Commit Graph

211356 Commits

Author SHA1 Message Date
Jeff Liu
2decd65a26 ocfs2: Avoid to evaluate xattr block flags again.
It was evaludated to indexed before, check it is ok i think.

Signed-off-by: Jeff Liu <jeff.liu@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-10-15 13:03:43 -07:00
Joel Becker
fc3718918f Merge branch 'globalheartbeat-2' of git://oss.oracle.com/git/smushran/linux-2.6 into ocfs2-merge-window
Conflicts:
	fs/ocfs2/ocfs2.h
2010-10-15 13:03:09 -07:00
Sunil Mushran
d4396eafe4 ocfs2/cluster: Release debugfs file elapsed_time_in_ms
An earlier commit forgot to remove a debugfs file, elapsed_time_in_ms.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-15 11:57:21 -07:00
Tristan Ye
7bdb0d18bf ocfs2: Add a mount option "coherency=*" to handle cluster coherency for O_DIRECT writes.
Currently, the default behavior of O_DIRECT writes was allowing
concurrent writing among nodes to the same file, with no cluster
coherency guaranteed (no EX lock held).  This can leave stale data in
the cache for buffered reads on other nodes.

The new mount option introduce a chance to choose two different
behaviors for O_DIRECT writes:

    * coherency=full, as the default value, will disallow
                      concurrent O_DIRECT writes by taking
                      EX locks.

    * coherency=buffered, allow concurrent O_DIRECT writes
                          without EX lock among nodes, which
                          gains high performance at risk of
                          getting stale data on other nodes.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-10-11 14:14:55 -07:00
Goldwyn Rodrigues
75d9bbc738 Initialize max_slots early
Functions such as ocfs2_recovery_init() make use of osb->max_slots.
Initialize osb->max_slots early so the functions may use the correct
value.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.de>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-10-11 13:56:32 -07:00
Poyo VL
f30d44f3e5 When I tried to compile I got the following warning:
fs/ocfs2/slot_map.c: In function ‘ocfs2_init_slot_info’:
fs/ocfs2/slot_map.c:360: warning: ‘bytes’ may be used uninitialized in this function
fs/ocfs2/slot_map.c:360: note: ‘bytes’ was declared here
Compiler: gcc version 4.4.3 (GCC) on Mandriva
I'm not sure why this warning occurs, I think compiler don't know that variable
"bytes" is initialized when it is sent by reference to
ocfs2_slot_map_physical_size and it throws that ugly warning.
However, a simple initialization of "bytes" variable with 0 will fix it.

Signed-off-by: Ionut Gabriel Popescu <poyo_vl@yahoo.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-10-11 13:45:52 -07:00
Srinivas Eeda
9b5cd10e4c ocfs2: validate bg_free_bits_count after update
This patch adds a safe check to ensure bg_free_bits_count doesn't exceed
bg_bits in a group descriptor. This is to avoid on disk corruption that was
seen recently.

debugfs: group <52803072>
       Group Chain: 179   Parent Inode: 11  Generation: 2959379682
       CRC32: 00000000   ECC: 0000
       ##   Block#            Total    Used     Free     Contig   Size
       0    52803072          32256    4294965350   34202    18207    4032
       ......

Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-10-11 13:43:24 -07:00
Sunil Mushran
4d94aa1b1d ocfs2/cluster: Bump up dlm protocol to version 1.1
dlm protocol 1.1. activates messages DLM_QUERY_REGION and DLM_QUERY_NODEINFO
that are a must for global heartbeat.

It also activates o2hb_global_heartbeat_active().

