[PATCH] hfsplus: remove mutex_lock check in hfsplus_free_extents

[Yangtao Li <frank.li@vivo.com>]

Syzbot reported an issue in hfsplus subsystem:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 4400 at fs/hfsplus/extents.c:346
	hfsplus_free_extents+0x700/0xad0
Call Trace:
<TASK>
hfsplus_file_truncate+0x768/0xbb0 fs/hfsplus/extents.c:606
hfsplus_write_begin+0xc2/0xd0 fs/hfsplus/inode.c:56
cont_expand_zero fs/buffer.c:2383 [inline]
cont_write_begin+0x2cf/0x860 fs/buffer.c:2446
hfsplus_write_begin+0x86/0xd0 fs/hfsplus/inode.c:52
generic_cont_expand_simple+0x151/0x250 fs/buffer.c:2347
hfsplus_setattr+0x168/0x280 fs/hfsplus/inode.c:263
notify_change+0xe38/0x10f0 fs/attr.c:420
do_truncate+0x1fb/0x2e0 fs/open.c:65
do_sys_ftruncate+0x2eb/0x380 fs/open.c:193
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

To avoid deadlock, Commit 31651c607151 ("hfsplus: avoid deadlock
on file truncation") unlock extree before hfsplus_free_extents(),
and add check wheather extree is locked in hfsplus_free_extents().

However, when operations such as hfsplus_file_release,
hfsplus_setattr, hfsplus_unlink, and hfsplus_unlink are executed
concurrently in different files, it is very likely to trigger the
WARN_ON, which will lead syzbot and xfstest to consider it as an
abnormality.

Since we already have alloc_mutex to protect alloc file modify,
let's remove mutex_lock check.

Fixes: 31651c607151f ("hfsplus: avoid deadlock on file truncation")
Reported-by: syzbot+8c0bc9f818702ff75b76@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/00000000000057fa4605ef101c4c@google.com/
Signed-off-by: Yangtao Li <frank.li@vivo.com>
---
 fs/hfsplus/extents.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index a6d61685ae79..b1699b3c246a 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -342,9 +342,6 @@ static int hfsplus_free_extents(struct super_block *sb,
 	int i;
 	int err = 0;
 
-	/* Mapping the allocation file may lock the extent tree */
-	WARN_ON(mutex_is_locked(&HFSPLUS_SB(sb)->ext_tree->tree_lock));
-
 	hfsplus_dump_extent(extent);
 	for (i = 0; i < 8; extent++, i++) {
 		count = be32_to_cpu(extent->block_count);
-- 
2.48.1