
	case LEVEL(1):
		return max_t(u64, bix, I0_BLOCKS);
	case LEVEL(2):
		return max_t(u64, bix, I1_BLOCKS);
	case LEVEL(3):
		return max_t(u64, bix, I2_BLOCKS);
	case LEVEL(4):
		return max_t(u64, bix, I3_BLOCKS);
	case LEVEL(5):
		return max_t(u64, bix, I4_BLOCKS);
	default:
		WARN_ON(1);
		return bix;
	}
}

static inline u64 maxbix(u8 height)
{
	return 1ULL << (LOGFS_BLOCK_BITS * height);
}

/**
 * The inode address space is cut in two halves.  Lower half belongs to data
 * pages, upper half to indirect blocks.  If the high bit (INDIRECT_BIT) is
 * set, the actual block index (bix) and level can be derived from the page
 * index.
 *
 * The lowest three bits of the block index are set to 0 after packing and
 * unpacking.  Since the lowest n bits (9 for 4KiB blocksize) are ignored
 * anyway this is harmless.
 */
#define ARCH_SHIFT	(BITS_PER_LONG - 32)
#define INDIRECT_BIT	(0x80000000UL << ARCH_SHIFT)
#define LEVEL_SHIFT	(28 + ARCH_SHIFT)
static inline pgoff_t first_indirect_block(void)
{
	return INDIRECT_BIT | (1ULL << LEVEL_SHIFT);
}

pgoff_t logfs_pack_index(u64 bix, level_t level)
{
	pgoff_t index;

	BUG_ON(bix >= INDIRECT_BIT);
	if (level == 0)
		return bix;

	index  = INDIRECT_BIT;
	index |= (__force long)level << LEVEL_SHIFT;
	index |= bix >> ((__force u8)level * LOGFS_BLOCK_BITS);
	return index;
}

void logfs_unpack_index(pgoff_t index, u64 *bix, level_t *level)
{
	u8 __level;

	if (!(index & INDIRECT_BIT)) {
		*bix = index;
		*level = 0;
		return;
	}

	__level = (index & ~INDIRECT_BIT) >> LEVEL_SHIFT;
	*level = LEVEL(__level);
	*bix = (index << (__level * LOGFS_BLOCK_BITS)) & ~INDIRECT_BIT;
	*bix = adjust_bix(*bix, *level);
	return;
}
#undef ARCH_SHIFT
#undef INDIRECT_BIT
#undef LEVEL_SHIFT

/*
 * Time is stored as nanoseconds since the epoch.
 */
static struct timespec be64_to_timespec(__be64 betime)
{
	return ns_to_timespec(be64_to_cpu(betime));
}

static __be64 timespec_to_be64(struct timespec tsp)
{
	return cpu_to_be64((u64)tsp.tv_sec * NSEC_PER_SEC + tsp.tv_nsec);
}

static void logfs_disk_to_inode(struct logfs_disk_inode *di, struct inode*inode)
{
	struct logfs_inode *li = logfs_inode(inode);
	int i;

	inode->i_mode	= be16_to_cpu(di->di_mode);
	li->li_height	= di->di_height;
	li->li_flags	= be32_to_cpu(di->di_flags);
	i_uid_write(inode, be32_to_cpu(di->di_uid));
	i_gid_write(inode, be32_to_cpu(di->di_gid));
	inode->i_size	= be64_to_cpu(di->di_size);
	logfs_set_blocks(inode, be64_to_cpu(di->di_used_bytes));
	inode->i_atime	= be64_to_timespec(di->di_atime);
	inode->i_ctime	= be64_to_timespec(di->di_ctime);
	inode->i_mtime	= be64_to_timespec(di->di_mtime);
	set_nlink(inode, be32_to_cpu(di->di_refcount));
	inode->i_generation = be32_to_cpu(di->di_generation);

	switch (inode->i_mode & S_IFMT) {
	case S_IFSOCK:	/* fall through */
	case S_IFBLK:	/* fall through */
	case S_IFCHR:	/* fall through */
	case S_IFIFO:
		inode->i_rdev = be64_to_cpu(di->di_data[0]);
		break;
	case S_IFDIR:	/* fall through */
	case S_IFREG:	/* fall through */
	case S_IFLNK:
		for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
			li->li_data[i] = be64_to_cpu(di->di_data[i]);
		break;
	default:
		BUG();
	}
}

static void logfs_inode_to_disk(struct inode *inode, struct logfs_disk_inode*di)
{
	struct logfs_inode *li = logfs_inode(inode);
	int i;

	di->di_mode	= cpu_to_be16(inode->i_mode);
	di->di_height	= li->li_height;
	di->di_pad	= 0;
	di->di_flags	= cpu_to_be32(li->li_flags);
	di->di_uid	= cpu_to_be32(i_uid_read(inode));
	di->di_gid	= cpu_to_be32(i_gid_read(inode));
	di->di_size	= cpu_to_be64(i_size_read(inode));
	di->di_used_bytes = cpu_to_be64(li->li_used_bytes);
	di->di_atime	= timespec_to_be64(inode->i_atime);
	di->di_ctime	= timespec_to_be64(inode->i_ctime);
	di->di_mtime	= timespec_to_be64(inode->i_mtime);
	di->di_refcount	= cpu_to_be32(inode->i_nlink);
	di->di_generation = cpu_to_be32(inode->i_generation);

	switch (inode->i_mode & S_IFMT) {
	case S_IFSOCK:	/* fall through */
	case S_IFBLK:	/* fall through */
	case S_IFCHR:	/* fall through */
	case S_IFIFO:
		di->di_data[0] = cpu_to_be64(inode->i_rdev);
		break;
	case S_IFDIR:	/* fall through */
	case S_IFREG:	/* fall through */
	case S_IFLNK:
		for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
			di->di_data[i] = cpu_to_be64(li->li_data[i]);
		break;
	default:
		BUG();
	}
}

static void __logfs_set_blocks(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_inode *li = logfs_inode(inode);

	inode->i_blocks = ULONG_MAX;
	if (li->li_used_bytes >> sb->s_blocksize_bits < ULONG_MAX)
		inode->i_blocks = ALIGN(li->li_used_bytes, 512) >> 9;
}

void logfs_set_blocks(struct inode *inode, u64 bytes)
{
	struct logfs_inode *li = logfs_inode(inode);

	li->li_used_bytes = bytes;
	__logfs_set_blocks(inode);
}

static void prelock_page(struct super_block *sb, struct page *page, int lock)
{
	struct logfs_super *super = logfs_super(sb);

	BUG_ON(!PageLocked(page));
	if (lock) {
		BUG_ON(PagePreLocked(page));
		SetPagePreLocked(page);
	} else {
		/* We are in GC path. */
		if (PagePreLocked(page))
			super->s_lock_count++;
		else
			SetPagePreLocked(page);
	}
}

static void preunlock_page(struct super_block *sb, struct page *page, int lock)
{
	struct logfs_super *super = logfs_super(sb);

	BUG_ON(!PageLocked(page));
	if (lock)
		ClearPagePreLocked(page);
	else {
		/* We are in GC path. */
		BUG_ON(!PagePreLocked(page));
		if (super->s_lock_count)
			super->s_lock_count--;
		else
			ClearPagePreLocked(page);
	}
}

