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[PATCH 4.4 41/53] xfs: fix off-by-one on max nr_pages in xfs_find_get_desired_pgoff()

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

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

From: Eryu Guan <eguan@redhat.com>

commit 8affebe16d79ebefb1d9d6d56a46dc89716f9453 upstream.

xfs_find_get_desired_pgoff() is used to search for offset of hole or
data in page range [index, end] (both inclusive), and the max number
of pages to search should be at least one, if end == index.
Otherwise the only page is missed and no hole or data is found,
which is not correct.

When block size is smaller than page size, this can be demonstrated
by preallocating a file with size smaller than page size and writing
data to the last block. E.g. run this xfs_io command on a 1k block
size XFS on x86_64 host.

  # xfs_io -fc "falloc 0 3k" -c "pwrite 2k 1k" \
  	    -c "seek -d 0" /mnt/xfs/testfile
  wrote 1024/1024 bytes at offset 2048
  1 KiB, 1 ops; 0.0000 sec (33.675 MiB/sec and 34482.7586 ops/sec)
  Whence  Result
  DATA    EOF

Data at offset 2k was missed, and lseek(2) returned ENXIO.

This is uncovered by generic/285 subtest 07 and 08 on ppc64 host,
where pagesize is 64k. Because a recent change to generic/285
reduced the preallocated file size to smaller than 64k.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
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/xfs_file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1208,7 +1208,7 @@ xfs_find_get_desired_pgoff(
 		unsigned	nr_pages;
 		unsigned int	i;
 
-		want = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
+		want = min_t(pgoff_t, end - index, PAGEVEC_SIZE - 1) + 1;
 		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
 					  want);
 		/*

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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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