Patch "f2fs: avoid to issue redundant discard commands" has been added to the 4.9-stable tree

Patch "f2fs: avoid to issue redundant discard commands" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    f2fs: avoid to issue redundant discard commands

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     f2fs-avoid-to-issue-redundant-discard-commands.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8b107f5b97772c7c0c218302e9a4d15b4edf50b4 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Mon, 27 Feb 2017 11:57:11 -0800
Subject: f2fs: avoid to issue redundant discard commands

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
@@ -813,6 +813,8 @@ next:
 		start = start_segno + sbi->segs_per_sec;
 		if (start < end)
 			goto next;
+		else
+			end = start - 1;
 	}
 	mutex_unlock(&dirty_i->seglist_lock);
 


Patches currently in stable-queue which might be from jaegeuk@kernel.org are

queue-4.9/f2fs-add-ovp-valid_blocks-check-for-bg-gc-victim-to-fg_gc.patch
queue-4.9/f2fs-avoid-to-issue-redundant-discard-commands.patch
queue-4.9/f2fs-fix-multiple-f2fs_add_link-calls-having-same-name.patch
queue-4.9/f2fs-fix-a-problem-of-using-memory-after-free.patch