/*
 * Logfs is prone to an AB-BA deadlock where one task tries to acquire
 * s_write_mutex with a locked page and GC tries to get that page while holding
 * s_write_mutex.
 * To solve this issue logfs will ignore the page lock iff the page in question
 * is waiting for s_write_mutex.  We annotate this fact by setting PG_pre_locked
 * in addition to PG_locked.
 */
void logfs_get_wblocks(struct super_block *sb, struct page *page, int lock)
{
	struct logfs_super *super = logfs_super(sb);

	if (page)
		prelock_page(sb, page, lock);

	if (lock) {
		mutex_lock(&super->s_write_mutex);
		logfs_gc_pass(sb);
		/* FIXME: We also have to check for shadowed space
		 * and mempool fill grade */
	}
}

void logfs_put_wblocks(struct super_block *sb, struct page *page, int lock)
{
	struct logfs_super *super = logfs_super(sb);

	if (page)
		preunlock_page(sb, page, lock);
	/* Order matters - we must clear PG_pre_locked before releasing
	 * s_write_mutex or we could race against another task. */
	if (lock)
		mutex_unlock(&super->s_write_mutex);
}

static struct page *logfs_get_read_page(struct inode *inode, u64 bix,
		level_t level)
{
	return find_or_create_page(inode->i_mapping,
			logfs_pack_index(bix, level), GFP_NOFS);
}

static void logfs_put_read_page(struct page *page)
{
	unlock_page(page);
	page_cache_release(page);
}

static void logfs_lock_write_page(struct page *page)
{
	int loop = 0;

	while (unlikely(!trylock_page(page))) {
		if (loop++ > 0x1000) {
			/* Has been observed once so far... */
			printk(KERN_ERR "stack at %p\n", &loop);
			BUG();
		}
		if (PagePreLocked(page)) {
			/* Holder of page lock is waiting for us, it
			 * is safe to use this page. */
			break;
		}
		/* Some other process has this page locked and has
		 * nothing to do with us.  Wait for it to finish.
		 */
		schedule();
	}
	BUG_ON(!PageLocked(page));
}

static struct page *logfs_get_write_page(struct inode *inode, u64 bix,
		level_t level)
{
	struct address_space *mapping = inode->i_mapping;
	pgoff_t index = logfs_pack_index(bix, level);
	struct page *page;
	int err;

repeat:
	page = find_get_page(mapping, index);
	if (!page) {
		page = __page_cache_alloc(GFP_NOFS);
		if (!page)
			return NULL;
		err = add_to_page_cache_lru(page, mapping, index, GFP_NOFS);
		if (unlikely(err)) {
			page_cache_release(page);
			if (err == -EEXIST)
				goto repeat;
			return NULL;
		}
	} else logfs_lock_write_page(page);
	BUG_ON(!PageLocked(page));
	return page;
}

static void logfs_unlock_write_page(struct page *page)
{
	if (!PagePreLocked(page))
		unlock_page(page);
}

static void logfs_put_write_page(struct page *page)
{
	logfs_unlock_write_page(page);
	page_cache_release(page);
}

static struct page *logfs_get_page(struct inode *inode, u64 bix, level_t level,
		int rw)
{
	if (rw == READ)
		return logfs_get_read_page(inode, bix, level);
	else
		return logfs_get_write_page(inode, bix, level);
}

static void logfs_put_page(struct page *page, int rw)
{
	if (rw == READ)
		logfs_put_read_page(page);
	else
		logfs_put_write_page(page);
}

static unsigned long __get_bits(u64 val, int skip, int no)
{
	u64 ret = val;

	ret >>= skip * no;
	ret <<= 64 - no;
	ret >>= 64 - no;
	return ret;
}

static unsigned long get_bits(u64 val, level_t skip)
{
	return __get_bits(val, (__force int)skip, LOGFS_BLOCK_BITS);
}

static inline void init_shadow_tree(struct super_block *sb,
		struct shadow_tree *tree)
{
	struct logfs_super *super = logfs_super(sb);

	btree_init_mempool64(&tree->new, super->s_btree_pool);
	btree_init_mempool64(&tree->old, super->s_btree_pool);
}

static void indirect_write_block(struct logfs_block *block)
{
	struct page *page;
	struct inode *inode;
	int ret;

	page = block->page;
	inode = page->mapping->host;
	logfs_lock_write_page(page);
	ret = logfs_write_buf(inode, page, 0);
	logfs_unlock_write_page(page);
	/*
	 * This needs some rework.  Unless you want your filesystem to run
	 * completely synchronously (you don't), the filesystem will always
	 * report writes as 'successful' before the actual work has been
	 * done.  The actual work gets done here and this is where any errors
	 * will show up.  And there isn't much we can do about it, really.
	 *
	 * Some attempts to fix the errors (move from bad blocks, retry io,...)
	 * have already been done, so anything left should be either a broken
	 * device or a bug somewhere in logfs itself.  Being relatively new,
	 * the odds currently favor a bug, so for now the line below isn't
	 * entirely tasteles.
	 */
	BUG_ON(ret);
}

static void inode_write_block(struct logfs_block *block)
{
	struct inode *inode;
	int ret;

	inode = block->inode;
	if (inode->i_ino == LOGFS_INO_MASTER)
		logfs_write_anchor(inode->i_sb);
	else {
		ret = __logfs_write_inode(inode, NULL, 0);
		/* see indirect_write_block comment */
		BUG_ON(ret);
	}
}

/*
 * This silences a false, yet annoying gcc warning.  I hate it when my editor
 * jumps into bitops.h each time I recompile this file.
 * TODO: Complain to gcc folks about this and upgrade compiler.
 */
static unsigned long fnb(const unsigned long *addr,
		unsigned long size, unsigned long offset)
{
	return find_next_bit(addr, size, offset);
}

static __be64 inode_val0(struct inode *inode)
{
	struct logfs_inode *li = logfs_inode(inode);
	u64 val;

	/*
	 * Explicit shifting generates good code, but must match the format
	 * of the structure.  Add some paranoia just in case.
	 */
	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_mode) != 0);
	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_height) != 2);
	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_flags) != 4);

	val =	(u64)inode->i_mode << 48 |
		(u64)li->li_height << 40 |
		(u64)li->li_flags;
	return cpu_to_be64(val);
}

static int inode_write_alias(struct super_block *sb,
		struct logfs_block *block, write_alias_t *write_one_alias)
{
	struct inode *inode = block->inode;
	struct logfs_inode *li = logfs_inode(inode);
	unsigned long pos;
	u64 ino , bix;
	__be64 val;
	level_t level;
	int err;

	for (pos = 0; ; pos++) {
		pos = fnb(block->alias_map, LOGFS_BLOCK_FACTOR, pos);
		if (pos >= LOGFS_EMBEDDED_FIELDS + INODE_POINTER_OFS)
			return 0;

		switch (pos) {
		case INODE_HEIGHT_OFS:
			val = inode_val0(inode);
			break;
		case INODE_USED_OFS:
			val = cpu_to_be64(li->li_used_bytes);
			break;
		case INODE_SIZE_OFS:
			val = cpu_to_be64(i_size_read(inode));
			break;
		case INODE_POINTER_OFS ... INODE_POINTER_OFS + LOGFS_EMBEDDED_FIELDS - 1:
			val = cpu_to_be64(li->li_data[pos - INODE_POINTER_OFS]);
			break;
		default:
			BUG();
		}

		ino = LOGFS_INO_MASTER;
		bix = inode->i_ino;
		level = LEVEL(0);
		err = write_one_alias(sb, ino, bix, level, pos, val);
		if (err)
			return err;
	}
}

static int indirect_write_alias(struct super_block *sb,
		struct logfs_block *block, write_alias_t *write_one_alias)
{
	unsigned long pos;
	struct page *page = block->page;
	u64 ino , bix;
	__be64 *child, val;
	level_t level;
	int err;

	for (pos = 0; ; pos++) {
		pos = fnb(block->alias_map, LOGFS_BLOCK_FACTOR, pos);
		if (pos >= LOGFS_BLOCK_FACTOR)
			return 0;

		ino = page->mapping->host->i_ino;
		logfs_unpack_index(page->index, &bix, &level);
		child = kmap_atomic(page);
		val = child[pos];
		kunmap_atomic(child);
		err = write_one_alias(sb, ino, bix, level, pos, val);
		if (err)
			return err;
	}
}

int logfs_write_obj_aliases_pagecache(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_block *block;
	int err;

	list_for_each_entry(block, &super->s_object_alias, alias_list) {
		err = block->ops->write_alias(sb, block, write_alias_journal);
		if (err)
			return err;
	}
	return 0;
}

void __free_block(struct super_block *sb, struct logfs_block *block)
{
	BUG_ON(!list_empty(&block->item_list));
	list_del(&block->alias_list);
	mempool_free(block, logfs_super(sb)->s_block_pool);
}

static void inode_free_block(struct super_block *sb, struct logfs_block *block)
{
	struct inode *inode = block->inode;

	logfs_inode(inode)->li_block = NULL;
	__free_block(sb, block);
}

static void indirect_free_block(struct super_block *sb,
		struct logfs_block *block)
{
	struct page *page = block->page;

	if (PagePrivate(page)) {
		ClearPagePrivate(page);
		page_cache_release(page);
		set_page_private(page, 0);
	}
	__free_block(sb, block);
}


static struct logfs_block_ops inode_block_ops = {
	.write_block = inode_write_block,
	.free_block = inode_free_block,
	.write_alias = inode_write_alias,
};

struct logfs_block_ops indirect_block_ops = {
	.write_block = indirect_write_block,
	.free_block = indirect_free_block,
	.write_alias = indirect_write_alias,
};

