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acc8f8628c
Ever since 6.12-rc1, I've observed a pile of warnings from the kernel when running fstests with quotas enabled: WARNING: CPU: 1 PID: 458580 at mm/page_alloc.c:4221 __alloc_pages_noprof+0xc9c/0xf18 CPU: 1 UID: 0 PID: 458580 Comm: xfsaild/sda3 Tainted: G W 6.12.0-rc6-djwa #rc6 6ee3e0e531f6457e2d26aa008a3b65ff184b377c <snip> Call trace: __alloc_pages_noprof+0xc9c/0xf18 alloc_pages_mpol_noprof+0x94/0x240 alloc_pages_noprof+0x68/0xf8 new_slab+0x3e0/0x568 ___slab_alloc+0x5a0/0xb88 __slab_alloc.constprop.0+0x7c/0xf8 __kmalloc_noprof+0x404/0x4d0 xfs_buf_get_map+0x594/0xde0 [xfs 384cb02810558b4c490343c164e9407332118f88] xfs_buf_read_map+0x64/0x2e0 [xfs 384cb02810558b4c490343c164e9407332118f88] xfs_trans_read_buf_map+0x1dc/0x518 [xfs 384cb02810558b4c490343c164e9407332118f88] xfs_qm_dqflush+0xac/0x468 [xfs 384cb02810558b4c490343c164e9407332118f88] xfs_qm_dquot_logitem_push+0xe4/0x148 [xfs 384cb02810558b4c490343c164e9407332118f88] xfsaild+0x3f4/0xde8 [xfs 384cb02810558b4c490343c164e9407332118f88] kthread+0x110/0x128 ret_from_fork+0x10/0x20 ---[ end trace 0000000000000000 ]--- This corresponds to the line: WARN_ON_ONCE(current->flags & PF_MEMALLOC); within the NOFAIL checks. What's happening here is that the XFS AIL is trying to write a disk quota update back into the filesystem, but for that it needs to read the ondisk buffer for the dquot. The buffer is not in memory anymore, probably because it was evicted. Regardless, the buffer cache tries to allocate a new buffer, but those allocations are NOFAIL. The AIL thread has marked itself PF_MEMALLOC (aka noreclaim) since commit43ff2122e6("xfs: on-stack delayed write buffer lists") presumably because reclaim can push on XFS to push on the AIL. An easy way to fix this probably would have been to drop the NOFAIL flag from the xfs_buf allocation and open code a retry loop, but then there's still the problem that for bs>ps filesystems, the buffer itself could require up to 64k worth of pages. Inode items had similar behavior (multi-page cluster buffers that we don't want to allocate in the AIL) which we solved by making transaction precommit attach the inode cluster buffers to the dirty log item. Let's solve the dquot problem in the same way. So: Make a real precommit handler to read the dquot buffer and attach it to the log item; pass it to dqflush in the push method; and have the iodone function detach the buffer once we've flushed everything. Add a state flag to the log item to track when a thread has entered the precommit -> push mechanism to skip the detaching if it turns out that the dquot is very busy, as we don't hold the dquot lock between log item commit and AIL push). Reading and attaching the dquot buffer in the precommit hook is inspired by the work done for inode cluster buffers some time ago. Cc: <stable@vger.kernel.org> # v6.12 Fixes:903edea6c5("mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner") Signed-off-by: "Darrick J. Wong" <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
29 lines
694 B
C
29 lines
694 B
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2000-2003 Silicon Graphics, Inc.
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* All Rights Reserved.
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*/
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#ifndef __XFS_DQUOT_ITEM_H__
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#define __XFS_DQUOT_ITEM_H__
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struct xfs_dquot;
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struct xfs_trans;
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struct xfs_mount;
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struct xfs_dq_logitem {
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struct xfs_log_item qli_item; /* common portion */
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struct xfs_dquot *qli_dquot; /* dquot ptr */
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xfs_lsn_t qli_flush_lsn; /* lsn at last flush */
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/*
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* We use this spinlock to coordinate access to the li_buf pointer in
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* the log item and the qli_dirty flag.
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*/
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spinlock_t qli_lock;
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bool qli_dirty; /* dirtied since last flush? */
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};
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void xfs_qm_dquot_logitem_init(struct xfs_dquot *dqp);
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#endif /* __XFS_DQUOT_ITEM_H__ */
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