Commit cfd73237 ("ext4: add prefetching for block allocation
bitmaps") introduced block bitmap prefetch, and expects to read block
bitmaps of flex_bg through an IO.  However, it seems to ignore the
value range of s_log_groups_per_flex.  In the scenario where the value
of s_log_groups_per_flex is greater than 27, s_mb_prefetch or
s_mb_prefetch_limit will overflow, cause a divide zero exception.

In addition, the logic of calculating nr is also flawed, because the
size of flexbg is fixed during a single mount, but s_mb_prefetch can
be modified, which causes nr to fail to meet the value condition of
[1, flexbg_size].

To solve this problem, we need to set the upper limit of
s_mb_prefetch.  Since we expect to load block bitmaps of a flex_bg
through an IO, we can consider determining a reasonable upper limit
among the IO limit parameters.  After consideration, we chose
BLK_MAX_SEGMENT_SIZE.  This is a good choice to solve divide zero
problem and avoiding performance degradation.

[ Some minor code simplifications to make the changes easy to follow -- TYT ]
Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Samuel Liao <samuelliao@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1607051143-24508-1-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

When filesystem inconsistency is detected with group locked, we
currently try to modify superblock to store error there without
blocking. However this can cause superblock checksum failures (or
DIF/DIX failure) when the superblock is just being written out.

Make error handling code just store error information in ext4_sb_info
structure and copy it to on-disk superblock only in ext4_commit_super().
In case of error happening with group locked, we just postpone the
superblock flushing to a workqueue.

[ Added fixup so that s_first_error_* does not get updated after
  the file system is remounted.
  Also added fix for syzbot failure.  - Ted ]
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201127113405.26867-8-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Hillf Danton <hdanton@sina.com>
Reported-by: syzbot+9043030c040ce1849a60@syzkaller.appspotmail.com

We convert errno's to ext4 on-disk format error codes in
save_error_info(). Add a function and a bit of macro magic to make this
simpler.
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-7-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Just move error info related functions in super.c close to
ext4_handle_error(). We'll want to combine save_error_info() with
ext4_handle_error() and this makes change more obvious and saves a
forward declaration as well. No functional change.
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-6-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

The only difference between __ext4_abort() and __ext4_error() is that
the former one ignores errors=continue mount option. Unify the code to
reduce duplication.
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-5-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

We use __ext4_error() when ext4_protect_reserved_inode() finds
filesystem corruption. However EXT4_ERROR_INODE_ERR() is perfectly
capable of reporting all the needed information. So just use that.
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-4-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Superblock is written out either through ext4_commit_super() or through
ext4_handle_dirty_super(). In both cases we recompute the checksum so it
is not necessary to recompute it after updating superblock free inodes &
blocks counters.
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-3-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

ext4_handle_error() with errors=continue mount option can accidentally
remount the filesystem read-only when the system is rebooting. Fix that.

Fixes: 1dc1097f ("ext4: avoid panic during forced reboot")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20201127113405.26867-2-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Xattr code using inodes with large xattr data can end up dropping last
inode reference (and thus deleting the inode) from places like
ext4_xattr_set_entry(). That function is called with transaction started
and so ext4_evict_inode() can deadlock against fs freezing like:

CPU1					CPU2

removexattr()				freeze_super()
  vfs_removexattr()
    ext4_xattr_set()
      handle = ext4_journal_start()
      ...
      ext4_xattr_set_entry()
        iput(old_ea_inode)
          ext4_evict_inode(old_ea_inode)
					  sb->s_writers.frozen = SB_FREEZE_FS;
					  sb_wait_write(sb, SB_FREEZE_FS);
					  ext4_freeze()
					    jbd2_journal_lock_updates()
					      -> blocks waiting for all
					         handles to stop
            sb_start_intwrite()
	      -> blocks as sb is already in SB_FREEZE_FS state

Generally it is advisable to delete inodes from a separate transaction
as it can consume quite some credits however in this case it would be
quite clumsy and furthermore the credits for inode deletion are quite
limited and already accounted for. So just tweak ext4_evict_inode() to
avoid freeze protection if we have transaction already started and thus
it is not really needed anyway.