struct logfs_block *__alloc_block(struct super_block *sb,
		u64 ino, u64 bix, level_t level)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_block *block;

	block = mempool_alloc(super->s_block_pool, GFP_NOFS);
	memset(block, 0, sizeof(*block));
	INIT_LIST_HEAD(&block->alias_list);
	INIT_LIST_HEAD(&block->item_list);
	block->sb = sb;
	block->ino = ino;
	block->bix = bix;
	block->level = level;
	return block;
}

static void alloc_inode_block(struct inode *inode)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct logfs_block *block;

	if (li->li_block)
		return;

	block = __alloc_block(inode->i_sb, LOGFS_INO_MASTER, inode->i_ino, 0);
	block->inode = inode;
	li->li_block = block;
	block->ops = &inode_block_ops;
}

void initialize_block_counters(struct page *page, struct logfs_block *block,
		__be64 *array, int page_is_empty)
{
	u64 ptr;
	int i, start;

	block->partial = 0;
	block->full = 0;
	start = 0;
	if (page->index < first_indirect_block()) {
		/* Counters are pointless on level 0 */
		return;
	}
	if (page->index == first_indirect_block()) {
		/* Skip unused pointers */
		start = I0_BLOCKS;
		block->full = I0_BLOCKS;
	}
	if (!page_is_empty) {
		for (i = start; i < LOGFS_BLOCK_FACTOR; i++) {
			ptr = be64_to_cpu(array[i]);
			if (ptr)
				block->partial++;
			if (ptr & LOGFS_FULLY_POPULATED)
				block->full++;
		}
	}
}

static void alloc_data_block(struct inode *inode, struct page *page)
{
	struct logfs_block *block;
	u64 bix;
	level_t level;

	if (PagePrivate(page))
		return;

	logfs_unpack_index(page->index, &bix, &level);
	block = __alloc_block(inode->i_sb, inode->i_ino, bix, level);
	block->page = page;

	SetPagePrivate(page);
	page_cache_get(page);
	set_page_private(page, (unsigned long) block);

	block->ops = &indirect_block_ops;
}

static void alloc_indirect_block(struct inode *inode, struct page *page,
		int page_is_empty)
{
	struct logfs_block *block;
	__be64 *array;

	if (PagePrivate(page))
		return;

	alloc_data_block(inode, page);

	block = logfs_block(page);
	array = kmap_atomic(page);
	initialize_block_counters(page, block, array, page_is_empty);
	kunmap_atomic(array);
}

static void block_set_pointer(struct page *page, int index, u64 ptr)
{
	struct logfs_block *block = logfs_block(page);
	__be64 *array;
	u64 oldptr;

	BUG_ON(!block);
	array = kmap_atomic(page);
	oldptr = be64_to_cpu(array[index]);
	array[index] = cpu_to_be64(ptr);
	kunmap_atomic(array);
	SetPageUptodate(page);

	block->full += !!(ptr & LOGFS_FULLY_POPULATED)
		- !!(oldptr & LOGFS_FULLY_POPULATED);
	block->partial += !!ptr - !!oldptr;
}

static u64 block_get_pointer(struct page *page, int index)
{
	__be64 *block;
	u64 ptr;

	block = kmap_atomic(page);
	ptr = be64_to_cpu(block[index]);
	kunmap_atomic(block);
	return ptr;
}

static int logfs_read_empty(struct page *page)
{
	zero_user_segment(page, 0, PAGE_CACHE_SIZE);
	return 0;
}

static int logfs_read_direct(struct inode *inode, struct page *page)
{
	struct logfs_inode *li = logfs_inode(inode);
	pgoff_t index = page->index;
	u64 block;

	block = li->li_data[index];
	if (!block)
		return logfs_read_empty(page);

	return logfs_segment_read(inode, page, block, index, 0);
}

static int logfs_read_loop(struct inode *inode, struct page *page,
		int rw_context)
{
	struct logfs_inode *li = logfs_inode(inode);
	u64 bix, bofs = li->li_data[INDIRECT_INDEX];
	level_t level, target_level;
	int ret;
	struct page *ipage;

	logfs_unpack_index(page->index, &bix, &target_level);
	if (!bofs)
		return logfs_read_empty(page);

	if (bix >= maxbix(li->li_height))
		return logfs_read_empty(page);

	for (level = LEVEL(li->li_height);
			(__force u8)level > (__force u8)target_level;
			level = SUBLEVEL(level)){
		ipage = logfs_get_page(inode, bix, level, rw_context);
		if (!ipage)
			return -ENOMEM;

		ret = logfs_segment_read(inode, ipage, bofs, bix, level);
		if (ret) {
			logfs_put_read_page(ipage);
			return ret;
		}

		bofs = block_get_pointer(ipage, get_bits(bix, SUBLEVEL(level)));
		logfs_put_page(ipage, rw_context);
		if (!bofs)
			return logfs_read_empty(page);
	}

	return logfs_segment_read(inode, page, bofs, bix, 0);
}

static int logfs_read_block(struct inode *inode, struct page *page,
		int rw_context)
{
	pgoff_t index = page->index;

	if (index < I0_BLOCKS)
		return logfs_read_direct(inode, page);
	return logfs_read_loop(inode, page, rw_context);
}

static int logfs_exist_loop(struct inode *inode, u64 bix)
{
	struct logfs_inode *li = logfs_inode(inode);
	u64 bofs = li->li_data[INDIRECT_INDEX];
	level_t level;
	int ret;
	struct page *ipage;

	if (!bofs)
		return 0;
	if (bix >= maxbix(li->li_height))
		return 0;

	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)) {
		ipage = logfs_get_read_page(inode, bix, level);
		if (!ipage)
			return -ENOMEM;

		ret = logfs_segment_read(inode, ipage, bofs, bix, level);
		if (ret) {
			logfs_put_read_page(ipage);
			return ret;
		}

		bofs = block_get_pointer(ipage, get_bits(bix, SUBLEVEL(level)));
		logfs_put_read_page(ipage);
		if (!bofs)
			return 0;
	}

	return 1;
}

int logfs_exist_block(struct inode *inode, u64 bix)
{
	struct logfs_inode *li = logfs_inode(inode);

	if (bix < I0_BLOCKS)
		return !!li->li_data[bix];
	return logfs_exist_loop(inode, bix);
}

static u64 seek_holedata_direct(struct inode *inode, u64 bix, int data)
{
	struct logfs_inode *li = logfs_inode(inode);

	for (; bix < I0_BLOCKS; bix++)
		if (data ^ (li->li_data[bix] == 0))
			return bix;
	return I0_BLOCKS;
}

static u64 seek_holedata_loop(struct inode *inode, u64 bix, int data)
{
	struct logfs_inode *li = logfs_inode(inode);
	__be64 *rblock;
	u64 increment, bofs = li->li_data[INDIRECT_INDEX];
	level_t level;
	int ret, slot;
	struct page *page;

	BUG_ON(!bofs);

	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)) {
		increment = 1 << (LOGFS_BLOCK_BITS * ((__force u8)level-1));
		page = logfs_get_read_page(inode, bix, level);
		if (!page)
			return bix;

		ret = logfs_segment_read(inode, page, bofs, bix, level);
		if (ret) {
			logfs_put_read_page(page);
			return bix;
		}

		slot = get_bits(bix, SUBLEVEL(level));
		rblock = kmap_atomic(page);
		while (slot < LOGFS_BLOCK_FACTOR) {
			if (data && (rblock[slot] != 0))
				break;
			if (!data && !(be64_to_cpu(rblock[slot]) & LOGFS_FULLY_POPULATED))
				break;
			slot++;
			bix += increment;
			bix &= ~(increment - 1);
		}
		if (slot >= LOGFS_BLOCK_FACTOR) {
			kunmap_atomic(rblock);
			logfs_put_read_page(page);
			return bix;
		}
		bofs = be64_to_cpu(rblock[slot]);
		kunmap_atomic(rblock);
		logfs_put_read_page(page);
		if (!bofs) {
			BUG_ON(data);
			return bix;
		}
	}
	return bix;
}

