Patch "xfs: reserve enough blocks to handle btree splits when remapping" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

xfs: reserve enough blocks to handle btree splits when remapping

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xfs-reserve-enough-blocks-to-handle-btree-splits-when-remapping.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Darrick J. Wong" <[email protected]>
Date: Wed, 12 Apr 2017 12:26:07 -0700
Subject: xfs: reserve enough blocks to handle btree splits when remapping

From: Darrick J. Wong <[email protected]>

commit fe0be23e68200573de027de9b8cc2b27e7fce35e upstream.

In xfs_reflink_end_cow, we erroneously reserve only enough blocks to handle adding 1 extent. This is problematic if we fragment free space, have to do CoW, and then have to perform multiple bmap btree expansions. Furthermore, the BUI recovery routine doesn't reserve /any/ blocks to handle btree splits, so log recovery fails after our first error causes the filesystem to go down.

Therefore, refactor the transaction block reservation macros until we have a macro that works for our deferred (re)mapping activities, and fix both problems by using that macro.

With 1k blocks we can hit this fairly often in g/187 if the scratch fs is big enough.

---
 fs/xfs/libxfs/xfs_trans_space.h |   23 +++++++++++++++++------
 fs/xfs/xfs_bmap_item.c          |    5 ++++-
 fs/xfs/xfs_reflink.c            |   18 ++++++++++++++++--
 3 files changed, 37 insertions(+), 9 deletions(-)

@@ -21,8 +21,20 @@
 /*
  * Components of space reservations.
  */
+
+/* Worst case number of rmaps that can be held in a block. */
 #define XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp)    \
 		(((mp)->m_rmap_mxr[0]) - ((mp)->m_rmap_mnr[0]))
+
+/* Adding one rmap could split every level up to the top of the tree. */
+#define XFS_RMAPADD_SPACE_RES(mp) ((mp)->m_rmap_maxlevels)
+
+/* Blocks we might need to add "b" rmaps to a tree. */
+#define XFS_NRMAPADD_SPACE_RES(mp, b)\
+	(((b + XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) - 1) / \
+	  XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp)) * \
+	  XFS_RMAPADD_SPACE_RES(mp))
+
 #define XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp)    \
 		(((mp)->m_alloc_mxr[0]) - ((mp)->m_alloc_mnr[0]))
 #define	XFS_EXTENTADD_SPACE_RES(mp,w)	(XFS_BM_MAXLEVELS(mp,w) - 1)

@@ -30,13 +42,12 @@
 	(((b + XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp) - 1) / \
 	  XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp)) * \
 	  XFS_EXTENTADD_SPACE_RES(mp,w))
+
+/* Blocks we might need to add "b" mappings & rmappings to a file. */
 #define XFS_SWAP_RMAP_SPACE_RES(mp,b,w)\
-	(((b + XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp) - 1) / \
-	  XFS_MAX_CONTIG_EXTENTS_PER_BLOCK(mp)) * \
-	  XFS_EXTENTADD_SPACE_RES(mp,w) + \
-	 ((b + XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp) - 1) / \
-	  XFS_MAX_CONTIG_RMAPS_PER_BLOCK(mp)) * \
-	  (mp)->m_rmap_maxlevels)
+	(XFS_NEXTENTADD_SPACE_RES((mp), (b), (w)) + \
+	 XFS_NRMAPADD_SPACE_RES((mp), (b)))
+
 #define	XFS_DAENTER_1B(mp,w)	\
 	((w) == XFS_DATA_FORK ? (mp)->m_dir_geo->fsbcount : 1)
 #define	XFS_DAENTER_DBS(mp,w)	\

@@ -34,6 +34,8 @@
 #include "xfs_bmap.h"
 #include "xfs_icache.h"
 #include "xfs_trace.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_trans_space.h"
 
 
 kmem_zone_t	*xfs_bui_zone;

@@ -446,7 +448,8 @@ xfs_bui_recover(
 		return -EIO;
 	}
 
-	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate,
+			XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK), 0, 0, &tp);
 	if (error)
 		return error;
 	budp = xfs_trans_get_bud(tp, buip);

@@ -736,8 +736,22 @@ xfs_reflink_end_cow(
 	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 	end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 
-	/* Start a rolling transaction to switch the mappings */
-	resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
+	/*
+	 * Start a rolling transaction to switch the mappings.  We're
+	 * unlikely ever to have to remap 16T worth of single-block
+	 * extents, so just cap the worst case extent count to 2^32-1.
+	 * Stick a warning in just in case, and avoid 64-bit division.
+	 */
+	BUILD_BUG_ON(MAX_RW_COUNT > UINT_MAX);
+	if (end_fsb - offset_fsb > UINT_MAX) {
+		error = -EFSCORRUPTED;
+		xfs_force_shutdown(ip->i_mount, SHUTDOWN_CORRUPT_INCORE);
+		ASSERT(0);
+		goto out;
+	}
+	resblks = XFS_NEXTENTADD_SPACE_RES(ip->i_mount,
+			(unsigned int)(end_fsb - offset_fsb),
+			XFS_DATA_FORK);
 	error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
 			resblks, 0, 0, &tp);
 	if (error)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/xfs-fix-missed-holes-in-seek_hole-implementation.patch queue-4.9/xfs-fix-indlen-accounting-error-on-partial-delalloc-conversion.patch queue-4.9/xfs-fix-over-copying-of-getbmap-parameters-from-userspace.patch queue-4.9/xfs-bad-assertion-for-delalloc-an-extent-that-start-at-i_size.patch queue-4.9/xfs-bmapx-shouldn-t-barf-on-inline-format-directories.patch queue-4.9/xfs-drop-iolock-from-reclaim-context-to-appease-lockdep.patch queue-4.9/xfs-fix-off-by-one-on-max-nr_pages-in-xfs_find_get_desired_pgoff.patch queue-4.9/xfs-update-ag-iterator-to-support-wait-on-new-inodes.patch queue-4.9/xfs-use-dedicated-log-worker-wq-to-avoid-deadlock-with-cil-wq.patch queue-4.9/xfs-fix-up-quotacheck-buffer-list-error-handling.patch queue-4.9/xfs-wait-on-new-inodes-during-quotaoff-dquot-release.patch queue-4.9/xfs-rework-the-inline-directory-verifiers.patch queue-4.9/xfs-use-b_state-to-fix-buffer-i-o-accounting-release-race.patch queue-4.9/xfs-avoid-mount-time-deadlock-in-cow-extent-recovery.patch queue-4.9/xfs-fix-off-by-in-in-loop-termination-in-xfs_find_get_desired_pgoff.patch queue-4.9/xfs-xfs_trans_alloc_empty.patch queue-4.9/xfs-fix-integer-truncation-in-xfs_bmap_remap_alloc.patch queue-4.9/xfs-actually-report-xattr-extents-via-iomap.patch queue-4.9/xfs-fix-use-after-free-in-xfs_finish_page_writeback.patch queue-4.9/xfs-reserve-enough-blocks-to-handle-btree-splits-when-remapping.patch queue-4.9/xfs-support-ability-to-wait-on-new-inodes.patch queue-4.9/xfs-verify-inline-directory-data-forks.patch queue-4.9/xfs-prevent-multi-fsb-dir-readahead-from-reading-random-blocks.patch queue-4.9/xfs-fix-unaligned-access-in-xfs_btree_visit_blocks.patch queue-4.9/xfs-handle-array-index-overrun-in-xfs_dir2_leaf_readbuf.patch queue-4.9/xfs-fix-kernel-memory-exposure-problems.patch