Cc: stable@vger.kernel.org
Fixes: dec214d0 ("ext4: xattr inode deduplication")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127110649.24730-1-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Add a helper to read number of fast commit blocks from jbd2 superblock
and also rename the JBD2_MIN_FC_BLKS to
JBD2_DEFAULT_FAST_COMMIT_BLOCKS since this constant is just the
default number of fast commit blocks to use in case number of fast
commit blocks isn't set in jbd2 superblock.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201120202232.2240293-2-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

This patch makes fast_commit.h byte by byte identical with
e2fsprogs/fast_commit.h. This will help us ensure that there are no
on-disk format inconsistencies between e2fsck and kernel ext4.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201120202232.2240293-1-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a break statement instead of just letting the code
fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/03497331f088a938d7a728e7a689bd7953139429.1605896059.git.gustavoars@kernel.orgSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Fast commit on-disk format is designed such that the replay of these
tags can be idempotent. This patch adds documentation in the code in
form of comments and in form kernel docs that describes these
characteristics. This patch also adds a TODO item needed to ensure
kernel fast commit replay idempotence.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201119232822.1860882-1-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

There are no callers of the EXT4_CURRENT_REV macro, so remove it.
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1605164202-31120-1-git-send-email-kaixuxia@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

The ext4_find_extent() function never returns NULL, it returns error
pointers.

Fixes: 44059e503b03 ("ext4: fast commit recovery path")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201023112232.GB282278@mwandaSigned-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

Check for valid block size directly by validating s_log_block_size; we
were doing this in two places.  First, by calculating blocksize via
BLOCK_SIZE << s_log_block_size, and then checking that the blocksize
was valid.  And then secondly, by checking s_log_block_size directly.

The first check is not reliable, and can trigger an UBSAN warning if
s_log_block_size on a maliciously corrupted superblock is greater than
22.  This is harmless, since the second test will correctly reject the
maliciously fuzzed file system, but to make syzbot shut up, and
because the two checks are duplicative in any case, delete the
blocksize check, and move the s_log_block_size earlier in
ext4_fill_super().
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-by: syzbot+345b75652b1d24227443@syzkaller.appspotmail.com

When freeing metadata, we will create an ext4_free_data and
insert it into the pending free list.  After the current
transaction is committed, the object will be freed.

ext4_mb_free_metadata() will check whether the area to be freed
overlaps with the pending free list. If true, return directly. At this
time, ext4_free_data is leaked.  Fortunately, the probability of this
problem is small, since it only occurs if the file system is corrupted
such that a block is claimed by more one inode and those inodes are
deleted within a single jbd2 transaction.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Link: https://lore.kernel.org/r/1604764698-4269-8-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1604764698-4269-7-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Since ext4_data_block_valid() has been renamed to ext4_inode_block_valid(),
the related comments need to be updated.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1604764698-4269-5-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

The code of mb_find_order_for_block is a bit obscure, but we can
simplify it with mb_find_buddy(), make the code more concise.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1604764698-4269-3-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

After this patch (163a203d), if an abnormal bitmap is detected, we
will mark the group as corrupt, and we will not use this group in
the future. Therefore, it should be meaningless to regenerate the
buddy bitmap of this group, It might be better to delete it.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1604764698-4269-2-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

There are currently multiple forms of assertion, such as J_ASSERT().
J_ASEERT() is provided for the jbd module, which is a public module.
Maybe we should use custom ASSERT() like other file systems, such as
xfs, which would be better.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/1604764698-4269-1-git-send-email-brookxu@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

Right now, it is hard to understand which quota journalling type is enabled:
you need to be quite familiar with kernel code and trace it or really
understand what different combinations of fs flags/mount options lead to.

This patch adds printing of current quota jounalling mode on each
mount/remount, thus making it easier to check it at a glance/in autotests.
The semantics is similar to ext4 data journalling modes:

* journalled - quota configured, journalling will be enabled
* writeback  - quota configured, journalling won't be enabled
* none       - quota isn't configured
* disabled   - kernel compiled without CONFIG_QUOTA feature
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1603336860-16153-2-git-send-email-dotdot@yandex-team.ruSigned-off-by: Roman Anufriev <dotdot@yandex-team.ru>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Right now, there are several places, where we check whether fs is
capable of enabling quota or if quota is journalled with quite long
and non-self-descriptive condition statements.

This patch wraps these statements into helpers for better readability
and easier usage.

Link: https://lore.kernel.org/r/1603336860-16153-1-git-send-email-dotdot@yandex-team.ruReviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Roman Anufriev <dotdot@yandex-team.ru>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Variable ex is assigned a variable that is not being read, the assignment
is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20201021132326.148052-1-colin.king@canonical.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

bv_page can't be NULL in a valid bio_vec, so we can remove the NULL check,
as we did in other places when calling bio_for_each_segment_all() to go
through all bio_vec of a bio.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Xianting Tian <tian.xianting@h3c.com>
Link: https://lore.kernel.org/r/20201020082201.34257-1-tian.xianting@h3c.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

The out_fail branch path don't release the bh and the second bh is
valid only in the for statement, so we don't need to set them to NULL.
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/1603194069-17557-1-git-send-email-kaixuxia@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

We used LockDoc to derive locking rules for each member
of struct transaction_t.
Based on those results, we extended the existing documentation
by more members of struct transaction_t, and updated the existing
documentation.

