[PATCH AUTOSEL 5.4 076/330] xfs: fix log reservation overflows when allocating large rt extents

Sasha Levin
2020-09-18T03:10:04Z

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