/**
 * logfs_seek_hole - find next hole starting at a given block index
 * @inode:		inode to search in
 * @bix:		block index to start searching
 *
 * Returns next hole.  If the file doesn't contain any further holes, the
 * block address next to eof is returned instead.
 */
u64 logfs_seek_hole(struct inode *inode, u64 bix)
{
	struct logfs_inode *li = logfs_inode(inode);

	if (bix < I0_BLOCKS) {
		bix = seek_holedata_direct(inode, bix, 0);
		if (bix < I0_BLOCKS)
			return bix;
	}

	if (!li->li_data[INDIRECT_INDEX])
		return bix;
	else if (li->li_data[INDIRECT_INDEX] & LOGFS_FULLY_POPULATED)
		bix = maxbix(li->li_height);
	else if (bix >= maxbix(li->li_height))
		return bix;
	else {
		bix = seek_holedata_loop(inode, bix, 0);
		if (bix < maxbix(li->li_height))
			return bix;
		/* Should not happen anymore.  But if some port writes semi-
		 * corrupt images (as this one used to) we might run into it.
		 */
		WARN_ON_ONCE(bix == maxbix(li->li_height));
	}

	return bix;
}

static u64 __logfs_seek_data(struct inode *inode, u64 bix)
{
	struct logfs_inode *li = logfs_inode(inode);

	if (bix < I0_BLOCKS) {
		bix = seek_holedata_direct(inode, bix, 1);
		if (bix < I0_BLOCKS)
			return bix;
	}

	if (bix < maxbix(li->li_height)) {
		if (!li->li_data[INDIRECT_INDEX])
			bix = maxbix(li->li_height);
		else
			return seek_holedata_loop(inode, bix, 1);
	}

	return bix;
}

/**
 * logfs_seek_data - find next data block after a given block index
 * @inode:		inode to search in
 * @bix:		block index to start searching
 *
 * Returns next data block.  If the file doesn't contain any further data
 * blocks, the last block in the file is returned instead.
 */
u64 logfs_seek_data(struct inode *inode, u64 bix)
{
	struct super_block *sb = inode->i_sb;
	u64 ret, end;

	ret = __logfs_seek_data(inode, bix);
	end = i_size_read(inode) >> sb->s_blocksize_bits;
	if (ret >= end)
		ret = max(bix, end);
	return ret;
}

static int logfs_is_valid_direct(struct logfs_inode *li, u64 bix, u64 ofs)
{
	return pure_ofs(li->li_data[bix]) == ofs;
}

static int __logfs_is_valid_loop(struct inode *inode, u64 bix,
		u64 ofs, u64 bofs)
{
	struct logfs_inode *li = logfs_inode(inode);
	level_t level;
	int ret;
	struct page *page;

	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)){
		page = logfs_get_write_page(inode, bix, level);
		BUG_ON(!page);

		ret = logfs_segment_read(inode, page, bofs, bix, level);
		if (ret) {
			logfs_put_write_page(page);
			return 0;
		}

		bofs = block_get_pointer(page, get_bits(bix, SUBLEVEL(level)));
		logfs_put_write_page(page);
		if (!bofs)
			return 0;

		if (pure_ofs(bofs) == ofs)
			return 1;
	}
	return 0;
}

static int logfs_is_valid_loop(struct inode *inode, u64 bix, u64 ofs)
{
	struct logfs_inode *li = logfs_inode(inode);
	u64 bofs = li->li_data[INDIRECT_INDEX];

	if (!bofs)
		return 0;

	if (bix >= maxbix(li->li_height))
		return 0;

	if (pure_ofs(bofs) == ofs)
		return 1;

	return __logfs_is_valid_loop(inode, bix, ofs, bofs);
}

static int __logfs_is_valid_block(struct inode *inode, u64 bix, u64 ofs)
{
	struct logfs_inode *li = logfs_inode(inode);

	if ((inode->i_nlink == 0) && atomic_read(&inode->i_count) == 1)
		return 0;

	if (bix < I0_BLOCKS)
		return logfs_is_valid_direct(li, bix, ofs);
	return logfs_is_valid_loop(inode, bix, ofs);
}

/**
 * logfs_is_valid_block - check whether this block is still valid
 *
 * @sb	- superblock
 * @ofs	- block physical offset
 * @ino	- block inode number
 * @bix	- block index
 * @level - block level
 *
 * Returns 0 if the block is invalid, 1 if it is valid and 2 if it will
 * become invalid once the journal is written.
 */
int logfs_is_valid_block(struct super_block *sb, u64 ofs, u64 ino, u64 bix,
		gc_level_t gc_level)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode;
	int ret, cookie;

	/* Umount closes a segment with free blocks remaining.  Those
	 * blocks are by definition invalid. */
	if (ino == -1)
		return 0;

	LOGFS_BUG_ON((u64)(u_long)ino != ino, sb);

	inode = logfs_safe_iget(sb, ino, &cookie);
	if (IS_ERR(inode))
		goto invalid;

	ret = __logfs_is_valid_block(inode, bix, ofs);
	logfs_safe_iput(inode, cookie);
	if (ret)
		return ret;

invalid:
	/* Block is nominally invalid, but may still sit in the shadow tree,
	 * waiting for a journal commit.
	 */
	if (btree_lookup64(&super->s_shadow_tree.old, ofs))
		return 2;
	return 0;
}

int logfs_readpage_nolock(struct page *page)
{
	struct inode *inode = page->mapping->host;
	int ret = -EIO;

	ret = logfs_read_block(inode, page, READ);

	if (ret) {
		ClearPageUptodate(page);
		SetPageError(page);
	} else {
		SetPageUptodate(page);
		ClearPageError(page);
	}
	flush_dcache_page(page);

	return ret;
}

static int logfs_reserve_bytes(struct inode *inode, int bytes)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	u64 available = super->s_free_bytes + super->s_dirty_free_bytes
			- super->s_dirty_used_bytes - super->s_dirty_pages;

	if (!bytes)
		return 0;

	if (available < bytes)
		return -ENOSPC;

	if (available < bytes + super->s_root_reserve &&
			!capable(CAP_SYS_RESOURCE))
		return -ENOSPC;

	return 0;
}

int get_page_reserve(struct inode *inode, struct page *page)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	struct logfs_block *block = logfs_block(page);
	int ret;

	if (block && block->reserved_bytes)
		return 0;

	logfs_get_wblocks(inode->i_sb, page, WF_LOCK);
	while ((ret = logfs_reserve_bytes(inode, 6 * LOGFS_MAX_OBJECTSIZE)) &&
			!list_empty(&super->s_writeback_list)) {
		block = list_entry(super->s_writeback_list.next,
				struct logfs_block, alias_list);
		block->ops->write_block(block);
	}
	if (!ret) {
		alloc_data_block(inode, page);
		block = logfs_block(page);
		block->reserved_bytes += 6 * LOGFS_MAX_OBJECTSIZE;
		super->s_dirty_pages += 6 * LOGFS_MAX_OBJECTSIZE;
		list_move_tail(&block->alias_list, &super->s_writeback_list);
	}
	logfs_put_wblocks(inode->i_sb, page, WF_LOCK);
	return ret;
}

/*
 * We are protected by write lock.  Push victims up to superblock level
 * and release transaction when appropriate.
 */
/* FIXME: This is currently called from the wrong spots. */
static void logfs_handle_transaction(struct inode *inode,
		struct logfs_transaction *ta)
{
	struct logfs_super *super = logfs_super(inode->i_sb);

	if (!ta)
		return;
	logfs_inode(inode)->li_block->ta = NULL;

	if (inode->i_ino != LOGFS_INO_MASTER) {
		BUG(); /* FIXME: Yes, this needs more thought */
		/* just remember the transaction until inode is written */
		//BUG_ON(logfs_inode(inode)->li_transaction);
		//logfs_inode(inode)->li_transaction = ta;
		return;
	}

	switch (ta->state) {
	case CREATE_1: /* fall through */
	case UNLINK_1:
		BUG_ON(super->s_victim_ino);
		super->s_victim_ino = ta->ino;
		break;
	case CREATE_2: /* fall through */
	case UNLINK_2:
		BUG_ON(super->s_victim_ino != ta->ino);
		super->s_victim_ino = 0;
		/* transaction ends here - free it */
		kfree(ta);
		break;
	case CROSS_RENAME_1:
		BUG_ON(super->s_rename_dir);
		BUG_ON(super->s_rename_pos);
		super->s_rename_dir = ta->dir;
		super->s_rename_pos = ta->pos;
		break;
	case CROSS_RENAME_2:
		BUG_ON(super->s_rename_dir != ta->dir);
		BUG_ON(super->s_rename_pos != ta->pos);
		super->s_rename_dir = 0;
		super->s_rename_pos = 0;
		kfree(ta);
		break;
	case TARGET_RENAME_1:
		BUG_ON(super->s_rename_dir);
		BUG_ON(super->s_rename_pos);
		BUG_ON(super->s_victim_ino);
		super->s_rename_dir = ta->dir;
		super->s_rename_pos = ta->pos;
		super->s_victim_ino = ta->ino;
		break;
	case TARGET_RENAME_2:
		BUG_ON(super->s_rename_dir != ta->dir);
		BUG_ON(super->s_rename_pos != ta->pos);
		BUG_ON(super->s_victim_ino != ta->ino);
		super->s_rename_dir = 0;
		super->s_rename_pos = 0;
		break;
	case TARGET_RENAME_3:
		BUG_ON(super->s_rename_dir);
		BUG_ON(super->s_rename_pos);
		BUG_ON(super->s_victim_ino != ta->ino);
		super->s_victim_ino = 0;
		kfree(ta);
		break;
	default:
		BUG();
	}
}