Link: https://lore.kernel.org/r/10cfbef1-994c-c604-f8a6-b1042fcc622f@tu-dortmund.deSigned-off-by: Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
Signed-off-by: Horst Schirmeier <horst.schirmeier@tu-dortmund.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Pull HID fixes from Jiri Kosina:

 - Various functionality / regression fixes for Logitech devices from
   Hans de Goede

 - Fix for (recently added) GPIO support in mcp2221 driver from Lars
   Povlsen

 - Power management handling fix/quirk in i2c-hid driver for certain
   BIOSes that have strange aproach to power-cycle from Hans de Goede

 - a few device ID additions and device-specific quirks

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid:
  HID: logitech-dj: Fix Dinovo Mini when paired with a MX5x00 receiver
  HID: logitech-dj: Fix an error in mse_bluetooth_descriptor
  HID: Add Logitech Dinovo Edge battery quirk
  HID: logitech-hidpp: Add HIDPP_CONSUMER_VENDOR_KEYS quirk for the Dinovo Edge
  HID: logitech-dj: Handle quad/bluetooth keyboards with a builtin trackpad
  HID: add HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE for Gamevice devices
  HID: mcp2221: Fix GPIO output handling
  HID: hid-sensor-hub: Fix issue with devices with no report ID
  HID: i2c-hid: Put ACPI enumerated devices in D3 on shutdown
  HID: add support for Sega Saturn
  HID: cypress: Support Varmilo Keyboards' media hotkeys
  HID: ite: Replace ABS_MISC 120/121 events with touchpad on/off keypresses
  HID: logitech-hidpp: Add PID for MX Anywhere 2
  HID: uclogic: Add ID for Trust Flex Design Tablet

Pull scheduler fixes from Thomas Gleixner:
 "A couple of scheduler fixes:

   - Make the conditional update of the overutilized state work
     correctly by caching the relevant flags state before overwriting
     them and checking them afterwards.

   - Fix a data race in the wakeup path which caused loadavg on ARM64
     platforms to become a random number generator.

   - Fix the ordering of the iowaiter accounting operations so it can't
     be decremented before it is incremented.

   - Fix a bug in the deadline scheduler vs. priority inheritance when a
     non-deadline task A has inherited the parameters of a deadline task
     B and then blocks on a non-deadline task C.

     The second inheritance step used the static deadline parameters of
     task A, which are usually 0, instead of further propagating task
     B's parameters. The zero initialized parameters trigger a bug in
     the deadline scheduler"

* tag 'sched-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/deadline: Fix priority inheritance with multiple scheduling classes
  sched: Fix rq->nr_iowait ordering
  sched: Fix data-race in wakeup
  sched/fair: Fix overutilized update in enqueue_task_fair()

Pull perf fix from Thomas Gleixner:
 "A single fix for the x86 perf sysfs interfaces which used kobject
  attributes instead of device attributes and therefore making clang's
  control flow integrity checker upset"

* tag 'perf-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86: fix sysfs type mismatches

Pull locking fix from Thomas Gleixner:
 "A single fix for lockdep which makes the recursion protection cover
  graph lock/unlock"

* tag 'locking-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep: Put graph lock/unlock under lock_recursion protection

Pull EFI fixes from Borislav Petkov:
 "Forwarded EFI fixes from Ard Biesheuvel:

   - fix memory leak in efivarfs driver

   - fix HYP mode issue in 32-bit ARM version of the EFI stub when built
     in Thumb2 mode

   - avoid leaking EFI pgd pages on allocation failure"

* tag 'efi-urgent-for-v5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/x86: Free efi_pgd with free_pages()
  efivarfs: fix memory leak in efivarfs_create()
  efi/arm: set HSCTLR Thumb2 bit correctly for HVC calls from HYP

Pull x86 fixes from Borislav Petkov:

 - An IOMMU VT-d build fix when CONFIG_PCI_ATS=n along with a revert of
   same because the proper one is going through the IOMMU tree (Thomas
   Gleixner)

 - An Intel microcode loader fix to save the correct microcode patch to
   apply during resume (Chen Yu)

 - A fix to not access user memory of other processes when dumping
   opcode bytes (Thomas Gleixner)

* tag 'x86_urgent_for_v5.10-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "iommu/vt-d: Take CONFIG_PCI_ATS into account"
  x86/dumpstack: Do not try to access user space code of other tasks
  x86/microcode/intel: Check patch signature before saving microcode for early loading
  iommu/vt-d: Take CONFIG_PCI_ATS into account

Merge misc fixes from Andrew Morton:
 "8 patches.