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-09 10:27:04 -07:00
Sunil Mushran
43695d095d ocfs2/cluster: Show per region heartbeat elapsed time
This patch adds a per region debugfs file that shows the elapsed time
since the time the o2hb timer was last armed.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:09 -07:00
Sunil Mushran
d6aa1c7c9e ocfs2/cluster: Add mlogs for heartbeat up/down events
This patch adds mlogs for o2hb up and down events.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 18:50:50 -07:00
Sunil Mushran
1f28530537 ocfs2/cluster: Create debugfs dir/files for each region
This patch creates debugfs directory for each o2hb region and creates
files to expose the region number and the per region live node bitmap.
This information will be useful in debugging cluster issues.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:12 -07:00
Sunil Mushran
a6de013654 ocfs2/cluster: Create debugfs files for live, quorum and failed region bitmaps
This patch prints the bitmaps of live, quorum and failed regions. This
information will be useful in debugging cluster issues.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:13 -07:00
Sunil Mushran
b1c5ebfbe3 ocfs2/cluster: Maintain bitmap of failed regions
In global heartbeat mode, we track the bitmap of regions that have seen
heartbeat timeouts. We fence if the number of such regions is greater than
or equal to half the number of quorum regions.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 17:05:52 -07:00
Sunil Mushran
43182d2a79 ocfs2/cluster: Maintain bitmap of quorum regions
o2hb allows online adding of regions. However, a newly added region is not
used in quorum calculations unless it has been added on all nodes. This patch
tracks a bitmap of such quorum regions.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:16 -07:00
Sunil Mushran
e7d656baf6 ocfs2/cluster: Track bitmap of live heartbeat regions
A heartbeat region becomes live (or active) after a fixed number of (steady)
iterations.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:18 -07:00
Sunil Mushran
536f0741f3 ocfs2/cluster: Track number of global heartbeat regions
In global heartbeat mode, we have a upper limit for the number of active regions.
This patch adds the facility to track the number of active global heartbeat
regions and fails to start heartbeat if the number exceeds the maximum.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 17:03:07 -07:00
Sunil Mushran
823a637ae9 ocfs2/cluster: Maintain live node bitmap per heartbeat region
Currently we track a global livenode bitmap that keeps track of all nodes
that are heartbeating in all regions.

This patch adds the ability to track the livenode bitmap on a per region basis.
We will use this facility in a later patch to allow us to withstand the loss of
a minority number of regions.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:21 -07:00
Sunil Mushran
8ca8b0bbd8 ocfs2/cluster: Reorganize o2hb debugfs init
o2hb debugfs handling is reorganized to allow for easy expansion.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 17:01:27 -07:00
Sunil Mushran
0e105d37c2 ocfs2/cluster: Check slots for unconfigured live nodes
o2hb currently checks slots for configured nodes only. This patch makes
it check the slots for the live nodes too to take care of a race in which
a node is removed from the configuration but not from the live map.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 17:00:16 -07:00
Sunil Mushran
39a298563e ocfs2/cluster: Print messages when adding/removing nodes
Prints messages when the user adds or removes nodes.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 17:30:17 -07:00
Sunil Mushran
18c50cb0d3 ocfs2/cluster: Print messages when adding/removing heartbeat regions
Prints messages when the user adds or removes heartbeat regions in global
heartbeat mode. These messages are useful when debugging cluster related issues.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 18:26:59 -07:00
Sunil Mushran
18cfdf1b1a ocfs2/dlm: Add message DLM_QUERY_NODEINFO
Adds new dlm message DLM_QUERY_NODEINFO that sends the attributes of all
registered nodes. This message is sent if the negotiated dlm protocol is
1.1 or higher. If the information of the joining node does not match
that of any existing nodes, the join domain request is rejected.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 16:47:03 -07:00
Sunil Mushran
5f3c6d9c61 ocfs2: Print message if user mounts without starting global heartbeat
In global heartbeat mode, the heartbeat is started by the user. This patch
prints an error if the user attempts to mount a volume without starting the
heartbeat.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:29 -07:00
Sunil Mushran
ea2034416b ocfs2/dlm: Add message DLM_QUERY_REGION
Adds new dlm message DLM_QUERY_REGION that sends the names of all active
heartbeat regions. This message is only sent in the global heartbeat
mode. If the regions in the joining node do not fully match the ones in
the active nodes, the join domain request is rejected.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-09 10:26:23 -07:00
Sunil Mushran
b3c85c4cdf ocfs2/cluster: Get all heartbeat regions
Export function in o2hb to get a list of heartbeat regions. It also adds an
upper limit to the length of the heartbeat region name.

