From 348a1983cf4cf5099fc398438a968443af4c9f65 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 13 Jun 2024 08:51:48 +1000 Subject: xfs: fix unlink vs cluster buffer instantiation race Luis has been reporting an assert failure when freeing an inode cluster during inode inactivation for a while. The assert looks like: XFS: Assertion failed: bp->b_flags & XBF_DONE, file: fs/xfs/xfs_trans_buf.c, line: 241 ------------[ cut here ]------------ kernel BUG at fs/xfs/xfs_message.c:102! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 4 PID: 73 Comm: kworker/4:1 Not tainted 6.10.0-rc1 #4 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: xfs-inodegc/loop5 xfs_inodegc_worker [xfs] RIP: 0010:assfail (fs/xfs/xfs_message.c:102) xfs RSP: 0018:ffff88810188f7f0 EFLAGS: 00010202 RAX: 0000000000000000 RBX: ffff88816e748250 RCX: 1ffffffff844b0e7 RDX: 0000000000000004 RSI: ffff88810188f558 RDI: ffffffffc2431fa0 RBP: 1ffff11020311f01 R08: 0000000042431f9f R09: ffffed1020311e9b R10: ffff88810188f4df R11: ffffffffac725d70 R12: ffff88817a3f4000 R13: ffff88812182f000 R14: ffff88810188f998 R15: ffffffffc2423f80 FS: 0000000000000000(0000) GS:ffff8881c8400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055fe9d0f109c CR3: 000000014426c002 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: xfs_trans_read_buf_map (fs/xfs/xfs_trans_buf.c:241 (discriminator 1)) xfs xfs_imap_to_bp (fs/xfs/xfs_trans.h:210 fs/xfs/libxfs/xfs_inode_buf.c:138) xfs xfs_inode_item_precommit (fs/xfs/xfs_inode_item.c:145) xfs xfs_trans_run_precommits (fs/xfs/xfs_trans.c:931) xfs __xfs_trans_commit (fs/xfs/xfs_trans.c:966) xfs xfs_inactive_ifree (fs/xfs/xfs_inode.c:1811) xfs xfs_inactive (fs/xfs/xfs_inode.c:2013) xfs xfs_inodegc_worker (fs/xfs/xfs_icache.c:1841 fs/xfs/xfs_icache.c:1886) xfs process_one_work (kernel/workqueue.c:3231) worker_thread (kernel/workqueue.c:3306 (discriminator 2) kernel/workqueue.c:3393 (discriminator 2)) kthread (kernel/kthread.c:389) ret_from_fork (arch/x86/kernel/process.c:147) ret_from_fork_asm (arch/x86/entry/entry_64.S:257) And occurs when the the inode precommit handlers is attempt to look up the inode cluster buffer to attach the inode for writeback. The trail of logic that I can reconstruct is as follows. 1. the inode is clean when inodegc runs, so it is not attached to a cluster buffer when precommit runs. 2. #1 implies the inode cluster buffer may be clean and not pinned by dirty inodes when inodegc runs. 3. #2 implies that the inode cluster buffer can be reclaimed by memory pressure at any time. 4. The assert failure implies that the cluster buffer was attached to the transaction, but not marked done. It had been accessed earlier in the transaction, but not marked done. 5. #4 implies the cluster buffer has been invalidated (i.e. marked stale). 6. #5 implies that the inode cluster buffer was instantiated uninitialised in the transaction in xfs_ifree_cluster(), which only instantiates the buffers to invalidate them and never marks them as done. Given factors 1-3, this issue is highly dependent on timing and environmental factors. Hence the issue can be very difficult to reproduce in some situations, but highly reliable in others. Luis has an environment where it can be reproduced easily by g/531 but, OTOH, I've reproduced it only once in ~2000 cycles of g/531. I think the fix is to have xfs_ifree_cluster() set the XBF_DONE flag on the cluster buffers, even though they may not be initialised. The reasons why I think this is safe are: 1. A buffer cache lookup hit on a XBF_STALE buffer will clear the XBF_DONE flag. Hence all future users of the buffer know they have to re-initialise the contents before use and mark it done themselves. 2. xfs_trans_binval() sets the XFS_BLI_STALE flag, which means the buffer remains locked until the journal commit completes and the buffer is unpinned. Hence once marked XBF_STALE/XFS_BLI_STALE by xfs_ifree_cluster(), the only context that can access the freed buffer is the currently running transaction. 3. #2 implies that future buffer lookups in the currently running transaction will hit the transaction match code and not the buffer cache. Hence XBF_STALE and XFS_BLI_STALE will not be cleared unless the transaction initialises and logs the buffer with valid contents again. At which point, the buffer will be marked marked XBF_DONE again, so having XBF_DONE already set on the stale buffer is a moot point. 4. #2 also implies that any concurrent access to that cluster buffer will block waiting on the buffer lock until the inode cluster has been fully freed and is no longer an active inode cluster buffer. 5. #4 + #1 means that any future user of the disk range of that buffer will always see the range of disk blocks covered by the cluster buffer as not done, and hence must initialise the contents themselves. 