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Date: Fri, 9 Oct 2020 17:02:44 +0800
From: Ye Bin <yebin10@...wei.com>
To: <tytso@....edu>, <adilger.kernel@...ger.ca>,
<linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: Ye Bin <yebin10@...wei.com>
Subject: [PATCH] ext4: Fix WARN_ON_ONCE in __ext4_handle_dirty_metadata()
When run fsstress with disk offline/online, I got follow warning:
[ 47.395783] ------------[ cut here ]------------
[ 47.400554] sd 1:0:0:0: rejecting I/O to offline device
[ 47.403327] WARNING: CPU: 3 PID: 2420 at fs/buffer.c:1117 mark_buffer_dirty+0xcd/0xe0
[ 47.406093] Modules linked in:
[ 47.407322] CPU: 3 PID: 2420 Comm: fsstress Not tainted 3.10.0-862.14.0.6.x86_64 #136
[ 47.409702] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),BIOS ?
-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc3104/01/2014
[ 47.413142] Call Trace:
[ 47.413473] sd 1:0:0:0: rejecting I/O to offline device
[ 47.414805] [<ffffffffa604697f>] dump_stack+0x19/0x1b
[ 47.415866] [<ffffffffa5895988>] __warn+0xd8/0x100
[ 47.416970] [<ffffffffa5895acd>] warn_slowpath_null+0x1d/0x20
[ 47.418115] [<ffffffffa5a5aecd>] mark_buffer_dirty+0xcd/0xe0
[ 47.419247] [<ffffffffa5af6a78>] __ext4_handle_dirty_metadata+0x1a8/0x220
[ 47.420408] [<ffffffffa5af65d3>] ? __ext4_journal_get_write_access+0x53/0x110
[ 47.421430] [<ffffffffa5abeec1>] __ext4_new_inode+0x921/0x1350
[ 47.422276] [<ffffffffa5ad22b9>] ext4_create+0xd9/0x1a0
[ 47.423071] [<ffffffffa5a31763>] vfs_create+0xd3/0x140
[ 47.423820] [<ffffffffa5a33870>] do_last+0x10f0/0x12c0
[ 47.424627] [<ffffffffa5bdc4fc>] ? selinux_file_alloc_security+0x3c/0x60
[ 47.425571] [<ffffffffa5a35877>] path_openat+0xd7/0x640
[ 47.426389] [<ffffffffa605885b>] ? system_call_fastpath+0x22/0x27
[ 47.428099] [<ffffffffa5a1c444>] ? create_object+0x234/0x310
[ 47.428922] [<ffffffffa5a3727d>] do_filp_open+0x4d/0xb0
[ 47.429724] [<ffffffffa5a90b69>] ? files_cgroup_alloc_fd+0x39/0x60
[ 47.430623] [<ffffffffa5a44c35>] ? __alloc_fd+0xe5/0x180
[ 47.431361] [<ffffffffa5a234a7>] do_sys_open+0x137/0x240
[ 47.432275] [<ffffffffa6058795>] ? system_call_after_swapgs+0xa2/0x146
[ 47.433214] [<ffffffffa5a235ce>] SyS_open+0x1e/0x20
[ 47.433959] [<ffffffffa5a23606>] SyS_creat+0x16/0x20
[ 47.434675] [<ffffffffa605885b>] system_call_fastpath+0x22/0x27
[ 47.435555] [<ffffffffa60587a1>] ? system_call_after_swapgs+0xae/0x146
[ 47.436468] ---[ end trace f8ed64a9adfa868b ]---
In fact, I got a lot of call trace. All call trace trigger warning when call
__ext4_handle_dirty_metadate.
If there are racing calls to __ext4_handle_dirty_metadate. It's possible for
another writeback result in the buffer being marked with an error after we check
if the buffer is marked as having a write error and the buffer up-to-date flag
is cleared. If that happens mark_buffer_dirty() can end up throwing a WARN_ON_ONCE.
To Fix this warning, lock buffer when call mark_buffer_dirty in function
__ext4_handle_dirty_metadate.
Signed-off-by: Ye Bin <yebin10@...wei.com>
---
fs/ext4/ext4_jbd2.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 760b9ee49dc0..306ede92ee40 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -355,11 +355,13 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
err);
}
} else {
+ lock_buffer(bh);
set_buffer_uptodate(bh);
if (inode)
mark_buffer_dirty_inode(bh, inode);
else
mark_buffer_dirty(bh);
+ unlock_buffer(bh);
if (inode && inode_needs_sync(inode)) {
sync_dirty_buffer(bh);
if (buffer_req(bh) && !buffer_uptodate(bh)) {
--
2.16.2.dirty
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