o2hb_global_heartbeat_active() currently disables global heartbeat. It will
be enabled in a later patch after all the code is added.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 14:31:06 -07:00
Sunil Mushran
b1365d0bd1 ocfs2/dlm: Expose dlm_protocol in dlm_state
Add dlm_protocol to the list of info shown by the debugfs file, dlm_state.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-06 17:55:34 -07:00
Sunil Mushran
2c442719e9 ocfs2: Add support for heartbeat=global mount option
Adds support for heartbeat=global mount option. It ensures that the heartbeat
mode passed matches the one enabled on disk.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 15:23:50 -07:00
Sunil Mushran
98f486f23b ocfs2: Add an incompat feature flag OCFS2_FEATURE_INCOMPAT_CLUSTERINFO
OCFS2_FEATURE_INCOMPAT_CLUSTERINFO allows us to use sb->s_cluster_info for
both userspace and o2cb cluster stacks. It also allows us to extend cluster
info to include stack flags.

This patch also adds stackflags to sb->s_clusterinfo. It also introduces a
clusterinfo flag OCFS2_CLUSTER_O2CB_GLOBAL_HEARTBEAT to denote the enabled
global heartbeat mode.

This incompat flag can be set/cleared using tunefs.ocfs2 --fs-features. The
clusterinfo flag is set/cleared using tunefs.ocfs2 --update-cluster-stack.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-09 10:24:46 -07:00
Sunil Mushran
54b5187b5a ocfs2/cluster: Add heartbeat mode configfs parameter
Add heartbeat mode parameter to the configfs tree. This will be used
to set/show the heartbeat mode. The user is free to toggle the mode
between local and global as long as there is no active heartbeat region.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
2010-10-07 15:26:08 -07:00
Linus Torvalds
cb655d0f3d Linux 2.6.36-rc7 2010-10-06 13:39:52 -07:00
Linus Torvalds
81c20b96e5 Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/upstream-linus
* 'upstream' of git://git.linux-mips.org/pub/scm/upstream-linus:
  MIPS: Octeon: Place cnmips_cu2_setup in __init memory.
  MIPS: Don't place cu2 notifiers in __cpuinitdata
  MIPS: Calculate VMLINUZ_LOAD_ADDRESS based on the length of vmlinux.bin
  MIPS: Alchemy: Resolve prom section mismatches
  MIPS: Fix syscall 64 bit number comments.
  MIPS: Hookup fanotify_init, fanotify_mark, and prlimit64 syscalls.
  MIPS: TX49xx: Rename ARCH_KMALLOC_MINALIGN to ARCH_DMA_MINALIGN
  MIPS: N32: Fix getdents64 syscall for n32
  MIPS: Remove pr_<level> uses of KERN_<level>
  MIPS: PNX8550: Sort out machine halt, restart and powerdown functions.
  MIPS: GIC: Remove dependencies from Malta files.
  MIPS: Kconfig: Fix and clarify kconfig help text for VSMP and SMTC.
  MIPS: DMA: Fix computation of DMA flags from device's coherent_dma_mask.
  MIPS: Audit: Fix hang in entry.S.
  MIPS: Document why RELOC_HIDE is there.
  MIPS: Octeon: Determine if helper needs to be built
  MIPS: Use generic atomic64 for 32-bit kernels
  MIPS: RM7000: Symbol should be static
  MIPS: kspd: Adjust confusing if indentation
  MIPS: Fix a typo.
2010-10-06 13:27:19 -07:00
Linus Torvalds
089eed29b4 Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block
* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  writeback: always use sb->s_bdi for writeback purposes
2010-10-06 11:11:18 -07:00
Linus Torvalds
34984f54b7 Merge branch 'v2.6.36-rc6-urgent-fixes' of git://xenbits.xen.org/people/sstabellini/linux-pvhvm
* 'v2.6.36-rc6-urgent-fixes' of git://xenbits.xen.org/people/sstabellini/linux-pvhvm:
  xen: do not initialize PV timers on HVM if !xen_have_vector_callback
  xen: do not set xenstored_ready before xenbus_probe on hvm
2010-10-06 09:51:28 -07:00
Linus Torvalds
8fe9793af0 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Initialize total_len in fuse_retrieve()
2010-10-06 09:50:41 -07:00
Stephen Rothwell
7c6d45e665 powerpc: remove unused variable
Since powerpc uses -Werror on arch powerpc, the build was broken like
this:

  cc1: warnings being treated as errors
  arch/powerpc/kernel/module.c: In function 'module_finalize':
  arch/powerpc/kernel/module.c:66: error: unused variable 'err'

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-05 17:27:54 -07:00
Linus Torvalds
e1d9694cae Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: rcu_read_lock_bh_held(): disabling irqs also disables bh
  generic-ipi: Fix deadlock in __smp_call_function_single
2010-10-05 13:07:43 -07:00
Linus Torvalds
39c12be86a Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  perf trace scripting: Fix extern struct definitions
  perf ui hist browser: Fix segfault on 'a' for annotate
  perf tools: Fix build breakage
  perf, x86: Handle in flight NMIs on P4 platform
  oprofile, ARM: Release resources on failure
  oprofile: Add Support for Intel CPU Family 6 / Model 29
2010-10-05 11:57:37 -07:00
Evgeny Kuznetsov
231d0aefd8 wait: using uninitialized member of wait queue
The "flags" member of "struct wait_queue_t" is used in several places in
the kernel code without beeing initialized by init_wait().  "flags" is
used in bitwise operations.

If "flags" not initialized then unexpected behaviour may take place.
Incorrect flags might used later in code.

Added initialization of "wait_queue_t.flags" with zero value into
"init_wait".

Signed-off-by: Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@nokia.com>
[ The bit we care about does end up being initialized by both
   prepare_to_wait() and add_to_wait_queue(), so this doesn't seem to
   cause actual bugs, but is definitely the right thing to do -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-05 11:47:18 -07:00
Linus Torvalds
5336377d62 modules: Fix module_bug_list list corruption race
With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.

Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-05 11:29:27 -07:00
Stefano Stabellini
31e7e931cd xen: do not initialize PV timers on HVM if !xen_have_vector_callback
if !xen_have_vector_callback do not initialize PV timer unconditionally
because we still don't know how many cpus are available and if there is
more than one we won't be able to receive the timer interrupts on
cpu > 0.

This patch fixes an hang at boot when Xen does not support vector
callbacks and the guest has multiple vcpus.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
2010-10-05 13:39:23 +01:00
Stefano Stabellini
a947f0f8f7 xen: do not set xenstored_ready before xenbus_probe on hvm
Register_xenstore_notifier should guarantee that the caller gets
notified even if xenstore is already up.
Therefore we revert "do not notify callers from
register_xenstore_notifier" and set xenstored_read at the right time for
PV on HVM guests too.
In fact in case of PV on HVM guests xenstored is ready only after the
platform pci driver has completed the initialization, so do not set
xenstored_ready before the call to xenbus_probe().