6. Setting XBF_DONE in xfs_ifree_cluster() then means the unlinked inode precommit code will see a XBF_DONE buffer from the transaction match as it expects. It can then attach the stale but newly dirtied inode to the stale but newly dirtied cluster buffer without unexpected failures. The stale buffer will then sail through the journal and do the right thing with the attached stale inode during unpin. Hence the fix is just one line of extra code. The explanation of why we have to set XBF_DONE in xfs_ifree_cluster, OTOH, is long and complex.... Fixes: 82842fee6e59 ("xfs: fix AGF vs inode cluster buffer deadlock") Signed-off-by: Dave Chinner Tested-by: Luis Chamberlain Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Chandan Babu R --- fs/xfs/xfs_inode.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'fs/xfs/xfs_inode.c') diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 58fb7a5062e1..f36091e1e7f5 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -2548,11 +2548,26 @@ xfs_ifree_cluster( * This buffer may not have been correctly initialised as we * didn't read it from disk. That's not important because we are * only using to mark the buffer as stale in the log, and to - * attach stale cached inodes on it. That means it will never be - * dispatched for IO. If it is, we want to know about it, and we - * want it to fail. We can acheive this by adding a write - * verifier to the buffer. + * attach stale cached inodes on it. + * + * For the inode that triggered the cluster freeing, this + * attachment may occur in xfs_inode_item_precommit() after we + * have marked this buffer stale. If this buffer was not in + * memory before xfs_ifree_cluster() started, it will not be + * marked XBF_DONE and this will cause problems later in + * xfs_inode_item_precommit() when we trip over a (stale, !done) + * buffer to attached to the transaction. + * + * Hence we have to mark the buffer as XFS_DONE here. This is + * safe because we are also marking the buffer as XBF_STALE and + * XFS_BLI_STALE. That means it will never be dispatched for + * IO and it won't be unlocked until the cluster freeing has + * been committed to the journal and the buffer unpinned. If it + * is written, we want to know about it, and we want it to + * fail. We can acheive this by adding a write verifier to the + * buffer. */ + bp->b_flags |= XBF_DONE; bp->b_ops = &xfs_inode_buf_ops; /* -- cgit v1.2.3 From 610b29161b0aa9feb59b78dc867553274f17fb01 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 19 Jun 2024 10:32:43 -0700 Subject: xfs: fix freeing speculative preallocations for preallocated files xfs_can_free_eofblocks returns false for files that have persistent preallocations unless the force flag is passed and there are delayed blocks. This means it won't free delalloc reservations for files with persistent preallocations unless the force flag is set, and it will also free the persistent preallocations if the force flag is set and the file happens to have delayed allocations. Both of these are bad, so do away with the force flag and always free only post-EOF delayed allocations for files with the XFS_DIFLAG_PREALLOC or APPEND flags set. Signed-off-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Chandan Babu R --- fs/xfs/xfs_bmap_util.c | 30 ++++++++++++++++++++++-------- fs/xfs/xfs_bmap_util.h | 2 +- fs/xfs/xfs_icache.c | 2 +- fs/xfs/xfs_inode.c | 14 ++++---------- 4 files changed, 28 insertions(+), 20 deletions(-) (limited to 'fs/xfs/xfs_inode.c') diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index ac2e77ebb54c..a4d9fbc21b83 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -486,13 +486,11 @@ out_unlock: /* * Test whether it is appropriate to check an inode for and free post EOF - * blocks. The 'force' parameter determines whether we should also consider - * regular files that are marked preallocated or append-only. + * blocks. */ bool xfs_can_free_eofblocks( - struct xfs_inode *ip, - bool force) + struct xfs_inode *ip) { struct xfs_bmbt_irec imap; struct xfs_mount *mp = ip->i_mount; @@ -526,11 +524,11 @@ xfs_can_free_eofblocks( return false; /* - * Do not free real preallocated or append-only files unless the file - * has delalloc blocks and we are forced to remove them. + * Only free real extents for inodes with persistent preallocations or + * the append-only flag. */ if (ip->i_diflags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) - if (!force || ip->i_delayed_blks == 0) + if (ip->i_delayed_blks == 0) return false; /* @@ -584,6 +582,22 @@ xfs_free_eofblocks( /* Wait on dio to ensure i_size has settled. */ inode_dio_wait(VFS_I(ip)); + /* + * For preallocated files only free delayed allocations. + * + * Note that this means we also leave speculative preallocations in + * place for preallocated files. + */ + if (ip->i_diflags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) { + if (ip->i_delayed_blks) { + xfs_bmap_punch_delalloc_range(ip, + round_up(XFS_ISIZE(ip), mp->m_sb.sb_blocksize), + LLONG_MAX); + } + xfs_inode_clear_eofblocks_tag(ip); + return 0; + } + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp); if (error) { ASSERT(xfs_is_shutdown(mp)); @@ -891,7 +905,7 @@ xfs_prepare_shift( * Trim eofblocks to avoid shifting uninitialized post-eof preallocation * into the accessible region of the file. */ - if (xfs_can_free_eofblocks(ip, true)) { + if (xfs_can_free_eofblocks(ip)) { error = xfs_free_eofblocks(ip); if (error) return error; diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h index 51f84d8ff372..eb0895bfb9da 100644 --- a/fs/xfs/xfs_bmap_util.h +++ b/fs/xfs/xfs_bmap_util.h @@ -63,7 +63,7 @@ int xfs_insert_file_space(struct xfs_inode *, xfs_off_t offset, xfs_off_t len); /* EOF block manipulation functions */ -bool xfs_can_free_eofblocks(struct xfs_inode *ip, bool force); +bool xfs_can_free_eofblocks(struct xfs_inode *ip); int xfs_free_eofblocks(struct xfs_inode *ip); int xfs_swap_extents(struct xfs_inode *ip, struct xfs_inode *tip, diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c index 0953163a2d84..9967334ea99f 100644 --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -1155,7 +1155,7 @@ xfs_inode_free_eofblocks( } *lockflags |= XFS_IOLOCK_EXCL; - if (xfs_can_free_eofblocks(ip, false)) + if (xfs_can_free_eofblocks(ip)) return xfs_free_eofblocks(ip); /* inode could be preallocated or append-only */ diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index f36091e1e7f5..38f946e3be2d 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1595,7 +1595,7 @@ xfs_release( if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) return 0; - if (xfs_can_free_eofblocks(ip, false)) { + if (xfs_can_free_eofblocks(ip)) { /* * Check if the inode is being opened, written and closed * frequently and we have delayed allocation blocks outstanding @@ -1856,15 +1856,13 @@ xfs_inode_needs_inactive( /* * This file isn't being freed, so check if there are post-eof blocks - * to free. @force is true because we are evicting an inode from the - * cache. Post-eof blocks must be freed, lest we end up with broken - * free space accounting. + * to free. * * Note: don't bother with iolock here since lockdep complains about * acquiring it in reclaim context. We have the only reference to the * inode at this point anyways. */ - return xfs_can_free_eofblocks(ip, true); + return xfs_can_free_eofblocks(ip); } /* @@ -1947,15 +1945,11 @@ xfs_inactive( if (VFS_I(ip)->i_nlink != 0) { /* - * force is true because we are evicting an inode from the - * cache. Post-eof blocks must be freed, lest we end up with - * broken free space accounting. - * * Note: don't bother with iolock here since lockdep complains * about acquiring it in reclaim context. We have the only * reference to the inode at this point anyways. */ - if (xfs_can_free_eofblocks(ip, true)) + if (xfs_can_free_eofblocks(ip)) error = xfs_free_eofblocks(ip); goto out; -- cgit v1.2.3 From 673cd885bbbfd873aa6983ce2363a813b7826425 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 19 Jun 2024 10:32:46 -0700 Subject: xfs: honor init_xattrs in xfs_init_new_inode for !ATTR fs xfs_init_new_inode ignores the init_xattrs parameter for filesystems that do not have ATTR enabled. As a result, the first init_xattrs file to be created by the kernel will not have an attr fork created to store acls. Storing that first acl will add ATTR to the superblock flags, so subsequent files will be created with attr forks. The overhead of this is so small that chances are that nobody has noticed this behavior. However, this is disastrous on a filesystem with parent pointers because it requires that a new linkable file /must/ have a pre-existing attr fork, and the parent pointers code uses init_xattrs to create that fork. The preproduction version of mkfs.xfs used to set this, but the V5 sb verifier only requires ATTR2, not ATTR. There is no guard for filesystems with (PARENT && !ATTR). It turns out that I misunderstood the two flags -- ATTR means that we at some point created an attr fork to store xattrs in a file; ATTR2 apparently means only that inodes have dynamic fork offsets or that the filesystem was mounted with the "attr2" option. Fixes: 2442ee15bb1e ("xfs: eager inode attr fork init needs attr feature awareness") Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Signed-off-by: Chandan Babu R --- fs/xfs/xfs_inode.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'fs/xfs/xfs_inode.c') diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 38f946e3be2d..a4e3cd8971fc 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -42,6 +42,7 @@ #include "xfs_pnfs.h" #include "xfs_parent.h" #include "xfs_xattr.h" +#include "xfs_sb.h" struct kmem_cache *xfs_inode_cache; @@ -870,9 +871,16 @@ xfs_init_new_inode( * this saves us from needing to run a separate transaction to set the * fork offset in the immediate future. */ - if (init_xattrs && xfs_has_attr(mp)) { + if (init_xattrs) { ip->i_forkoff = xfs_default_attroffset(ip) >> 3; xfs_ifork_init_attr(ip, XFS_DINODE_FMT_EXTENTS, 0); + + if (!xfs_has_attr(mp)) { + spin_lock(&mp->m_sb_lock); + xfs_add_attr(mp); + spin_unlock(&mp->m_sb_lock); + xfs_log_sb(tp); + } } /* -- cgit v1.2.3