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Groups > linux.kernel > #1657987

[PATCH 4.4 40/53] xfs: Fix missed holes in SEEK_HOLE implementation

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.4 40/53] xfs: Fix missed holes in SEEK_HOLE implementation
Date 2017-06-05 19:20 +0200
Message-ID <tP3PC-5Lk-67@gated-at.bofh.it> (permalink)
References <tP33b-5dS-15@gated-at.bofh.it>
Organization linux.* mail to news gateway

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

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

From: Jan Kara <jack@suse.cz>

commit 5375023ae1266553a7baa0845e82917d8803f48c upstream.

XFS SEEK_HOLE implementation could miss a hole in an unwritten extent as
can be seen by the following command:

xfs_io -c "falloc 0 256k" -c "pwrite 0 56k" -c "pwrite 128k 8k"
       -c "seek -h 0" file
wrote 57344/57344 bytes at offset 0
56 KiB, 14 ops; 0.0000 sec (49.312 MiB/sec and 12623.9856 ops/sec)
wrote 8192/8192 bytes at offset 131072
8 KiB, 2 ops; 0.0000 sec (70.383 MiB/sec and 18018.0180 ops/sec)
Whence	Result
HOLE	139264

Where we can see that hole at offset 56k was just ignored by SEEK_HOLE
implementation. The bug is in xfs_find_get_desired_pgoff() which does
not properly detect the case when pages are not contiguous.

Fix the problem by properly detecting when found page has larger offset
than expected.

Fixes: d126d43f631f996daeee5006714fed914be32368
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-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/xfs_file.c |   29 +++++++++--------------------
 1 file changed, 9 insertions(+), 20 deletions(-)

--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1235,17 +1235,6 @@ xfs_find_get_desired_pgoff(
 			break;
 		}
 
-		/*
-		 * At lease we found one page.  If this is the first time we
-		 * step into the loop, and if the first page index offset is
-		 * greater than the given search offset, a hole was found.
-		 */
-		if (type == HOLE_OFF && lastoff == startoff &&
-		    lastoff < page_offset(pvec.pages[0])) {
-			found = true;
-			break;
-		}
-
 		for (i = 0; i < nr_pages; i++) {
 			struct page	*page = pvec.pages[i];
 			loff_t		b_offset;
@@ -1257,18 +1246,18 @@ xfs_find_get_desired_pgoff(
 			 * file mapping. However, page->index will not change
 			 * because we have a reference on the page.
 			 *
-			 * Searching done if the page index is out of range.
-			 * If the current offset is not reaches the end of
-			 * the specified search range, there should be a hole
-			 * between them.
+			 * If current page offset is beyond where we've ended,
+			 * we've found a hole.
 			 */
-			if (page->index > end) {
-				if (type == HOLE_OFF && lastoff < endoff) {
-					*offset = lastoff;
-					found = true;
-				}
+			if (type == HOLE_OFF && lastoff < endoff &&
+			    lastoff < page_offset(pvec.pages[i])) {
+				found = true;
+				*offset = lastoff;
 				goto out;
 			}
+			/* Searching done if the page index is out of range. */
+			if (page->index > end)
+				goto out;
 
 			lock_page(page);
 			/*

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Thread

[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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