/*
 * Not strictly a reservation, but rather a check that we still have enough
 * space to satisfy the write.
 */
static int logfs_reserve_blocks(struct inode *inode, int blocks)
{
	return logfs_reserve_bytes(inode, blocks * LOGFS_MAX_OBJECTSIZE);
}

struct write_control {
	u64 ofs;
	long flags;
};

static struct logfs_shadow *alloc_shadow(struct inode *inode, u64 bix,
		level_t level, u64 old_ofs)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	struct logfs_shadow *shadow;

	shadow = mempool_alloc(super->s_shadow_pool, GFP_NOFS);
	memset(shadow, 0, sizeof(*shadow));
	shadow->ino = inode->i_ino;
	shadow->bix = bix;
	shadow->gc_level = expand_level(inode->i_ino, level);
	shadow->old_ofs = old_ofs & ~LOGFS_FULLY_POPULATED;
	return shadow;
}

static void free_shadow(struct inode *inode, struct logfs_shadow *shadow)
{
	struct logfs_super *super = logfs_super(inode->i_sb);

	mempool_free(shadow, super->s_shadow_pool);
}

static void mark_segment(struct shadow_tree *tree, u32 segno)
{
	int err;

	if (!btree_lookup32(&tree->segment_map, segno)) {
		err = btree_insert32(&tree->segment_map, segno, (void *)1,
				GFP_NOFS);
		BUG_ON(err);
		tree->no_shadowed_segments++;
	}
}

/**
 * fill_shadow_tree - Propagate shadow tree changes due to a write
 * @inode:	Inode owning the page
 * @page:	Struct page that was written
 * @shadow:	Shadow for the current write
 *
 * Writes in logfs can result in two semi-valid objects.  The old object
 * is still valid as long as it can be reached by following pointers on
 * the medium.  Only when writes propagate all the way up to the journal
 * has the new object safely replaced the old one.
 *
 * To handle this problem, a struct logfs_shadow is used to represent
 * every single write.  It is attached to the indirect block, which is
 * marked dirty.  When the indirect block is written, its shadows are
 * handed up to the next indirect block (or inode).  Untimately they
 * will reach the master inode and be freed upon journal commit.
 *
 * This function handles a single step in the propagation.  It adds the
 * shadow for the current write to the tree, along with any shadows in
 * the page's tree, in case it was an indirect block.  If a page is
 * written, the inode parameter is left NULL, if an inode is written,
 * the page parameter is left NULL.
 */
static void fill_shadow_tree(struct inode *inode, struct page *page,
		struct logfs_shadow *shadow)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	struct logfs_block *block = logfs_block(page);
	struct shadow_tree *tree = &super->s_shadow_tree;

	if (PagePrivate(page)) {
		if (block->alias_map)
			super->s_no_object_aliases -= bitmap_weight(
					block->alias_map, LOGFS_BLOCK_FACTOR);
		logfs_handle_transaction(inode, block->ta);
		block->ops->free_block(inode->i_sb, block);
	}
	if (shadow) {
		if (shadow->old_ofs)
			btree_insert64(&tree->old, shadow->old_ofs, shadow,
					GFP_NOFS);
		else
			btree_insert64(&tree->new, shadow->new_ofs, shadow,
					GFP_NOFS);

		super->s_dirty_used_bytes += shadow->new_len;
		super->s_dirty_free_bytes += shadow->old_len;
		mark_segment(tree, shadow->old_ofs >> super->s_segshift);
		mark_segment(tree, shadow->new_ofs >> super->s_segshift);
	}
}

static void logfs_set_alias(struct super_block *sb, struct logfs_block *block,
		long child_no)
{
	struct logfs_super *super = logfs_super(sb);

	if (block->inode && block->inode->i_ino == LOGFS_INO_MASTER) {
		/* Aliases in the master inode are pointless. */
		return;
	}

	if (!test_bit(child_no, block->alias_map)) {
		set_bit(child_no, block->alias_map);
		super->s_no_object_aliases++;
	}
	list_move_tail(&block->alias_list, &super->s_object_alias);
}

/*
 * Object aliases can and often do change the size and occupied space of a
 * file.  So not only do we have to change the pointers, we also have to
 * change inode->i_size and li->li_used_bytes.  Which is done by setting
 * another two object aliases for the inode itself.
 */
static void set_iused(struct inode *inode, struct logfs_shadow *shadow)
{
	struct logfs_inode *li = logfs_inode(inode);

	if (shadow->new_len == shadow->old_len)
		return;

	alloc_inode_block(inode);
	li->li_used_bytes += shadow->new_len - shadow->old_len;
	__logfs_set_blocks(inode);
	logfs_set_alias(inode->i_sb, li->li_block, INODE_USED_OFS);
	logfs_set_alias(inode->i_sb, li->li_block, INODE_SIZE_OFS);
}

static int logfs_write_i0(struct inode *inode, struct page *page,
		struct write_control *wc)
{
	struct logfs_shadow *shadow;
	u64 bix;
	level_t level;
	int full, err = 0;

	logfs_unpack_index(page->index, &bix, &level);
	if (wc->ofs == 0)
		if (logfs_reserve_blocks(inode, 1))
			return -ENOSPC;

	shadow = alloc_shadow(inode, bix, level, wc->ofs);
	if (wc->flags & WF_WRITE)
		err = logfs_segment_write(inode, page, shadow);
	if (wc->flags & WF_DELETE)
		logfs_segment_delete(inode, shadow);
	if (err) {
		free_shadow(inode, shadow);
		return err;
	}

	set_iused(inode, shadow);
	full = 1;
	if (level != 0) {
		alloc_indirect_block(inode, page, 0);
		full = logfs_block(page)->full == LOGFS_BLOCK_FACTOR;
	}
	fill_shadow_tree(inode, page, shadow);
	wc->ofs = shadow->new_ofs;
	if (wc->ofs && full)
		wc->ofs |= LOGFS_FULLY_POPULATED;
	return 0;
}

static int logfs_write_direct(struct inode *inode, struct page *page,
		long flags)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct write_control wc = {
		.ofs = li->li_data[page->index],
		.flags = flags,
	};
	int err;

	alloc_inode_block(inode);

	err = logfs_write_i0(inode, page, &wc);
	if (err)
		return err;

	li->li_data[page->index] = wc.ofs;
	logfs_set_alias(inode->i_sb, li->li_block,
			page->index + INODE_POINTER_OFS);
	return 0;
}

static int ptr_change(u64 ofs, struct page *page)
{
	struct logfs_block *block = logfs_block(page);
	int empty0, empty1, full0, full1;

	empty0 = ofs == 0;
	empty1 = block->partial == 0;
	if (empty0 != empty1)
		return 1;

