Doug / smarc-fsl-linux-kernel

Download as
Browse Code ยป

Commit ed8b752bccf2560e305e25125721d2f0ac759e88

Authored by Mike Snitzer
Committed by Alasdair G Kergon
1 parent 772ae5f54d
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

dm table: set flush capability based on underlying devices 

DM has always advertised both REQ_FLUSH and REQ_FUA flush capabilities
regardless of whether or not a given DM device's underlying devices
also advertised a need for them.

Block's flush-merge changes from 2.6.39 have proven to be more costly
for DM devices.  Performance regressions have been reported even when
DM's underlying devices do not advertise that they have a write cache.

Fix the performance regressions by configuring a DM device's flushing
capabilities based on those of the underlying devices' capabilities.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Showing 2 changed files with 43 additions and 1 deletions Side-by-side Diff

drivers/md/dm-table.c
Diff comments   View file @ ed8b752
... ... @@ -1248,9 +1248,45 @@
1248 1248 blk_get_integrity(template_disk));
1249 1249 }
1250 1250  
  1251 +static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev,
  1252 + sector_t start, sector_t len, void *data)
  1253 +{
  1254 + unsigned flush = (*(unsigned *)data);
  1255 + struct request_queue *q = bdev_get_queue(dev->bdev);
  1256 +
  1257 + return q && (q->flush_flags & flush);
  1258 +}
  1259 +
  1260 +static bool dm_table_supports_flush(struct dm_table *t, unsigned flush)
  1261 +{
  1262 + struct dm_target *ti;
  1263 + unsigned i = 0;
  1264 +
  1265 + /*
  1266 + * Require at least one underlying device to support flushes.
  1267 + * t->devices includes internal dm devices such as mirror logs
  1268 + * so we need to use iterate_devices here, which targets
  1269 + * supporting flushes must provide.
  1270 + */
  1271 + while (i < dm_table_get_num_targets(t)) {
  1272 + ti = dm_table_get_target(t, i++);
  1273 +
  1274 + if (!ti->num_flush_requests)
  1275 + continue;
  1276 +
  1277 + if (ti->type->iterate_devices &&
  1278 + ti->type->iterate_devices(ti, device_flush_capable, &flush))
  1279 + return 1;
  1280 + }
  1281 +
  1282 + return 0;
  1283 +}
  1284 +
1251 1285 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
1252 1286 struct queue_limits *limits)
1253 1287 {
  1288 + unsigned flush = 0;
  1289 +
1254 1290 /*
1255 1291 * Copy table's limits to the DM device's request_queue
1256 1292 */
... ... @@ -1260,6 +1296,13 @@
1260 1296 queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
1261 1297 else
1262 1298 queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
  1299 +
  1300 + if (dm_table_supports_flush(t, REQ_FLUSH)) {
  1301 + flush |= REQ_FLUSH;
  1302 + if (dm_table_supports_flush(t, REQ_FUA))
  1303 + flush |= REQ_FUA;
  1304 + }
  1305 + blk_queue_flush(q, flush);
1263 1306  
1264 1307 dm_table_set_integrity(t);
1265 1308  
... ... @@ -1808,7 +1808,6 @@
1808 1808 blk_queue_make_request(md->queue, dm_request);
1809 1809 blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
1810 1810 blk_queue_merge_bvec(md->queue, dm_merge_bvec);
1811   - blk_queue_flush(md->queue, REQ_FLUSH | REQ_FUA);
1812 1811 }
1813 1812  
1814 1813 /*