From: Jia-Ju Bai <baijiaju1990@gmail.com>
To: clm@fb.com, josef@toxicpanda.com, dsterba@suse.com
Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH 4/4] fs: btrfs: fix a data race in btrfs_block_rsv_release()
Date: Sat, 9 May 2020 13:34:31 +0800 [thread overview]
Message-ID: <20200509053431.3860-1-baijiaju1990@gmail.com> (raw)
The functions btrfs_block_rsv_release() and
btrfs_update_delayed_refs_rsv() are concurrently executed at runtime in
the following call contexts:
Thread 1:
btrfs_file_write_iter()
btrfs_buffered_write()
btrfs_delalloc_release_extents()
btrfs_inode_rsv_release()
__btrfs_block_rsv_release()
Thread 2:
finish_ordered_fn()
btrfs_finish_ordered_io()
insert_reserved_file_extent()
__btrfs_drop_extents()
btrfs_free_extent()
btrfs_add_delayed_data_ref()
btrfs_update_delayed_refs_rsv()
In __btrfs_block_rsv_release():
else if (... && !delayed_rsv->full)
In btrfs_update_delayed_refs_rsv():
spin_lock(&delayed_rsv->lock);
delayed_rsv->size += num_bytes;
delayed_rsv->full = 0;
spin_unlock(&delayed_rsv->lock);
Thus a data race for delayed_rsv->full can occur.
This race was found and actually reproduced by our conccurency fuzzer.
To fix this race, the spinlock delayed_rsv->lock is used to
protect the access to delayed_rsv->full in btrfs_block_rsv_release().
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
fs/btrfs/block-rsv.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index 27efec8f7c5b..89c53a7137b4 100644
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -277,6 +277,11 @@ u64 btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
struct btrfs_block_rsv *target = NULL;
+ unsigned short full = 0;
+
+ spin_lock(&delayed_rsv->lock);
+ full = delayed_rsv->full;
+ spin_unlock(&delayed_rsv->lock);
/*
* If we are the delayed_rsv then push to the global rsv, otherwise dump
@@ -284,7 +289,7 @@ u64 btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
*/
if (block_rsv == delayed_rsv)
target = global_rsv;
- else if (block_rsv != global_rsv && !delayed_rsv->full)
+ else if (block_rsv != global_rsv && !full)
target = delayed_rsv;
if (target && block_rsv->space_info != target->space_info)
--
2.17.1
next reply other threads:[~2020-05-09 5:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-09 5:34 Jia-Ju Bai [this message]
2020-05-12 22:18 ` [PATCH 4/4] fs: btrfs: fix a data race in btrfs_block_rsv_release() David Sterba
2020-05-13 2:18 ` Jia-Ju Bai
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200509053431.3860-1-baijiaju1990@gmail.com \
--to=baijiaju1990@gmail.com \
--cc=clm@fb.com \
--cc=dsterba@suse.com \
--cc=josef@toxicpanda.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).