	/* The !! is necessary to shrink result to int */
	full0 = !!(ofs & LOGFS_FULLY_POPULATED);
	full1 = block->full == LOGFS_BLOCK_FACTOR;
	if (full0 != full1)
		return 1;
	return 0;
}

static int __logfs_write_rec(struct inode *inode, struct page *page,
		struct write_control *this_wc,
		pgoff_t bix, level_t target_level, level_t level)
{
	int ret, page_empty = 0;
	int child_no = get_bits(bix, SUBLEVEL(level));
	struct page *ipage;
	struct write_control child_wc = {
		.flags = this_wc->flags,
	};

	ipage = logfs_get_write_page(inode, bix, level);
	if (!ipage)
		return -ENOMEM;

	if (this_wc->ofs) {
		ret = logfs_segment_read(inode, ipage, this_wc->ofs, bix, level);
		if (ret)
			goto out;
	} else if (!PageUptodate(ipage)) {
		page_empty = 1;
		logfs_read_empty(ipage);
	}

	child_wc.ofs = block_get_pointer(ipage, child_no);

	if ((__force u8)level-1 > (__force u8)target_level)
		ret = __logfs_write_rec(inode, page, &child_wc, bix,
				target_level, SUBLEVEL(level));
	else
		ret = logfs_write_i0(inode, page, &child_wc);

	if (ret)
		goto out;

	alloc_indirect_block(inode, ipage, page_empty);
	block_set_pointer(ipage, child_no, child_wc.ofs);
	/* FIXME: first condition seems superfluous */
	if (child_wc.ofs || logfs_block(ipage)->partial)
		this_wc->flags |= WF_WRITE;
	/* the condition on this_wc->ofs ensures that we won't consume extra
	 * space for indirect blocks in the future, which we cannot reserve */
	if (!this_wc->ofs || ptr_change(this_wc->ofs, ipage))
		ret = logfs_write_i0(inode, ipage, this_wc);
	else
		logfs_set_alias(inode->i_sb, logfs_block(ipage), child_no);
out:
	logfs_put_write_page(ipage);
	return ret;
}

static int logfs_write_rec(struct inode *inode, struct page *page,
		pgoff_t bix, level_t target_level, long flags)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct write_control wc = {
		.ofs = li->li_data[INDIRECT_INDEX],
		.flags = flags,
	};
	int ret;

	alloc_inode_block(inode);

	if (li->li_height > (__force u8)target_level)
		ret = __logfs_write_rec(inode, page, &wc, bix, target_level,
				LEVEL(li->li_height));
	else
		ret = logfs_write_i0(inode, page, &wc);
	if (ret)
		return ret;

	if (li->li_data[INDIRECT_INDEX] != wc.ofs) {
		li->li_data[INDIRECT_INDEX] = wc.ofs;
		logfs_set_alias(inode->i_sb, li->li_block,
				INDIRECT_INDEX + INODE_POINTER_OFS);
	}
	return ret;
}

void logfs_add_transaction(struct inode *inode, struct logfs_transaction *ta)
{
	alloc_inode_block(inode);
	logfs_inode(inode)->li_block->ta = ta;
}

void logfs_del_transaction(struct inode *inode, struct logfs_transaction *ta)
{
	struct logfs_block *block = logfs_inode(inode)->li_block;

	if (block && block->ta)
		block->ta = NULL;
}

static int grow_inode(struct inode *inode, u64 bix, level_t level)
{
	struct logfs_inode *li = logfs_inode(inode);
	u8 height = (__force u8)level;
	struct page *page;
	struct write_control wc = {
		.flags = WF_WRITE,
	};
	int err;

	BUG_ON(height > 5 || li->li_height > 5);
	while (height > li->li_height || bix >= maxbix(li->li_height)) {
		page = logfs_get_write_page(inode, I0_BLOCKS + 1,
				LEVEL(li->li_height + 1));
		if (!page)
			return -ENOMEM;
		logfs_read_empty(page);
		alloc_indirect_block(inode, page, 1);
		block_set_pointer(page, 0, li->li_data[INDIRECT_INDEX]);
		err = logfs_write_i0(inode, page, &wc);
		logfs_put_write_page(page);
		if (err)
			return err;
		li->li_data[INDIRECT_INDEX] = wc.ofs;
		wc.ofs = 0;
		li->li_height++;
		logfs_set_alias(inode->i_sb, li->li_block, INODE_HEIGHT_OFS);
	}
	return 0;
}

static int __logfs_write_buf(struct inode *inode, struct page *page, long flags)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	pgoff_t index = page->index;
	u64 bix;
	level_t level;
	int err;

	flags |= WF_WRITE | WF_DELETE;
	inode->i_ctime = inode->i_mtime = CURRENT_TIME;

	logfs_unpack_index(index, &bix, &level);
	if (logfs_block(page) && logfs_block(page)->reserved_bytes)
		super->s_dirty_pages -= logfs_block(page)->reserved_bytes;

	if (index < I0_BLOCKS)
		return logfs_write_direct(inode, page, flags);

	bix = adjust_bix(bix, level);
	err = grow_inode(inode, bix, level);
	if (err)
		return err;
	return logfs_write_rec(inode, page, bix, level, flags);
}

int logfs_write_buf(struct inode *inode, struct page *page, long flags)
{
	struct super_block *sb = inode->i_sb;
	int ret;

	logfs_get_wblocks(sb, page, flags & WF_LOCK);
	ret = __logfs_write_buf(inode, page, flags);
	logfs_put_wblocks(sb, page, flags & WF_LOCK);
	return ret;
}

static int __logfs_delete(struct inode *inode, struct page *page)
{
	long flags = WF_DELETE;
	int err;

	inode->i_ctime = inode->i_mtime = CURRENT_TIME;

	if (page->index < I0_BLOCKS)
		return logfs_write_direct(inode, page, flags);
	err = grow_inode(inode, page->index, 0);
	if (err)
		return err;
	return logfs_write_rec(inode, page, page->index, 0, flags);
}

int logfs_delete(struct inode *inode, pgoff_t index,
		struct shadow_tree *shadow_tree)
{
	struct super_block *sb = inode->i_sb;
	struct page *page;
	int ret;

	page = logfs_get_read_page(inode, index, 0);
	if (!page)
		return -ENOMEM;

	logfs_get_wblocks(sb, page, 1);
	ret = __logfs_delete(inode, page);
	logfs_put_wblocks(sb, page, 1);

	logfs_put_read_page(page);

	return ret;
}

int logfs_rewrite_block(struct inode *inode, u64 bix, u64 ofs,
		gc_level_t gc_level, long flags)
{
	level_t level = shrink_level(gc_level);
	struct page *page;
	int err;

	page = logfs_get_write_page(inode, bix, level);
	if (!page)
		return -ENOMEM;

	err = logfs_segment_read(inode, page, ofs, bix, level);
	if (!err) {
		if (level != 0)
			alloc_indirect_block(inode, page, 0);
		err = logfs_write_buf(inode, page, flags);
		if (!err && shrink_level(gc_level) == 0) {
			/* Rewrite cannot mark the inode dirty but has to
			 * write it immediately.
			 * Q: Can't we just create an alias for the inode
			 * instead?  And if not, why not?
			 */
			if (inode->i_ino == LOGFS_INO_MASTER)
				logfs_write_anchor(inode->i_sb);
			else {
				err = __logfs_write_inode(inode, page, flags);
			}
		}
	}
	logfs_put_write_page(page);
	return err;
}

static int truncate_data_block(struct inode *inode, struct page *page,
		u64 ofs, struct logfs_shadow *shadow, u64 size)
{
	loff_t pageofs = page->index << inode->i_sb->s_blocksize_bits;
	u64 bix;
	level_t level;
	int err;

	/* Does truncation happen within this page? */
	if (size <= pageofs || size - pageofs >= PAGE_SIZE)
		return 0;

	logfs_unpack_index(page->index, &bix, &level);
	BUG_ON(level != 0);

	err = logfs_segment_read(inode, page, ofs, bix, level);
	if (err)
		return err;

	zero_user_segment(page, size - pageofs, PAGE_CACHE_SIZE);
	return logfs_segment_write(inode, page, shadow);
}

static int logfs_truncate_i0(struct inode *inode, struct page *page,
		struct write_control *wc, u64 size)
{
	struct logfs_shadow *shadow;
	u64 bix;
	level_t level;
	int err = 0;

	logfs_unpack_index(page->index, &bix, &level);
	BUG_ON(level != 0);
	shadow = alloc_shadow(inode, bix, level, wc->ofs);

	err = truncate_data_block(inode, page, wc->ofs, shadow, size);
	if (err) {
		free_shadow(inode, shadow);
		return err;
	}

	logfs_segment_delete(inode, shadow);
	set_iused(inode, shadow);
	fill_shadow_tree(inode, page, shadow);
	wc->ofs = shadow->new_ofs;
	return 0;
}

static int logfs_truncate_direct(struct inode *inode, u64 size)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct write_control wc;
	struct page *page;
	int e;
	int err;

	alloc_inode_block(inode);

	for (e = I0_BLOCKS - 1; e >= 0; e--) {
		if (size > (e+1) * LOGFS_BLOCKSIZE)
			break;

		wc.ofs = li->li_data[e];
		if (!wc.ofs)
			continue;

