- 23 Mar, 2011 33 commits
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Prarit Bhargava authored
While looking at some other notifier callbacks I noticed this code could use a simple cleanup. notifier_from_errno() no longer needs the if (ret)/else conditional. That same conditional is now done in notifier_from_errno(). Signed-off-by:
Prarit Bhargava <prarit@redhat.com> Cc: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Acked-by:
Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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David Rientjes authored
Displaying extremely verbose meminfo for all nodes on the system is overkill for page allocation failures when the context restricts that allocation to only a subset of nodes. We don't particularly care about the state of all nodes when some are not allowed in the current context, they can have an abundance of memory but we can't allocate from that part of memory. This patch suppresses disallowed nodes from the meminfo dump on a page allocation failure if the context requires it. Signed-off-by:
David Rientjes <rientjes@google.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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David Rientjes authored
When a page allocation failure occurs, show_mem() is called to dump the state of the VM so users may understand what happened to get into that condition. This output, however, can be extremely verbose. In irq context, it may result in significant delays that incur NMI watchdog timeouts when the machine is large (we use CONFIG_NODES_SHIFT > 8 here to define a "large" machine since the length of the show_mem() output is proportional to the number of possible nodes). This patch suppresses the show_mem() call in irq context when the kernel has CONFIG_NODES_SHIFT > 8. Signed-off-by:
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David Rientjes authored
The oom killer is extremely verbose for machines with a large number of cpus and/or nodes. This verbosity can often be harmful if it causes other important messages to be scrolled from the kernel log and incurs a signicant time delay, specifically for kernels with CONFIG_NODES_SHIFT > 8. This patch causes only memory information to be displayed for nodes that are allowed by current's cpuset when dumping the VM state. Information for all other nodes is irrelevant to the oom condition; we don't care if there's an abundance of memory elsewhere if we can't access it. This only affects the behavior of dumping memory information when an oom is triggered. Other dumps, such as for sysrq+m, still display the unfiltered form when using the existing show_mem() interface. Additionally, the per-cpu pageset statistics are extremely verbose in oom killer output, so it is now suppressed. This removes nodes_weight(current->mems_allowed) * (1 + nr_cpus) lines from the oom killer output. Callers may use __show_mem(SHOW_MEM_FILTER_NODES) to filter disallowed nodes. Signed-off-by:
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Eric Dumazet authored
ksoftirqd, kworker, migration, and pktgend kthreads can be created with kthread_create_on_node(), to get proper NUMA affinities for their stack and task_struct. Signed-off-by:
Eric Dumazet <eric.dumazet@gmail.com> Acked-by:
David S. Miller <davem@davemloft.net> Reviewed-by:
Andi Kleen <ak@linux.intel.com> Acked-by:
Rusty Russell <rusty@rustcorp.com.au> Acked-by:
Tejun Heo <tj@kernel.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: David Howells <dhowells@redhat.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by:
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Eric Dumazet authored
All kthreads being created from a single helper task, they all use memory from a single node for their kernel stack and task struct. This patch suite creates kthread_create_on_node(), adding a 'cpu' parameter to parameters already used by kthread_create(). This parameter serves in allocating memory for the new kthread on its memory node if possible. Signed-off-by:
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Eric Dumazet authored
Add a node parameter to alloc_thread_info(), and change its name to alloc_thread_info_node() This change is needed to allow NUMA aware kthread_create_on_cpu() Signed-off-by:
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Eric Dumazet authored
All kthreads being created from a single helper task, they all use memory from a single node for their kernel stack and task struct. This patch suite creates kthread_create_on_cpu(), adding a 'cpu' parameter to parameters already used by kthread_create(). This parameter serves in allocating memory for the new kthread on its memory node if available. Users of this new function are : ksoftirqd, kworker, migration, pktgend... This patch: Add a node parameter to alloc_task_struct(), and change its name to alloc_task_struct_node() This change is needed to allow NUMA aware kthread_create_on_cpu() Signed-off-by:
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Minchan Kim authored
Many migrate_page's caller check return value instead of list_empy by cf608ac1 ("mm: compaction: fix COMPACTPAGEFAILED counting"). This patch makes compaction's migrate_pages consistent with others. This patch should not change old behavior. Signed-off-by:
Minchan Kim <minchan.kim@gmail.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christoph Lameter <cl@linux.com> Signed-off-by:
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Andrea Arcangeli authored
This patch reverts 5a03b051 ("thp: use compaction in kswapd for GFP_ATOMIC order > 0") due to reports stating that kswapd CPU usage was higher and IRQs were being disabled more frequently. This was reported at http://www.spinics.net/linux/fedora/alsa-user/msg09885.html. Without this patch applied, CPU usage by kswapd hovers around the 20% mark according to the tester (Arthur Marsh: http://www.spinics.net/linux/fedora/alsa-user/msg09899.html). With this patch applied, it's around 2%. The problem is not related to THP which specifies __GFP_NO_KSWAPD but is triggered by high-order allocations hitting the low watermark for their order and waking kswapd on kernels with CONFIG_COMPACTION set. The most common trigger for this is network cards configured for jumbo frames but it's also possible it'll be triggered by fork-heavy workloads (order-1) and some wireless cards which depend on order-1 allocations. The symptoms for the user will be high CPU usage by kswapd in low-memory situations which could be confused with another writeback problem. While a patch like 5a03b051 may be reintroduced in the future, this patch plays it safe for now and reverts it. [mel@csn.ul.ie: Beefed up the changelog] Signed-off-by:
Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
Mel Gorman <mel@csn.ul.ie> Reported-by:
Arthur Marsh <arthur.marsh@internode.on.net> Tested-by:
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Nick Piggin authored
Provide a free area cache for the vmalloc virtual address allocator, based on the algorithm used by the user virtual memory allocator. This reduces the number of rbtree operations and linear traversals over the vmap extents in order to find a free area, by starting off at the last point that a free area was found. The free area cache is reset if areas are freed behind it, or if we are searching for a smaller area or alignment than last time. So allocation patterns are not changed (verified by corner-case and random test cases in userspace testing). This solves a regression caused by lazy vunmap TLB purging introduced in db64fe02 (mm: rewrite vmap layer). That patch will leave extents in the vmap allocator after they are vunmapped, and until a significant number accumulate that can be flushed in a single batch. So in a workload that vmalloc/vfree frequently, a chain of extents will build up from VMALLOC_START address, which have to be iterated over each time (giving an O(n) type of behaviour). After this patch, the search will start from where it left off, giving closer to an amortized O(1). This is verified to solve regressions reported Steven in GFS2, and Avi in KVM. Hugh's update: : I tried out the recent mmotm, and on one machine was fortunate to hit : the BUG_ON(first->va_start < addr) which seems to have been stalling : your vmap area cache patch ever since May. : I can get you addresses etc, I did dump a few out; but once I stared : at them, it was easier just to look at the code: and I cannot see how : you would be so sure that first->va_start < addr, once you've done : that addr = ALIGN(max(...), align) above, if align is over 0x1000 : (align was 0x8000 or 0x4000 in the cases I hit: ioremaps like Steve). : I originally got around it by just changing the : if (first->va_start < addr) { : to : while (first->va_start < addr) { : without thinking about it any further; but that seemed unsatisfactory, : why would we want to loop here when we've got another very similar : loop just below it? : I am never going to admit how long I've spent trying to grasp your : "while (n)" rbtree loop just above this, the one with the peculiar : if (!first && tmp->va_start < addr + size) : in. That's unfamiliar to me, I'm guessing it's designed to save a : subsequent rb_next() in a few circumstances (at risk of then setting : a wrong cached_hole_size?); but they did appear few to me, and I didn't : feel I could sign off something with that in when I don't grasp it, : and it seems responsible for extra code and mistaken BUG_ON below it. : I've reverted to the familiar rbtree loop that find_vma() does (but : with va_end >= addr as you had, to respect the additional guard page): : and then (given that cached_hole_size starts out 0) I don't see the : need for any complications below it. If you do want to keep that loop : as you had it, please add a comment to explain what it's trying to do, : and where addr is