f2fs: avoid to issue redundant discard commands

BugLink: http://bugs.launchpad.net/bugs/1672544
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>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 0d880245375890058602437d3c709bfedd3945b8..983bf0caf2df100de9325c238ae7168284fb13a8 100644 (file)
--- 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);