		page = logfs_get_write_page(inode, e, 0);
		if (!page)
			return -ENOMEM;
		err = logfs_segment_read(inode, page, wc.ofs, e, 0);
		if (err) {
			logfs_put_write_page(page);
			return err;
		}
		err = logfs_truncate_i0(inode, page, &wc, size);
		logfs_put_write_page(page);
		if (err)
			return err;

		li->li_data[e] = wc.ofs;
	}
	return 0;
}

/* FIXME: these need to become per-sb once we support different blocksizes */
static u64 __logfs_step[] = {
	1,
	I1_BLOCKS,
	I2_BLOCKS,
	I3_BLOCKS,
};

static u64 __logfs_start_index[] = {
	I0_BLOCKS,
	I1_BLOCKS,
	I2_BLOCKS,
	I3_BLOCKS
};

static inline u64 logfs_step(level_t level)
{
	return __logfs_step[(__force u8)level];
}

static inline u64 logfs_factor(u8 level)
{
	return __logfs_step[level] * LOGFS_BLOCKSIZE;
}

static inline u64 logfs_start_index(level_t level)
{
	return __logfs_start_index[(__force u8)level];
}

static void logfs_unpack_raw_index(pgoff_t index, u64 *bix, level_t *level)
{
	logfs_unpack_index(index, bix, level);
	if (*bix <= logfs_start_index(SUBLEVEL(*level)))
		*bix = 0;
}

static int __logfs_truncate_rec(struct inode *inode, struct page *ipage,
		struct write_control *this_wc, u64 size)
{
	int truncate_happened = 0;
	int e, err = 0;
	u64 bix, child_bix, next_bix;
	level_t level;
	struct page *page;
	struct write_control child_wc = { /* FIXME: flags */ };

	logfs_unpack_raw_index(ipage->index, &bix, &level);
	err = logfs_segment_read(inode, ipage, this_wc->ofs, bix, level);
	if (err)
		return err;

	for (e = LOGFS_BLOCK_FACTOR - 1; e >= 0; e--) {
		child_bix = bix + e * logfs_step(SUBLEVEL(level));
		next_bix = child_bix + logfs_step(SUBLEVEL(level));
		if (size > next_bix * LOGFS_BLOCKSIZE)
			break;

		child_wc.ofs = pure_ofs(block_get_pointer(ipage, e));
		if (!child_wc.ofs)
			continue;

		page = logfs_get_write_page(inode, child_bix, SUBLEVEL(level));
		if (!page)
			return -ENOMEM;

		if ((__force u8)level > 1)
			err = __logfs_truncate_rec(inode, page, &child_wc, size);
		else
			err = logfs_truncate_i0(inode, page, &child_wc, size);
		logfs_put_write_page(page);
		if (err)
			return err;

		truncate_happened = 1;
		alloc_indirect_block(inode, ipage, 0);
		block_set_pointer(ipage, e, child_wc.ofs);
	}

	if (!truncate_happened) {
		printk("ineffectual truncate (%lx, %lx, %llx)\n", inode->i_ino, ipage->index, size);
		return 0;
	}

	this_wc->flags = WF_DELETE;
	if (logfs_block(ipage)->partial)
		this_wc->flags |= WF_WRITE;

	return logfs_write_i0(inode, ipage, this_wc);
}

static int logfs_truncate_rec(struct inode *inode, u64 size)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct write_control wc = {
		.ofs = li->li_data[INDIRECT_INDEX],
	};
	struct page *page;
	int err;

	alloc_inode_block(inode);

	if (!wc.ofs)
		return 0;

	page = logfs_get_write_page(inode, 0, LEVEL(li->li_height));
	if (!page)
		return -ENOMEM;

	err = __logfs_truncate_rec(inode, page, &wc, size);
	logfs_put_write_page(page);
	if (err)
		return err;

	if (li->li_data[INDIRECT_INDEX] != wc.ofs)
		li->li_data[INDIRECT_INDEX] = wc.ofs;
	return 0;
}

static int __logfs_truncate(struct inode *inode, u64 size)
{
	int ret;

	if (size >= logfs_factor(logfs_inode(inode)->li_height))
		return 0;

	ret = logfs_truncate_rec(inode, size);
	if (ret)
		return ret;

	return logfs_truncate_direct(inode, size);
}

/*
 * Truncate, by changing the segment file, can consume a fair amount
 * of resources.  So back off from time to time and do some GC.
 * 8 or 2048 blocks should be well within safety limits even if
 * every single block resided in a different segment.
 */
#define TRUNCATE_STEP	(8 * 1024 * 1024)
int logfs_truncate(struct inode *inode, u64 target)
{
	struct super_block *sb = inode->i_sb;
	u64 size = i_size_read(inode);
	int err = 0;

	size = ALIGN(size, TRUNCATE_STEP);
	while (size > target) {
		if (size > TRUNCATE_STEP)
			size -= TRUNCATE_STEP;
		else
			size = 0;
		if (size < target)
			size = target;

		logfs_get_wblocks(sb, NULL, 1);
		err = __logfs_truncate(inode, size);
		if (!err)
			err = __logfs_write_inode(inode, NULL, 0);
		logfs_put_wblocks(sb, NULL, 1);
	}

	if (!err) {
		err = inode_newsize_ok(inode, target);
		if (err)
			goto out;

		truncate_setsize(inode, target);
	}

 out:
	/* I don't trust error recovery yet. */
	WARN_ON(err);
	return err;
}

static void move_page_to_inode(struct inode *inode, struct page *page)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct logfs_block *block = logfs_block(page);

	if (!block)
		return;

	log_blockmove("move_page_to_inode(%llx, %llx, %x)\n",
			block->ino, block->bix, block->level);
	BUG_ON(li->li_block);
	block->ops = &inode_block_ops;
	block->inode = inode;
	li->li_block = block;

	block->page = NULL;
	if (PagePrivate(page)) {
		ClearPagePrivate(page);
		page_cache_release(page);
		set_page_private(page, 0);
	}
}

static void move_inode_to_page(struct page *page, struct inode *inode)
{
	struct logfs_inode *li = logfs_inode(inode);
	struct logfs_block *block = li->li_block;

	if (!block)
		return;

	log_blockmove("move_inode_to_page(%llx, %llx, %x)\n",
			block->ino, block->bix, block->level);
	BUG_ON(PagePrivate(page));
	block->ops = &indirect_block_ops;
	block->page = page;

	if (!PagePrivate(page)) {
		SetPagePrivate(page);
		page_cache_get(page);
		set_page_private(page, (unsigned long) block);
	}

	block->inode = NULL;
	li->li_block = NULL;
}

int logfs_read_inode(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_super *super = logfs_super(sb);
	struct inode *master_inode = super->s_master_inode;
	struct page *page;
	struct logfs_disk_inode *di;
	u64 ino = inode->i_ino;

	if (ino << sb->s_blocksize_bits > i_size_read(master_inode))
		return -ENODATA;
	if (!logfs_exist_block(master_inode, ino))
		return -ENODATA;

	page = read_cache_page(master_inode->i_mapping, ino,
			(filler_t *)logfs_readpage, NULL);
	if (IS_ERR(page))
		return PTR_ERR(page);

	di = kmap_atomic(page);
	logfs_disk_to_inode(di, inode);
	kunmap_atomic(di);
	move_page_to_inode(inode, page);
	page_cache_release(page);
	return 0;
}

/* Caller must logfs_put_write_page(page); */
static struct page *inode_to_page(struct inode *inode)
{
	struct inode *master_inode = logfs_super(inode->i_sb)->s_master_inode;
	struct logfs_disk_inode *di;
	struct page *page;

	BUG_ON(inode->i_ino == LOGFS_INO_MASTER);

	page = logfs_get_write_page(master_inode, inode->i_ino, 0);
	if (!page)
		return NULL;

	di = kmap_atomic(page);
	logfs_inode_to_disk(inode, di);
	kunmap_atomic(di);
	move_inode_to_page(page, inode);
	return page;
}

static int do_write_inode(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct inode *master_inode = logfs_super(sb)->s_master_inode;
	loff_t size = (inode->i_ino + 1) << inode->i_sb->s_blocksize_bits;
	struct page *page;
	int err;

	BUG_ON(inode->i_ino == LOGFS_INO_MASTER);
	/* FIXME: lock inode */

	if (i_size_read(master_inode) < size)
		i_size_write(master_inode, size);

	/* TODO: Tell vfs this inode is clean now */

	page = inode_to_page(inode);
	if (!page)
		return -ENOMEM;

