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Commits on Apr 12, 2021
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xfs: set aside allocation btree blocks from block reservation
The blocks used for allocation btrees (bnobt and countbt) are technically considered free space. This is because as free space is used, allocbt blocks are removed and naturally become available for traditional allocation. However, this means that a significant portion of free space may consist of in-use btree blocks if free space is severely fragmented. On large filesystems with large perag reservations, this can lead to a rare but nasty condition where a significant amount of physical free space is available, but the majority of actual usable blocks consist of in-use allocbt blocks. We have a record of a (~12TB, 32 AG) filesystem with multiple AGs in a state with ~2.5GB or so free blocks tracked across ~300 total allocbt blocks, but effectively at 100% full because the the free space is entirely consumed by refcountbt perag reservation. Such a large perag reservation is by design on large filesystems. The problem is that because the free space is so fragmented, this AG contributes the 300 or so allocbt blocks to the global counters as free space. If this pattern repeats across enough AGs, the filesystem lands in a state where global block reservation can outrun physical block availability. For example, a streaming buffered write on the affected filesystem continues to allow delayed allocation beyond the point where writeback starts to fail due to physical block allocation failures. The expected behavior is for the delalloc block reservation to fail gracefully with -ENOSPC before physical block allocation failure is a possibility. To address this problem, introduce an in-core counter to track the sum of all allocbt blocks in use by the filesystem. Use the new counter to set these blocks aside at reservation time and thus ensure they cannot be reserved until truly available. Since this is only necessary when perag reservations are active and the counter requires a read of each AGF to fully populate, only enforce on perag res enabled filesystems. This allows initialization of the counter at ->pagf_init time because the perag reservation init code reads each AGF at mount time. Signed-off-by: Brian Foster <bfoster@redhat.com>
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xfs: set a mount flag when perag reservation is active
perag reservation is enabled at mount time on a per AG basis. The upcoming in-core allocation btree accounting mechanism needs to know when reservation is enabled and that all perag AGF contexts are initialized. As a preparation step, set a flag in the mount structure and unconditionally initialize the pagf on all mounts where at least one reservation is active. Signed-off-by: Brian Foster <bfoster@redhat.com>
Commits on Apr 9, 2021
Commits on Apr 7, 2021
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xfs: scrub: Disable check for unoptimized data fork bmbt node
xchk_btree_check_minrecs() checks if the contents of the immediate child of a bmbt root block can fit within the root block. This check could fail on inodes with an attr fork since xfs_bmap_add_attrfork_btree() used to demote the current root node of the data fork as the child of a newly allocated root node if it found that the size of "struct xfs_btree_block" along with the space required for records exceeded that of space available in the data fork. xfs_bmap_add_attrfork_btree() should have used "struct xfs_bmdr_block" instead of "struct xfs_btree_block" for the above mentioned space requirement calculation. This commit disables the check for unoptimized (in terms of disk space usage) data fork bmbt trees since there could be filesystems in use that already have such a layout. Suggested-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
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xfs: Use struct xfs_bmdr_block instead of struct xfs_btree_block to c…
…alculate root node size The incore data fork of an inode stores the bmap btree root node as 'struct xfs_btree_block'. However, the ondisk version of the inode stores the bmap btree root node as a 'struct xfs_bmdr_block'. xfs_bmap_add_attrfork_btree() checks if the btree root node fits inside the data fork of the inode. However, it incorrectly uses 'struct xfs_btree_block' to compute the size of the bmap btree root node. Since size of 'struct xfs_btree_block' is larger than that of 'struct xfs_bmdr_block', xfs_bmap_add_attrfork_btree() could end up unnecessarily demoting the current root node as the child of newly allocated root node. This commit optimizes space usage by modifying xfs_bmap_add_attrfork_btree() to use 'struct xfs_bmdr_block' to check if the bmap btree root node fits inside the data fork of the inode. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