  Subsystems affected by this patch series: mm (madvise, pagemap,
  readahead, memcg, userfaultfd), kbuild, and vfs"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: fix madvise WILLNEED performance problem
  libfs: fix error cast of negative value in simple_attr_write()
  mm/userfaultfd: do not access vma->vm_mm after calling handle_userfault()
  mm: memcg/slab: fix root memcg vmstats
  mm: fix readahead_page_batch for retry entries
  mm: fix phys_to_target_node() and memory_add_physaddr_to_nid() exports
  compiler-clang: remove version check for BPF Tracing
  mm/madvise: fix memory leak from process_madvise

Pull staging and IIO fixes from Greg KH:
 "Here are some small Staging and IIO driver fixes for 5.10-rc5. They
  include:

   - IIO fixes for reported regressions and problems

   - new device ids for IIO drivers

   - new device id for rtl8723bs driver

   - staging ralink driver Kconfig dependency fix

   - staging mt7621-pci bus resource fix

  All of these have been in linux-next all week with no reported issues"

* tag 'staging-5.10-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  iio: accel: kxcjk1013: Add support for KIOX010A ACPI DSM for setting tablet-mode
  iio: accel: kxcjk1013: Replace is_smo8500_device with an acpi_type enum
  docs: ABI: testing: iio: stm32: remove re-introduced unsupported ABI
  iio: light: fix kconfig dependency bug for VCNL4035
  iio/adc: ingenic: Fix AUX/VBAT readings when touchscreen is used
  iio/adc: ingenic: Fix battery VREF for JZ4770 SoC
  staging: rtl8723bs: Add 024c:0627 to the list of SDIO device-ids
  staging: ralink-gdma: fix kconfig dependency bug for DMA_RALINK
  staging: mt7621-pci: avoid to request pci bus resources
  iio: imu: st_lsm6dsx: set 10ms as min shub slave timeout
  counter/ti-eqep: Fix regmap max_register
  iio: adc: stm32-adc: fix a regression when using dma and irq
  iio: adc: mediatek: fix unset field
  iio: cros_ec: Use default frequencies when EC returns invalid information

Pull tty fixes from Greg KH:
 "Here are some small tty/serial fixes for 5.10-rc5 that resolve some
  reported issues:

   - speakup crash when telling the kernel to use a device that isn't
     really there

   - imx serial driver fixes for reported problems

   - ar933x_uart driver fix for probe error handling path

  All have been in linux-next for a while with no reported issues"

* tag 'tty-5.10-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial: ar933x_uart: disable clk on error handling path in probe
  tty: serial: imx: keep console clocks always on
  speakup: Do not let the line discipline be used several times
  tty: serial: imx: fix potential deadlock

Pull ext4 fixes from Ted Ts'o:
 "A final set of miscellaneous bug fixes for ext4"

* tag 'ext4_for_linus_fixes2' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: fix bogus warning in ext4_update_dx_flag()
  jbd2: fix kernel-doc markups
  ext4: drop fast_commit from /proc/mounts

When doing a lookup in a directory, the afs filesystem uses a bulk
status fetch to speculatively retrieve the statuses of up to 48 other
vnodes found in the same directory and it will then either update extant
inodes or create new ones - effectively doing 'lookup ahead'.

To avoid the possibility of deadlocking itself, however, the filesystem
doesn't lock all of those inodes; rather just the directory inode is
locked (by the VFS).

When the operation completes, afs_inode_init_from_status() or
afs_apply_status() is called, depending on whether the inode already
exists, to commit the new status.

A case exists, however, where the speculative status fetch operation may
straddle a modification operation on one of those vnodes.  What can then
happen is that the speculative bulk status RPC retrieves the old status,
and whilst that is happening, the modification happens - which returns
an updated status, then the modification status is committed, then we
attempt to commit the speculative status.

This results in something like the following being seen in dmesg:

	kAFS: vnode modified {100058:861} 8->9 YFS.InlineBulkStatus

showing that for vnode 861 on volume 100058, we saw YFS.InlineBulkStatus
say that the vnode had data version 8 when we'd already recorded version
9 due to a local modification.  This was causing the cache to be
invalidated for that vnode when it shouldn't have been.  If it happens
on a data file, this might lead to local changes being lost.

Fix this by ignoring speculative status updates if the data version
doesn't match the expected value.

Note that it is possible to get a DV regression if a volume gets
restored from a backup - but we should get a callback break in such a
case that should trigger a recheck anyway.  It might be worth checking
the volume creation time in the volsync info and, if a change is
observed in that (as would happen on a restore), invalidate all caches
associated with the volume.

Fixes: 5cf9dd55 ("afs: Prospectively look up extra files when doing a single lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>