	/* FIXME: transaction is part of logfs_block now.  Is that enough? */
	err = logfs_write_buf(master_inode, page, 0);
	if (err)
		move_page_to_inode(inode, page);

	logfs_put_write_page(page);
	return err;
}

static void logfs_mod_segment_entry(struct super_block *sb, u32 segno,
		int write,
		void (*change_se)(struct logfs_segment_entry *, long),
		long arg)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode;
	struct page *page;
	struct logfs_segment_entry *se;
	pgoff_t page_no;
	int child_no;

	page_no = segno >> (sb->s_blocksize_bits - 3);
	child_no = segno & ((sb->s_blocksize >> 3) - 1);

	inode = super->s_segfile_inode;
	page = logfs_get_write_page(inode, page_no, 0);
	BUG_ON(!page); /* FIXME: We need some reserve page for this case */
	if (!PageUptodate(page))
		logfs_read_block(inode, page, WRITE);

	if (write)
		alloc_indirect_block(inode, page, 0);
	se = kmap_atomic(page);
	change_se(se + child_no, arg);
	if (write) {
		logfs_set_alias(sb, logfs_block(page), child_no);
		BUG_ON((int)be32_to_cpu(se[child_no].valid) > super->s_segsize);
	}
	kunmap_atomic(se);

	logfs_put_write_page(page);
}

static void __get_segment_entry(struct logfs_segment_entry *se, long _target)
{
	struct logfs_segment_entry *target = (void *)_target;

	*target = *se;
}

void logfs_get_segment_entry(struct super_block *sb, u32 segno,
		struct logfs_segment_entry *se)
{
	logfs_mod_segment_entry(sb, segno, 0, __get_segment_entry, (long)se);
}

static void __set_segment_used(struct logfs_segment_entry *se, long increment)
{
	u32 valid;

	valid = be32_to_cpu(se->valid);
	valid += increment;
	se->valid = cpu_to_be32(valid);
}

void logfs_set_segment_used(struct super_block *sb, u64 ofs, int increment)
{
	struct logfs_super *super = logfs_super(sb);
	u32 segno = ofs >> super->s_segshift;

	if (!increment)
		return;

	logfs_mod_segment_entry(sb, segno, 1, __set_segment_used, increment);
}

static void __set_segment_erased(struct logfs_segment_entry *se, long ec_level)
{
	se->ec_level = cpu_to_be32(ec_level);
}

void logfs_set_segment_erased(struct super_block *sb, u32 segno, u32 ec,
		gc_level_t gc_level)
{
	u32 ec_level = ec << 4 | (__force u8)gc_level;

	logfs_mod_segment_entry(sb, segno, 1, __set_segment_erased, ec_level);
}

static void __set_segment_reserved(struct logfs_segment_entry *se, long ignore)
{
	se->valid = cpu_to_be32(RESERVED);
}

void logfs_set_segment_reserved(struct super_block *sb, u32 segno)
{
	logfs_mod_segment_entry(sb, segno, 1, __set_segment_reserved, 0);
}

static void __set_segment_unreserved(struct logfs_segment_entry *se,
		long ec_level)
{
	se->valid = 0;
	se->ec_level = cpu_to_be32(ec_level);
}

void logfs_set_segment_unreserved(struct super_block *sb, u32 segno, u32 ec)
{
	u32 ec_level = ec << 4;

	logfs_mod_segment_entry(sb, segno, 1, __set_segment_unreserved,
			ec_level);
}

int __logfs_write_inode(struct inode *inode, struct page *page, long flags)
{
	struct super_block *sb = inode->i_sb;
	int ret;

	logfs_get_wblocks(sb, page, flags & WF_LOCK);
	ret = do_write_inode(inode);
	logfs_put_wblocks(sb, page, flags & WF_LOCK);
	return ret;
}

static int do_delete_inode(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct inode *master_inode = logfs_super(sb)->s_master_inode;
	struct page *page;
	int ret;

	page = logfs_get_write_page(master_inode, inode->i_ino, 0);
	if (!page)
		return -ENOMEM;

	move_inode_to_page(page, inode);

	logfs_get_wblocks(sb, page, 1);
	ret = __logfs_delete(master_inode, page);
	logfs_put_wblocks(sb, page, 1);

	logfs_put_write_page(page);
	return ret;
}

/*
 * ZOMBIE inodes have already been deleted before and should remain dead,
 * if it weren't for valid checking.  No need to kill them again here.
 */
void logfs_evict_inode(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_inode *li = logfs_inode(inode);
	struct logfs_block *block = li->li_block;
	struct page *page;

	if (!inode->i_nlink) {
		if (!(li->li_flags & LOGFS_IF_ZOMBIE)) {
			li->li_flags |= LOGFS_IF_ZOMBIE;
			if (i_size_read(inode) > 0)
				logfs_truncate(inode, 0);
			do_delete_inode(inode);
		}
	}
	truncate_inode_pages(&inode->i_data, 0);
	clear_inode(inode);

	/* Cheaper version of write_inode.  All changes are concealed in
	 * aliases, which are moved back.  No write to the medium happens.
	 */
	/* Only deleted files may be dirty at this point */
	BUG_ON(inode->i_state & I_DIRTY && inode->i_nlink);
	if (!block)
		return;
	if ((logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN)) {
		block->ops->free_block(inode->i_sb, block);
		return;
	}

	page = inode_to_page(inode);
	BUG_ON(!page); /* FIXME: Use emergency page */
	logfs_put_write_page(page);
}

void btree_write_block(struct logfs_block *block)
{
	struct inode *inode;
	struct page *page;
	int err, cookie;

	inode = logfs_safe_iget(block->sb, block->ino, &cookie);
	page = logfs_get_write_page(inode, block->bix, block->level);

	err = logfs_readpage_nolock(page);
	BUG_ON(err);
	BUG_ON(!PagePrivate(page));
	BUG_ON(logfs_block(page) != block);
	err = __logfs_write_buf(inode, page, 0);
	BUG_ON(err);
	BUG_ON(PagePrivate(page) || page->private);

	logfs_put_write_page(page);
	logfs_safe_iput(inode, cookie);
}

/**
 * logfs_inode_write - write inode or dentry objects
 *
 * @inode:		parent inode (ifile or directory)
 * @buf:		object to write (inode or dentry)
 * @n:			object size
 * @_pos:		object number (file position in blocks/objects)
 * @flags:		write flags
 * @lock:		0 if write lock is already taken, 1 otherwise
 * @shadow_tree:	shadow below this inode
 *
 * FIXME: All caller of this put a 200-300 byte variable on the stack,
 * only to call here and do a memcpy from that stack variable.  A good
 * example of wasted performance and stack space.
 */
int logfs_inode_write(struct inode *inode, const void *buf, size_t count,
		loff_t bix, long flags, struct shadow_tree *shadow_tree)
{
	loff_t pos = bix << inode->i_sb->s_blocksize_bits;
	int err;
	struct page *page;
	void *pagebuf;

	BUG_ON(pos & (LOGFS_BLOCKSIZE-1));
	BUG_ON(count > LOGFS_BLOCKSIZE);
	page = logfs_get_write_page(inode, bix, 0);
	if (!page)
		return -ENOMEM;

	pagebuf = kmap_atomic(page);
	memcpy(pagebuf, buf, count);
	flush_dcache_page(page);
	kunmap_atomic(pagebuf);

	if (i_size_read(inode) < pos + LOGFS_BLOCKSIZE)
		i_size_write(inode, pos + LOGFS_BLOCKSIZE);

	err = logfs_write_buf(inode, page, flags);
	logfs_put_write_page(page);
	return err;
}

int logfs_open_segfile(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode;

	inode = logfs_read_meta_inode(sb, LOGFS_INO_SEGFILE);
	if (IS_ERR(inode))
		return PTR_ERR(inode);
	super->s_segfile_inode = inode;
	return 0;
}

int logfs_init_rw(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int min_fill = 3 * super->s_no_blocks;

	INIT_LIST_HEAD(&super->s_object_alias);
	INIT_LIST_HEAD(&super->s_writeback_list);
	mutex_init(&super->s_write_mutex);
	super->s_block_pool = mempool_create_kmalloc_pool(min_fill,
			sizeof(struct logfs_block));
	super->s_shadow_pool = mempool_create_kmalloc_pool(min_fill,
			sizeof(struct logfs_shadow));
	return 0;
}

void logfs_cleanup_rw(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);

	logfs_mempool_destroy(super->s_block_pool);
	logfs_mempool_destroy(super->s_shadow_pool);
}