From: Brian Foster bfoster@redhat.com

commit 7cd3099f4925d7c15887d1940ebd65acd66100f5 upstream.

Per-inode ioend completion batching has a log reservation deadlock vector between preallocated append transactions and transactions that are acquired at completion time for other purposes (i.e., unwritten extent conversion or COW fork remaps). For example, if the ioend completion workqueue task executes on a batch of ioends that are sorted such that an append ioend sits at the tail, it's possible for the outstanding append transaction reservation to block allocation of transactions required to process preceding ioends in the list.

Append ioend completion is historically the common path for on-disk inode size updates. While file extending writes may have completed sometime earlier, the on-disk inode size is only updated after successful writeback completion. These transactions are preallocated serially from writeback context to mitigate concurrency and associated log reservation pressure across completions processed by multi-threaded workqueue tasks.

However, now that delalloc blocks unconditionally map to unwritten extents at physical block allocation time, size updates via append ioends are relatively rare. This means that inode size updates most commonly occur as part of the preexisting completion time transaction to convert unwritten extents. As a result, there is no longer a strong need to preallocate size update transactions.

Remove the preallocation of inode size update transactions to avoid the ioend completion processing log reservation deadlock. Instead, continue to send all potential size extending ioends to workqueue context for completion and allocate the transaction from that context. This ensures that no outstanding log reservation is owned by the ioend completion worker task when it begins to process ioends.

Signed-off-by: Brian Foster bfoster@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Darrick J. Wong djwong@kernel.org Reported-by: Christian Theune ct@flyingcircus.io Link: https://lore.kernel.org/linux-xfs/CAOQ4uxjj2UqA0h4Y31NbmpHksMhVrXfXjLG4Tnz3z... Signed-off-by: Amir Goldstein amir73il@gmail.com Acked-by: Darrick J. Wong djwong@kernel.org ---

Greg,

One more fix from v5.13 that I missed from my backports.

Thanks, Amir.

fs/xfs/xfs_aops.c | 45 +++------------------------------------------ 1 file changed, 3 insertions(+), 42 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 953de843d9c3..e341d6531e68 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -39,33 +39,6 @@ static inline bool xfs_ioend_is_append(struct iomap_ioend *ioend) XFS_I(ioend->io_inode)->i_d.di_size; }

-STATIC int -xfs_setfilesize_trans_alloc( - struct iomap_ioend *ioend) -{ - struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount; - struct xfs_trans *tp; - int error; - - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp); - if (error) - return error; - - ioend->io_private = tp; - - /* - * We may pass freeze protection with a transaction. So tell lockdep - * we released it. - */ - __sb_writers_release(ioend->io_inode->i_sb, SB_FREEZE_FS); - /* - * We hand off the transaction to the completion thread now, so - * clear the flag here. - */ - xfs_trans_clear_context(tp); - return 0; -} - /* * Update on-disk file size now that data has been written to disk. */ @@ -191,12 +164,10 @@ xfs_end_ioend( error = xfs_reflink_end_cow(ip, offset, size); else if (ioend->io_type == IOMAP_UNWRITTEN) error = xfs_iomap_write_unwritten(ip, offset, size, false); - else - ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_private);

+ if (!error && xfs_ioend_is_append(ioend)) + error = xfs_setfilesize(ip, ioend->io_offset, ioend->io_size); done: - if (ioend->io_private) - error = xfs_setfilesize_ioend(ioend, error); iomap_finish_ioends(ioend, error); memalloc_nofs_restore(nofs_flag); } @@ -246,7 +217,7 @@ xfs_end_io(

static inline bool xfs_ioend_needs_workqueue(struct iomap_ioend *ioend) { - return ioend->io_private || + return xfs_ioend_is_append(ioend) || ioend->io_type == IOMAP_UNWRITTEN || (ioend->io_flags & IOMAP_F_SHARED); } @@ -259,8 +230,6 @@ xfs_end_bio( struct xfs_inode *ip = XFS_I(ioend->io_inode); unsigned long flags;

- ASSERT(xfs_ioend_needs_workqueue(ioend)); - spin_lock_irqsave(&ip->i_ioend_lock, flags); if (list_empty(&ip->i_ioend_list)) WARN_ON_ONCE(!queue_work(ip->i_mount->m_unwritten_workqueue, @@ -510,14 +479,6 @@ xfs_prepare_ioend( ioend->io_offset, ioend->io_size); }

- /* Reserve log space if we might write beyond the on-disk inode size. */ - if (!status && - ((ioend->io_flags & IOMAP_F_SHARED) || - ioend->io_type != IOMAP_UNWRITTEN) && - xfs_ioend_is_append(ioend) && - !ioend->io_private) - status = xfs_setfilesize_trans_alloc(ioend); - memalloc_nofs_restore(nofs_flag);

if (xfs_ioend_needs_workqueue(ioend))