This patch fixes a shutdown_event watcher registration bug that causes
"xm shutdown" not to work properly.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
2010-10-05 13:37:28 +01:00
Linus Torvalds
2f6b3aa7a5 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lrg/voltage-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lrg/voltage-2.6:
  regulator: max8649 - fix setting extclk_freq
  regulator: fix typo in current units
  regulator: fix device_register() error handling
2010-10-04 13:35:48 -07:00
Linus Torvalds
3c06806e69 Merge branch 'merge-powerpc' of git://git.secretlab.ca/git/linux-2.6
* 'merge-powerpc' of git://git.secretlab.ca/git/linux-2.6:
  powerpc/5200: tighten up ac97 reset timing
  powerpc/5200: efika.c: Add of_node_put to avoid memory leak
  powerpc/512x: fix clk_get() return value
2010-10-04 11:45:35 -07:00
Linus Torvalds
d9f73afcd3 Merge branch 'fix/misc' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6
* 'fix/misc' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
  ALSA: i2c/other/ak4xx-adda: Fix a compile warning with CONFIG_PROCFS=n
  ALSA: prevent heap corruption in snd_ctl_new()
2010-10-04 11:15:59 -07:00
Linus Torvalds
53d22d886a Merge branch 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/staging
* 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/staging:
  hwmon: f71882fg: use a muxed resource lock for the Super I/O port
2010-10-04 11:15:06 -07:00
Linus Torvalds
5a4bbd01c8 Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
  [CPUFREQ] Fix memory leaks in pcc_cpufreq_do_osc
  [CPUFREQ] acpi-cpufreq: add missing __percpu markup
2010-10-04 11:14:21 -07:00
Linus Torvalds
989cd445b4 Merge branch 'merge-spi' of git://git.secretlab.ca/git/linux-2.6
* 'merge-spi' of git://git.secretlab.ca/git/linux-2.6:
  of/spi: Fix OF-style driver binding of spi devices
  spi: spi-gpio.c tests SPI_MASTER_NO_RX bit twice, but not SPI_MASTER_NO_TX
  spi/mpc8xxx: fix buffer overrun on large transfers
2010-10-04 11:13:22 -07:00
Linus Torvalds
4a73a43741 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6:
  vlan: dont drop packets from unknown vlans in promiscuous mode
  Phonet: Correct header retrieval after pskb_may_pull
  um: Proper Fix for f25c80a4: remove duplicate structure field initialization
  ip_gre: Fix dependencies wrt. ipv6.
  net-2.6: SYN retransmits: Add new parameter to retransmits_timed_out()
  iwl3945: queue the right work if the scan needs to be aborted
  mac80211: fix use-after-free
2010-10-04 11:11:01 -07:00
Linus Torvalds
c470af0a27 Merge branch 'drm-intel-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ickle/drm-intel
* 'drm-intel-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ickle/drm-intel:
  drm/i915: Rephrase pwrite bounds checking to avoid any potential overflow
  drm/i915: Sanity check pread/pwrite
  drm/i915: Use pipe state to tell when pipe is off
  drm/i915: vblank status not valid while training display port
  drivers/gpu/drm/i915/i915_gem.c: Add missing error handling code
  drm/i915: Fix refleak during eviction.
  drm/i915: fix GMCH power reporting
2010-10-04 11:10:26 -07:00
Hugh Dickins
4e31635c36 ksm: fix bad user data when swapping
Building under memory pressure, with KSM on 2.6.36-rc5, collapsed with
an internal compiler error: typically indicating an error in swapping.

Perhaps there's a timing issue which makes it now more likely, perhaps
it's just a long time since I tried for so long: this bug goes back to
KSM swapping in 2.6.33.

Notice how reuse_swap_page() allows an exclusive page to be reused, but
only does SetPageDirty if it can delete it from swap cache right then -
if it's currently under Writeback, it has to be left in cache and we
don't SetPageDirty, but the page can be reused.  Fine, the dirty bit
will get set in the pte; but notice how zap_pte_range() does not bother
to transfer pte_dirty to page_dirty when unmapping a PageAnon.

If KSM chooses to share such a page, it will look like a clean copy of
swapcache, and not be written out to swap when its memory is needed;
then stale data read back from swap when it's needed again.

We could fix this in reuse_swap_page() (or even refuse to reuse a
page under writeback), but it's more honest to fix my oversight in
KSM's write_protect_page().  Several days of testing on three machines
confirms that this fixes the issue they showed.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-04 11:09:53 -07:00