From: "Darrick J. Wong" <djwong@kernel.org>
To: Morduan Zang <zhangdandan@uniontech.com>
Cc: cem@kernel.org, zhanjun@uniontech.com, hch@lst.de,
dchinner@redhat.com, stable@vger.kernel.org,
linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+d78ace33ad4ee69329d5@syzkaller.appspotmail.com
Subject: Re: [PATCH] xfs: use GFP_NOFS in __xfs_trans_alloc
Date: Thu, 12 Mar 2026 07:26:01 -0700 [thread overview]
Message-ID: <20260312142601.GI1770774@frogsfrogsfrogs> (raw)
In-Reply-To: <24B50BB66059E3C8+20260312072214.475115-1-zhangdandan@uniontech.com>
On Thu, Mar 12, 2026 at 03:22:14PM +0800, Morduan Zang wrote:
> __xfs_trans_alloc() allocates the transaction structure before
> xfs_trans_set_context() establishes the nofs context. If memory reclaim
> enters XFS through xfs_vn_sync_lazytime(), this GFP_KERNEL allocation can
> trigger a warning from the reclaim path.
>
> Use GFP_NOFS for the transaction allocation to avoid filesystem reclaim
> recursion before the nofs context is set.
Why doesn't filesystem reclaim itself set PF_MEMALLOC_NOFS for us?
xfs_vn_sync_lazytime+0xaf/0x150 fs/xfs/xfs_iops.c:1238
sync_lazytime+0x12d/0x2d0 fs/fs-writeback.c:1721
iput+0x230/0xe80 fs/inode.c:1997
__dentry_kill+0x1a2/0x5e0 fs/dcache.c:670
shrink_kill+0xa9/0x2c0 fs/dcache.c:1147
shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1174
prune_dcache_sb+0x119/0x180 fs/dcache.c:1256
super_cache_scan+0x369/0x4b0 fs/super.c:223
do_shrink_slab+0x6df/0x1170 mm/shrinker.c:437`
--D
> Link: https://syzkaller.appspot.com/bug?extid=d78ace33ad4ee69329d5
> Fixes: 83a80e95e797 ("xfs: decouple xfs_trans_alloc_empty from xfs_trans_alloc")
> Reported-by: syzbot+d78ace33ad4ee69329d5@syzkaller.appspotmail.com
>
> Signed-off-by: Zhan Jun <zhanjun@uniontech.com>
> Signed-off-by: Morduan Zang <zhangdandan@uniontech.com>
> ---
> fs/xfs/xfs_trans.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index bcc470f56e46..0d347cff7317 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -217,7 +217,7 @@ __xfs_trans_alloc(
>
> ASSERT(!(flags & XFS_TRANS_RES_FDBLKS) || xfs_has_lazysbcount(mp));
>
> - tp = kmem_cache_zalloc(xfs_trans_cache, GFP_KERNEL | __GFP_NOFAIL);
> + tp = kmem_cache_zalloc(xfs_trans_cache, GFP_NOFS | __GFP_NOFAIL);
> if (!(flags & XFS_TRANS_NO_WRITECOUNT))
> sb_start_intwrite(mp->m_super);
> xfs_trans_set_context(tp);
> --
> 2.50.1
>
>
next prev parent reply other threads:[~2026-03-12 14:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-12 7:22 [PATCH] xfs: use GFP_NOFS in __xfs_trans_alloc Morduan Zang
2026-03-12 14:26 ` Darrick J. Wong [this message]
2026-03-12 20:28 ` Dave Chinner
2026-03-12 20:25 ` Dave Chinner
2026-03-16 9:18 ` Christoph Hellwig
2026-03-18 21:01 ` Dave Chinner
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