[PATCH 3.14 52/53] tmpfs: fix regression hang in fallocate undo

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 3.14 52/53] tmpfs: fix regression hang in fallocate undo
Date	2016-07-25 23:20 +0200
Message-ID	<rYVs5-1c6-3@gated-at.bofh.it> (permalink)
References	<rYV8K-Pn-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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

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

From: Hugh Dickins <hughd@google.com>

commit 7f556567036cb7f89aabe2f0954b08566b4efb53 upstream.

The well-spotted fallocate undo fix is good in most cases, but not when
fallocate failed on the very first page.  index 0 then passes lend -1
to shmem_undo_range(), and that has two bad effects: (a) that it will
undo every fallocation throughout the file, unrestricted by the current
range; but more importantly (b) it can cause the undo to hang, because
lend -1 is treated as truncation, which makes it keep on retrying until
every page has gone, but those already fully instantiated will never go
away.  Big thank you to xfstests generic/269 which demonstrates this.

Fixes: b9b4bb26af01 ("tmpfs: don't undo fallocate past its last page")
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/shmem.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1893,9 +1893,11 @@ static long shmem_fallocate(struct file
 									NULL);
 		if (error) {
 			/* Remove the !PageUptodate pages we added */
-			shmem_undo_range(inode,
-				(loff_t)start << PAGE_CACHE_SHIFT,
-				((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
+			if (index > start) {
+				shmem_undo_range(inode,
+				 (loff_t)start << PAGE_CACHE_SHIFT,
+				 ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
+			}
 			goto undone;
 		}

Thread

[PATCH 3.14 00/53] 3.14.74-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 25/53] signal: remove warning about using SI_TKILL in rt_[tg]sigqueueinfo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 16/53] kprobes/x86: Clear TF bit in fault on single-stepping Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 40/53] iio: accel: kxsd9: fix the usage of spi_w8r8() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 39/53] staging: iio: accel: fix error check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 24/53] nfsd: check permissions when setting ACLs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 03/53] ipmr/ip6mr: Initialize the last assert time of mfc entries. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 05/53] usb: quirks: Add no-lpm quirk for Acer C120 LED Projector Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 17/53] x86/amd_nb: Fix boot crash on non-AMD systems Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 48/53] scsi: fix race between simultaneous decrements of ->host_failed Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:00 +0200
  [PATCH 3.14 49/53] Fix reconnect to not defer smb3 session reconnect long after socket reconnect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:10 +0200
  [PATCH 3.14 47/53] ALSA: ctl: Stop notification after disconnection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:10 +0200
  [PATCH 3.14 36/53] perf/x86: Honor the architectural performance monitoring version Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 52/53] tmpfs: fix regression hang in fallocate undo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 43/53] iio:ad7266: Fix probe deferral for vref Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 15/53] x86, build: copy ldlinux.c32 to image.iso Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 50/53] xen/acpi: allow xen-acpi-processor driver to load on Xen 4.7 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 31/53] HID: hiddev: validate num_values for HIDIOCGUSAGES, HIDIOCSUSAGES commands Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 13/53] powerpc/tm: Always reclaim in start_thread() for exec() class syscalls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 41/53] iio:ad7266: Fix broken regulator error handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 46/53] ALSA: au88x0: Fix calculation in vortex_wtdma_bufshift() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 45/53] ALSA: dummy: Fix a use-after-free at closing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 11/53] powerpc/iommu: Remove the dependency on EEH struct in DDW mechanism Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 53/53] s390/seccomp: fix error return for filtered system calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 44/53] tty/vt/keyboard: fix OOB access in do_compute_shiftstate() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 12/53] powerpc/pseries: Fix PCI config address for DDW Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 32/53] tracing: Handle NULL formats in hold_module_trace_bprintk_format() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 14/53] USB: EHCI: declare hostpc register as zero-length array Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 37/53] perf/x86: Fix undefined shift on 32-bit kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 29/53] kvm: Fix irq route entries exceeding KVM_MAX_IRQ_ROUTES Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 34/53] drm/radeon: fix asic initialization for virtualized environments Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 51/53] tmpfs: dont undo fallocate past its last page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 30/53] HID: elo: kill not flush the work Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 23/53] posix_acl: Add set_posix_acl Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 42/53] iio:ad7266: Fix support for optional regulators Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-25 23:20 +0200
  [PATCH 3.14 04/53] net: alx: Work around the DMA RX overflow issue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 21/53] mm: Export migrate_page_move_mapping and migrate_page_copy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 22/53] UBIFS: Implement ->migratepage() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 20/53] ARM: 8578/1: mm: ensure pmd_present only checks the valid bit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 19/53] NFS: Fix another OPEN_DOWNGRADE bug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 01/53] crypto: ux500 - memmove the right size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 07/53] usb: musb: Ensure rx reinit occurs for shared_fifo endpoints Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 18/53] make nfs_atomic_open() call d_drop() on all ->open_context() errors. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 02/53] sit: correct IP protocol used in ipip6_err Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 10/53] IB/mlx4: Properly initialize GRH TClass and FlowLabel in AHs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 28/53] KEYS: potential uninitialized variable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 09/53] mac80211_hwsim: Add missing check for HWSIM_ATTR_SIGNAL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  [PATCH 3.14 06/53] usb: musb: Stop bulk endpoint while queue is rotated Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-26 00:50 +0200
  Re: [PATCH 3.14 00/53] 3.14.74-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-07-26 04:10 +0200
  Re: [PATCH 3.14 00/53] 3.14.74-stable review Guenter Roeck <linux@roeck-us.net> - 2016-07-26 16:00 +0200

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