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    Subject[PATCH AUTOSEL 5.4 076/330] xfs: fix log reservation overflows when allocating large rt extents
    Date
    From: "Darrick J. Wong" <darrick.wong@oracle.com>

    [ Upstream commit b1de6fc7520fe12949c070af0e8c0e4044cd3420 ]

    Omar Sandoval reported that a 4G fallocate on the realtime device causes
    filesystem shutdowns due to a log reservation overflow that happens when
    we log the rtbitmap updates. Factor rtbitmap/rtsummary updates into the
    the tr_write and tr_itruncate log reservation calculation.

    "The following reproducer results in a transaction log overrun warning
    for me:

    mkfs.xfs -f -r rtdev=/dev/vdc -d rtinherit=1 -m reflink=0 /dev/vdb
    mount -o rtdev=/dev/vdc /dev/vdb /mnt
    fallocate -l 4G /mnt/foo

    Reported-by: Omar Sandoval <osandov@osandov.com>
    Tested-by: Omar Sandoval <osandov@osandov.com>
    Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
    Reviewed-by: Brian Foster <bfoster@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/xfs/libxfs/xfs_trans_resv.c | 96 +++++++++++++++++++++++++++-------
    1 file changed, 77 insertions(+), 19 deletions(-)

    diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
    index d12bbd526e7c0..b3584cd2cc164 100644
    --- a/fs/xfs/libxfs/xfs_trans_resv.c
    +++ b/fs/xfs/libxfs/xfs_trans_resv.c
    @@ -196,6 +196,24 @@ xfs_calc_inode_chunk_res(
    return res;
    }

    +/*
    + * Per-extent log reservation for the btree changes involved in freeing or
    + * allocating a realtime extent. We have to be able to log as many rtbitmap
    + * blocks as needed to mark inuse MAXEXTLEN blocks' worth of realtime extents,
    + * as well as the realtime summary block.
    + */
    +unsigned int
    +xfs_rtalloc_log_count(
    + struct xfs_mount *mp,
    + unsigned int num_ops)
    +{
    + unsigned int blksz = XFS_FSB_TO_B(mp, 1);
    + unsigned int rtbmp_bytes;
    +
    + rtbmp_bytes = (MAXEXTLEN / mp->m_sb.sb_rextsize) / NBBY;
    + return (howmany(rtbmp_bytes, blksz) + 1) * num_ops;
    +}
    +
    /*
    * Various log reservation values.
    *
    @@ -218,13 +236,21 @@ xfs_calc_inode_chunk_res(

    /*
    * In a write transaction we can allocate a maximum of 2
    - * extents. This gives:
    + * extents. This gives (t1):
    * the inode getting the new extents: inode size
    * the inode's bmap btree: max depth * block size
    * the agfs of the ags from which the extents are allocated: 2 * sector
    * the superblock free block counter: sector size
    * the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
    - * And the bmap_finish transaction can free bmap blocks in a join:
    + * Or, if we're writing to a realtime file (t2):
    + * the inode getting the new extents: inode size
    + * the inode's bmap btree: max depth * block size
    + * the agfs of the ags from which the extents are allocated: 2 * sector
    + * the superblock free block counter: sector size
    + * the realtime bitmap: ((MAXEXTLEN / rtextsize) / NBBY) bytes
    + * the realtime summary: 1 block
    + * the allocation btrees: 2 trees * (2 * max depth - 1) * block size
    + * And the bmap_finish transaction can free bmap blocks in a join (t3):
    * the agfs of the ags containing the blocks: 2 * sector size
    * the agfls of the ags containing the blocks: 2 * sector size
    * the super block free block counter: sector size
    @@ -234,40 +260,72 @@ STATIC uint
    xfs_calc_write_reservation(
    struct xfs_mount *mp)
    {
    - return XFS_DQUOT_LOGRES(mp) +
    - max((xfs_calc_inode_res(mp, 1) +
    + unsigned int t1, t2, t3;
    + unsigned int blksz = XFS_FSB_TO_B(mp, 1);
    +
    + t1 = xfs_calc_inode_res(mp, 1) +
    + xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK), blksz) +
    + xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
    + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
    +
    + if (xfs_sb_version_hasrealtime(&mp->m_sb)) {
    + t2 = xfs_calc_inode_res(mp, 1) +
    xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK),
    - XFS_FSB_TO_B(mp, 1)) +
    + blksz) +
    xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
    - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2),
    - XFS_FSB_TO_B(mp, 1))),
    - (xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
    - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2),
    - XFS_FSB_TO_B(mp, 1))));
    + xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 1), blksz) +
    + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1), blksz);
    + } else {
    + t2 = 0;
    + }
    +
    + t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
    + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
    +
    + return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
    }

    /*
    - * In truncating a file we free up to two extents at once. We can modify:
    + * In truncating a file we free up to two extents at once. We can modify (t1):
    * the inode being truncated: inode size
    * the inode's bmap btree: (max depth + 1) * block size
    - * And the bmap_finish transaction can free the blocks and bmap blocks:
    + * And the bmap_finish transaction can free the blocks and bmap blocks (t2):
    * the agf for each of the ags: 4 * sector size
    * the agfl for each of the ags: 4 * sector size
    * the super block to reflect the freed blocks: sector size
    * worst case split in allocation btrees per extent assuming 4 extents:
    * 4 exts * 2 trees * (2 * max depth - 1) * block size
    + * Or, if it's a realtime file (t3):
    + * the agf for each of the ags: 2 * sector size
    + * the agfl for each of the ags: 2 * sector size
    + * the super block to reflect the freed blocks: sector size
    + * the realtime bitmap: 2 exts * ((MAXEXTLEN / rtextsize) / NBBY) bytes
    + * the realtime summary: 2 exts * 1 block
    + * worst case split in allocation btrees per extent assuming 2 extents:
    + * 2 exts * 2 trees * (2 * max depth - 1) * block size
    */
    STATIC uint
    xfs_calc_itruncate_reservation(
    struct xfs_mount *mp)
    {
    - return XFS_DQUOT_LOGRES(mp) +
    - max((xfs_calc_inode_res(mp, 1) +
    - xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1,
    - XFS_FSB_TO_B(mp, 1))),
    - (xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) +
    - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4),
    - XFS_FSB_TO_B(mp, 1))));
    + unsigned int t1, t2, t3;
    + unsigned int blksz = XFS_FSB_TO_B(mp, 1);
    +
    + t1 = xfs_calc_inode_res(mp, 1) +
    + xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1, blksz);
    +
    + t2 = xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) +
    + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4), blksz);
    +
    + if (xfs_sb_version_hasrealtime(&mp->m_sb)) {
    + t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
    + xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 2), blksz) +
    + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
    + } else {
    + t3 = 0;
    + }
    +
    + return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
    }

    /*
    --
    2.25.1
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