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Message-ID: <44b385ca-f00d-0b47-e370-bd7d97cb1be3@gmail.com>
Date: Sat, 27 Nov 2021 16:23:37 +0800
From: Jia-Ju Bai <baijiaju1990@...il.com>
To: clm@...com, josef@...icpanda.com, dsterba@...e.com
Cc: linux-btrfs@...r.kernel.org,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: [BUG] fs: btrfs: several possible ABBA deadlocks
Hello,
My static analysis tool reports several possible ABBA deadlocks in the
btrfs module in Linux 5.10:
# DEADLOCK 1:
__clear_extent_bit()
spin_lock(&tree->lock); --> Line 733 (Lock A)
split_state()
btrfs_split_delalloc_extent()
spin_lock(&BTRFS_I(inode)->lock); --> Line 1870 (Lock B)
btrfs_inode_safe_disk_i_size_write()
spin_lock(&BTRFS_I(inode)->lock); --> Line 53 (Lock B)
find_contiguous_extent_bit()
spin_lock(&tree->lock); --> Line 1620 (Lock A)
When __clear_extent_bit() and btrfs_inode_safe_disk_i_size_write() are
concurrently executed, the deadlock can occur.
# DEADLOCK 2:
__set_extent_bit()
spin_lock(&tree->lock); --> Line 995 (Lock A)
set_state_bits()
btrfs_set_delalloc_extent()
spin_lock(&BTRFS_I(inode)->lock); --> Line 2007 or 2017 or 2029
(Lock B)
btrfs_inode_safe_disk_i_size_write()
spin_lock(&BTRFS_I(inode)->lock); --> Line 53 (Lock B)
find_contiguous_extent_bit()
spin_lock(&tree->lock); --> Line 1620 (Lock A)
When __set_extent_bit() and btrfs_inode_safe_disk_i_size_write() are
concurrently executed, the deadlock can occur.
# DEADLOCK 3:
convert_extent_bit()
spin_lock(&tree->lock); --> Line 1241 (Lock A)
set_state_bits()
btrfs_set_delalloc_extent()
spin_lock(&BTRFS_I(inode)->lock); --> Line 2007 or 2017 or 2029
(Lock B)
btrfs_inode_safe_disk_i_size_write()
spin_lock(&BTRFS_I(inode)->lock); --> Line 53 (Lock B)
find_contiguous_extent_bit()
spin_lock(&tree->lock); --> Line 1620 (Lock A)
When convert_extent_bit() and btrfs_inode_safe_disk_i_size_write() are
concurrently executed, the deadlock can occur.
I am not quite sure whether these possible deadlocks are real and how to
fix them if they are real.
Any feedback would be appreciated, thanks :)
Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
Best wishes,
Jia-Ju Bai
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