linux-kernel - Re: [PATCH v2] f2fs: avoid deadlock in f2fs_shrink_extent

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151201014622.GA51854@jaegeuk.local>
Date:	Mon, 30 Nov 2015 17:46:22 -0800
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v2] f2fs: avoid deadlock in f2fs_shrink_extent_tree

Change log from v1:
 o fix bug

>From 8cd63b5e91daeeccc1f158425c74de0f462c96af Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@...nel.org>
Date: Mon, 30 Nov 2015 16:26:44 -0800
Subject: [PATCH] f2fs: avoid deadlock in f2fs_shrink_extent_tree

While handling extent trees, we can enter into a reclaiming path anytime.
If it tries to release some extent nodes in the same extent tree,
write_lock(&et->lock) would be hanged.
In order to avoid the deadlock, we can just skip it.

Note that, if it is an unreferenced tree, we should get write_lock(&et->lock)
successfully and release all of therein nodes.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/extent_cache.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 7ddba81..de063f2 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -615,9 +615,10 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 		for (i = 0; i < found; i++) {
 			struct extent_tree *et = treevec[i];
 
-			write_lock(&et->lock);
-			node_cnt += __free_extent_tree(sbi, et, false);
-			write_unlock(&et->lock);
+			if (write_trylock(&et->lock)) {
+				node_cnt += __free_extent_tree(sbi, et, false);
+				write_unlock(&et->lock);
+			}
 
 			if (node_cnt + tree_cnt >= nr_shrink)
 				goto unlock_out;
-- 
2.4.9 (Apple Git-60)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/