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[PATCH 4.4 49/53] xfs: fix indlen accounting error on partial delalloc conversion

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Brian Foster <bfoster@redhat.com>

commit 0daaecacb83bc6b656a56393ab77a31c28139bc7 upstream.

The delalloc -> real block conversion path uses an incorrect
calculation in the case where the middle part of a delalloc extent
is being converted. This is documented as a rare situation because
XFS generally attempts to maximize contiguity by converting as much
of a delalloc extent as possible.

If this situation does occur, the indlen reservation for the two new
delalloc extents left behind by the conversion of the middle range
is calculated and compared with the original reservation. If more
blocks are required, the delta is allocated from the global block
pool. This delta value can be characterized as the difference
between the new total requirement (temp + temp2) and the currently
available reservation minus those blocks that have already been
allocated (startblockval(PREV.br_startblock) - allocated).

The problem is that the current code does not account for previously
allocated blocks correctly. It subtracts the current allocation
count from the (new - old) delta rather than the old indlen
reservation. This means that more indlen blocks than have been
allocated end up stashed in the remaining extents and free space
accounting is broken as a result.

Fix up the calculation to subtract the allocated block count from
the original extent indlen and thus correctly allocate the
reservation delta based on the difference between the new total
requirement and the unused blocks from the original reservation.
Also remove a bogus assert that contradicts the fact that the new
indlen reservation can be larger than the original indlen
reservation.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/xfs/libxfs/xfs_bmap.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -2179,8 +2179,10 @@ xfs_bmap_add_extent_delay_real(
 		}
 		temp = xfs_bmap_worst_indlen(bma->ip, temp);
 		temp2 = xfs_bmap_worst_indlen(bma->ip, temp2);
-		diff = (int)(temp + temp2 - startblockval(PREV.br_startblock) -
-			(bma->cur ? bma->cur->bc_private.b.allocated : 0));
+		diff = (int)(temp + temp2 -
+			     (startblockval(PREV.br_startblock) -
+			      (bma->cur ?
+			       bma->cur->bc_private.b.allocated : 0)));
 		if (diff > 0) {
 			error = xfs_mod_fdblocks(bma->ip->i_mount,
 						 -((int64_t)diff), false);
@@ -2232,7 +2234,6 @@ xfs_bmap_add_extent_delay_real(
 		temp = da_new;
 		if (bma->cur)
 			temp += bma->cur->bc_private.b.allocated;
-		ASSERT(temp <= da_old);
 		if (temp < da_old)
 			xfs_mod_fdblocks(bma->ip->i_mount,
 					(int64_t)(da_old - temp), false);

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[PATCH 4.4 00/53] 4.4.71-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 18:30 +0200
  [PATCH 4.4 37/53] mm/migrate: fix refcount handling when !hugepage_migration_supported() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:20 +0200
  [PATCH 4.4 44/53] xfs: prevent multi-fsb dir readahead from reading random blocks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:20 +0200
  [PATCH 4.4 40/53] xfs: Fix missed holes in SEEK_HOLE implementation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:20 +0200
  [PATCH 4.4 46/53] xfs: support ability to wait on new inodes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:20 +0200
  [PATCH 4.4 41/53] xfs: fix off-by-one on max nr_pages in xfs_find_get_desired_pgoff() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:20 +0200
  [PATCH 4.4 14/53] ipv6: Check ip6_find_1stfragopt() return value properly. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 51/53] xfs: fix unaligned access in xfs_btree_visit_blocks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 47/53] xfs: update ag iterator to support wait on new inodes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 28/53] mmc: sdhci-iproc: suppress spurious interrupt with Multiblock read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 11/53] tcp: eliminate negative reordering in tcp_clean_rtx_queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 50/53] xfs: bad assertion for delalloc an extent that start at i_size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 52/53] xfs: in _attrlist_by_handle, copy the cursor back to userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 34/53] ALSA: hda - apply STAC_9200_DELL_M22 quirk for Dell Latitude D430 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 29/53] HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 12/53] net: Improve handling of failures on link and route dumps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 27/53] i2c: i2c-tiny-usb: fix buffer not being DMA capable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 15/53] bridge: netlink: check vlan_default_pvid range Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 05/53] s390/qeth: unbreak OSM and OSN support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 20/53] virtio-net: enable TSO/checksum offloads for Q-in-Q vlans Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 49/53] xfs: fix indlen accounting error on partial delalloc conversion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 25/53] net: phy: marvell: Limit errata to 88m1101 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 03/53] ipv6/dccp: do not inherit ipv6_mc_list from parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 39/53] PCI/PM: Add needs_resume flag to avoid suspend complete optimization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
    Re: [PATCH 4.4 39/53] PCI/PM: Add needs_resume flag to avoid  suspend complete optimization Ben Hutchings <ben.hutchings@codethink.co.uk> - 2017-06-06 18:20 +0200
      Re: [PATCH 4.4 39/53] PCI/PM: Add needs_resume flag to avoid suspend  complete optimization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-07 11:50 +0200
  [PATCH 4.4 07/53] s390/qeth: add missing hash table initializations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
    Re: [PATCH 4.4 07/53] s390/qeth: add missing hash table  initializations Julian Wiedmann <jwi@linux.vnet.ibm.com> - 2017-06-06 10:20 +0200
      Re: [PATCH 4.4 07/53] s390/qeth: add missing hash table  initializations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-06 11:00 +0200
  [PATCH 4.4 04/53] s390/qeth: handle sysfs error during initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:30 +0200
  [PATCH 4.4 02/53] dccp/tcp: do not inherit mc_list from parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:40 +0200
  [PATCH 4.4 01/53] sparc: Fix -Wstringop-overflow warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:40 +0200
  Re: [PATCH 4.4 00/53] 4.4.71-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-05 22:40 +0200
  Re: [PATCH 4.4 00/53] 4.4.71-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-06 00:10 +0200
    Re: [PATCH 4.4 00/53] 4.4.71-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-06 09:30 +0200

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