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Subject[PATCH 4.10 147/167] f2fs: avoid to issue redundant discard commands
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jaegeuk Kim <jaegeuk@kernel.org>

commit 8b107f5b97772c7c0c218302e9a4d15b4edf50b4 upstream.

If segs_per_sec is over 1 like under SMR, previously f2fs issues discard
commands redundantly on the same section, since we didn't move end position
for the previous discard command.

E.g.,

start end
| |
prefree_bitmap = [01111100111100]

And, after issue discard for this section,
end start
| |
prefree_bitmap = [01111100111100]

Select this section again by searching from (end + 1),
start end
| |
prefree_bitmap = [01111100111100]

Fixes: 36abef4e796d38 ("f2fs: introduce mode=lfs mount option")
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/f2fs/segment.c | 2 ++
1 file changed, 2 insertions(+)

--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -935,6 +935,8 @@ next:
start = start_segno + sbi->segs_per_sec;
if (start < end)
goto next;
+ else
+ end = start - 1;
}
mutex_unlock(&dirty_i->seglist_lock);


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