Commit 81def6b9862764924a99ac1b680e73ac8c80ac64
1 parent
1932191726
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Simplify and fix pad_wbuf
A comment in the old code read:
/* The math in this function can surely use some love */
And indeed it did. In the case that area->a_used_bytes is exactly
4096 bytes below segment size it fell apart. pad_wbuf is now split
into two helpers that are significantly less complicated.
Signed-off-by: Joern Engel <joern@logfs.org>
Showing 1 changed file with 30 additions and 22 deletions Side-by-side Diff
fs/logfs/segment.c
| ... | ... | @@ -93,47 +93,55 @@ |
| 93 | 93 | } while (len); |
| 94 | 94 | } |
| 95 | 95 | |
| 96 | -/* | |
| 97 | - * bdev_writeseg will write full pages. Memset the tail to prevent data leaks. | |
| 98 | - */ | |
| 99 | -static void pad_wbuf(struct logfs_area *area, int final) | |
| 96 | +static void pad_partial_page(struct logfs_area *area) | |
| 100 | 97 | { |
| 101 | 98 | struct super_block *sb = area->a_sb; |
| 102 | - struct logfs_super *super = logfs_super(sb); | |
| 103 | 99 | struct page *page; |
| 104 | 100 | u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes); |
| 105 | 101 | pgoff_t index = ofs >> PAGE_SHIFT; |
| 106 | 102 | long offset = ofs & (PAGE_SIZE-1); |
| 107 | 103 | u32 len = PAGE_SIZE - offset; |
| 108 | 104 | |
| 109 | - if (len == PAGE_SIZE) { | |
| 110 | - /* The math in this function can surely use some love */ | |
| 111 | - len = 0; | |
| 112 | - } | |
| 113 | - if (len) { | |
| 114 | - BUG_ON(area->a_used_bytes >= super->s_segsize); | |
| 115 | - | |
| 116 | - page = get_mapping_page(area->a_sb, index, 0); | |
| 105 | + if (len % PAGE_SIZE) { | |
| 106 | + page = get_mapping_page(sb, index, 0); | |
| 117 | 107 | BUG_ON(!page); /* FIXME: reserve a pool */ |
| 118 | 108 | memset(page_address(page) + offset, 0xff, len); |
| 119 | 109 | SetPagePrivate(page); |
| 120 | 110 | page_cache_release(page); |
| 121 | 111 | } |
| 112 | +} | |
| 122 | 113 | |
| 123 | - if (!final) | |
| 124 | - return; | |
| 114 | +static void pad_full_pages(struct logfs_area *area) | |
| 115 | +{ | |
| 116 | + struct super_block *sb = area->a_sb; | |
| 117 | + struct logfs_super *super = logfs_super(sb); | |
| 118 | + u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes); | |
| 119 | + u32 len = super->s_segsize - area->a_used_bytes; | |
| 120 | + pgoff_t index = PAGE_CACHE_ALIGN(ofs) >> PAGE_CACHE_SHIFT; | |
| 121 | + pgoff_t no_indizes = len >> PAGE_CACHE_SHIFT; | |
| 122 | + struct page *page; | |
| 125 | 123 | |
| 126 | - area->a_used_bytes += len; | |
| 127 | - for ( ; area->a_used_bytes < super->s_segsize; | |
| 128 | - area->a_used_bytes += PAGE_SIZE) { | |
| 129 | - /* Memset another page */ | |
| 130 | - index++; | |
| 131 | - page = get_mapping_page(area->a_sb, index, 0); | |
| 124 | + while (no_indizes) { | |
| 125 | + page = get_mapping_page(sb, index, 0); | |
| 132 | 126 | BUG_ON(!page); /* FIXME: reserve a pool */ |
| 133 | - memset(page_address(page), 0xff, PAGE_SIZE); | |
| 127 | + SetPageUptodate(page); | |
| 128 | + memset(page_address(page), 0xff, PAGE_CACHE_SIZE); | |
| 134 | 129 | SetPagePrivate(page); |
| 135 | 130 | page_cache_release(page); |
| 131 | + index++; | |
| 132 | + no_indizes--; | |
| 136 | 133 | } |
| 134 | +} | |
| 135 | + | |
| 136 | +/* | |
| 137 | + * bdev_writeseg will write full pages. Memset the tail to prevent data leaks. | |
| 138 | + * Also make sure we allocate (and memset) all pages for final writeout. | |
| 139 | + */ | |
| 140 | +static void pad_wbuf(struct logfs_area *area, int final) | |
| 141 | +{ | |
| 142 | + pad_partial_page(area); | |
| 143 | + if (final) | |
| 144 | + pad_full_pages(area); | |
| 137 | 145 | } |
| 138 | 146 | |
| 139 | 147 | /* |