>>>>> "Shaohua" == Shaohua Li <s...@fb.com> writes:
Shaohua> blkdev_issue_zeroout try discard/writesame first, if they fail,
Shaohua> zeroout fallback to regular write. The problem is
Shaohua> discard/writesame doesn't return error for -EOPNOTSUPP, then
Shaohua> zeroout can't do fallback and leave disk data not
Shaohua> changed. zeroout should have guaranteed zero-fill behavior.
As discussed at LSF/MM, let's explicitly separate the exported/ioctl()
functions from the __/do_foo_bar iterators. That's essentially what you
have done. And then put all error handling and policy in the ioctl()
wrappers instead of the worker functions.
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 23d7f30..232f9ea 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -95,8 +95,9 @@ EXPORT_SYMBOL(__blkdev_issue_discard);
* Description:
* Issue a discard request for the sectors in question.
*/
-int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
- sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
+static int do_blkdev_issue_discard(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, unsigned long flags,
+ bool ignore_nosupport)
{
int type = REQ_WRITE | REQ_DISCARD;
struct bio *bio = NULL;
@@ -111,13 +112,20 @@ int blkdev_issue_discard(struct block_device *bdev,
sector_t sector,
&bio);
if (!ret && bio) {
ret = submit_bio_wait(type, bio);
- if (ret == -EOPNOTSUPP)
+ if (ignore_nosupport && ret == -EOPNOTSUPP)
ret = 0;
}
blk_finish_plug(&plug);
return ret;
}
+
+int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
+{
+ return do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask,
+ flags, true);
+}
I'd prefer to do the EOPNOTSUPP mapping for the ioctl here instead of in
the do_blkdev_issue_discard() function. Then you don't need the
ignore_nosupport flag.
EXPORT_SYMBOL(blkdev_issue_discard);
/**
@@ -131,9 +139,9 @@ EXPORT_SYMBOL(blkdev_issue_discard);
* Description:
* Issue a write same request for the sectors in question.
*/
-int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
+static int do_blkdev_issue_write_same(struct block_device *bdev, sector_t
sector,
sector_t nr_sects, gfp_t gfp_mask,
- struct page *page)
+ struct page *page, bool ignore_nosupport)
{
struct request_queue *q = bdev_get_queue(bdev);
unsigned int max_write_same_sectors;
@@ -167,7 +175,15 @@ int blkdev_issue_write_same(struct block_device *bdev,
sector_t sector,
if (bio)
ret = submit_bio_wait(REQ_WRITE | REQ_WRITE_SAME, bio);
- return ret != -EOPNOTSUPP ? ret : 0;
+ return (ret != -EOPNOTSUPP || !ignore_nosupport) ? ret : 0;
+}
+
+int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask,
+ struct page *page)
+{
+ return do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
+ page, true);
}
EXPORT_SYMBOL(blkdev_issue_write_same);
There should not be a "soft" fail for WRITE SAME, it's not a hint.
@@ -238,12 +254,13 @@ int blkdev_issue_zeroout(struct block_device *bdev,
sector_t sector,
struct request_queue *q = bdev_get_queue(bdev);
if (discard && blk_queue_discard(q) && q->limits.discard_zeroes_data &&
- blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0) == 0)
+ do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0,
+ false) == 0)
return 0;
if (bdev_write_same(bdev) &&
- blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
- ZERO_PAGE(0)) == 0)
+ do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
+ ZERO_PAGE(0), false) == 0)
return 0;
return __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask);
--
Martin K. Petersen Oracle Linux Engineering