relative to first when you emerge from it. : Aren't your tests "size <= cached_hole_size" and : "addr + size > first->va_start" forgetting the guard page we want : before the next area? I've changed those. : I have not changed your many "addr + size - 1 < addr" overflow tests, : but have since come to wonder, shouldn't they be "addr + size < addr" : tests - won't the vend checks go wrong if addr + size is 0? : I have added a few comments - Wolfgang Wander's 2.6.13 description of : 1363c3cd Avoiding mmap fragmentation : helped me a lot, perhaps a pointer to that would be good too. And I found : it easier to understand when I renamed cached_start slightly and moved the : overflow label down. : This patch would go after your mm-vmap-area-cache.patch in mmotm. : Trivially, nobody is going to get that BUG_ON with this patch, and it : appears to work fine on my machines; but I have not given it anything like : the testing you did on your original, and may have broken all the : performance you were aiming for. Please take a look and test it out : integrate with yours if you're satisfied - thanks. [akpm@linux-foundation.org: add locking comment] Signed-off-by:
Nick Piggin <npiggin@suse.de> Signed-off-by:
Hugh Dickins <hughd@google.com> Reviewed-by:
Steven Whitehouse <swhiteho@redhat.com> Reported-and-tested-by:
Avi Kivity <avi@redhat.com> Tested-by:
"Barry J. Marson" <bmarson@redhat.com> Cc: Prarit Bhargava <prarit@redhat.com> Signed-off-by:
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Robert Morell authored
In systems with multiple framebuffer devices, one of the devices might be blanked while another is unblanked. In order for the backlight blanking logic to know whether to turn off the backlight for a particular framebuffer's blanking notification, it needs to be able to check if a given framebuffer device corresponds to the backlight. This plumbs the check_fb hook from core backlight through the pwm_backlight helper to allow platform code to plug in a check_fb hook. Signed-off-by:
Robert Morell <rmorell@nvidia.com> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Arun Murthy <arun.murthy@stericsson.com> Cc: Linus Walleij <linus.walleij@stericsson.com> Signed-off-by:
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Axel Lin authored
The following symbols are needlessly defined global: jornada_bl_init, jornada_bl_exit, jornada_lcd_init, jornada_lcd_exit. Make them static. Signed-off-by:
Axel Lin <axel.lin@gmail.com> Acked-by:
Kristoffer Ericson <kristoffer.ericson@gmail.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Randy Dunlap authored
apple_bl uses ACPI interfaces (data & code), so it should depend on ACPI. drivers/video/backlight/apple_bl.c:142: warning: 'struct acpi_device' declared inside parameter list drivers/video/backlight/apple_bl.c:142: warning: its scope is only this definition or declaration, which is probably not what you want drivers/video/backlight/apple_bl.c:201: warning: 'struct acpi_device' declared inside parameter list drivers/video/backlight/apple_bl.c:215: error: variable 'apple_bl_driver' has initializer but incomplete type drivers/video/backlight/apple_bl.c:216: error: unknown field 'name' specified in initializer ... Signed-off-by:
Randy Dunlap <randy.dunlap@oracle.com> Acked-by:
Matthew Garrett <mjg@redhat.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Matthew Garrett authored
It works on hardware other than Macbook Pros, and it works on GPUs other than Nvidia. It should even work on iMacs, so change the name to match reality more precisely and include an alias so existing users don't get confused. Signed-off-by:
Richard Purdie <richard.purdie@linuxfoundation.org> Cc: Mourad De Clerck <mourad@aquazul.com> Signed-off-by:
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Matthew Garrett authored
The SMI-based backlight control functionality may fail to work if the system is running under EFI rather than BIOS. Check that the hardware responds as expected, and exit if it doesn't. Signed-off-by:
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Matthew Garrett authored
This driver only has to deal with two different classes of hardware, but right now it needs new DMI entries for every new machine. It turns out that there's an ACPI device that uniquely identifies Apples with backlights, so this patch reworks the driver into an ACPI one, identifies the hardware by checking the PCI vendor of the root bridge and strips out all the DMI code. It also changes the config text to clarify that it works on devices other than Macbook Pros and GPUs other than nvidia. Signed-off-by:
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Matthew Garrett authored
Dual-GPU machines may provide more than one ACPI backlight interface. Tie the backlight device to the GPU in order to allow userspace to identify the correct interface. Signed-off-by:
Sedat Dilek <sedat.dilek@googlemail.com> Signed-off-by:
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Matthew Garrett authored
We may eventually end up with per-connector backlights, especially with ddcci devices. Make sure that the parent node for the backlight device is the connector rather than the PCI device. Signed-off-by:
Ben Skeggs <bskeggs@redhat.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Tested-by:
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Michel Dänzer authored
Allows e.g. power management daemons to control the backlight level. Inspired by the corresponding code in radeonfb. [mjg@redhat.com: updated to add backlight type and make the connector the parent device] Signed-off-by:
Michel Dänzer <michel@daenzer.net> Signed-off-by:
Alex Deucher <alexdeucher@gmail.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Tested-by:
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Matthew Garrett authored
There may be multiple ways of controlling the backlight on a given machine. Allow drivers to expose the type of interface they are providing, making it possible for userspace to make appropriate policy decisions. Signed-off-by:
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Vasiliy Kulikov authored
Don't allow everybody to change LED settings. Signed-off-by:
Vasiliy Kulikov <segoon@openwall.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Vasiliy Kulikov authored
Don't allow everybody to change LED settings. Signed-off-by:
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Donghwa Lee authored
Add a ld9040 amoled panel driver. Signed-off-by:
Donghwa Lee <dh09.lee@samsung.com> Signed-off-by:
Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by:
Inki Dae <inki.dae@samsung.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Uwe Kleine-König authored
And fix a typo. Signed-off-by:
Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Shreshtha Kumar Sahu authored
Simple backlight driver for National Semiconductor LM3530. Presently only manual mode is supported, PWM and ALS support to be added. Signed-off-by:
Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> Cc: Linus Walleij <linus.walleij@stericsson.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Mark Brown authored
There is a move to deprecate bus-specific PM operations and move to using dev_pm_ops instead in order to reduce the amount of boilerplate code in buses and facilitiate updates to the PM core. Do this move for the bs2802 driver. [akpm@linux-foundation.org: fix warnings] Signed-off-by:
Mark Brown <broonie@opensource.wolfsonmicro.com> Cc: Kim Kyuwon <q1.kim@samsung.com> Cc: Kim Kyuwon <chammoru@gmail.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by:
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Phil Carmody authored
list_del() leaves poison in the prev and next pointers. The next list_empty() will compare those poisons, and say the list isn't empty. Any list operations that assume the node is on a list because of such a check will be fooled into dereferencing poison. One needs to INIT the node after the del, and fortunately there's already a wrapper for that - list_del_init(). Some of the dels are followed by deallocations, so can be ignored, and one can be merged with an add to make a move. Apart from that, I erred on the side of caution in making nodes list_empty()-queriable. Signed-off-by:
Phil Carmody <ext-phil.2.carmody@nokia.com> Reviewed-by:
Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Acked-by:
Kirill A. Shutemov <kirill@shutemov.name> Cc: <stable@kernel.org> Signed-off-by:
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David Rientjes authored
The oom killer naturally defers killing anything if it finds an eligible task that is already exiting and has yet to detach its ->mm. This avoids unnecessarily killing tasks when one is already in the exit path and may free enough memory that the oom killer is no longer needed. This is detected by PF_EXITING since threads that have already detached its ->mm are no longer considered at all. The problem with always deferring when a thread is PF_EXITING, however, is that it may never actually exit when being traced, specifically if another task is tracing it with PTRACE_O_TRACEEXIT. The oom killer does not want to defer in this case since there is no guarantee that thread will ever exit without intervention. This patch will now only defer the oom killer when a thread is PF_EXITING and no ptracer has stopped its progress in the exit path. It also ensures that a child is sacrificed for the chosen parent only if it has a different ->mm as the comment implies: this ensures that the thread group leader is always targeted appropriately. Signed-off-by:
Oleg Nesterov <oleg@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Cc: Andrey Vagin <avagin@openvz.org> Cc: <stable@kernel.org> [2.6.38.x] Signed-off-by:
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Andrey Vagin authored
We shouldn't defer oom killing if a thread has already detached its ->mm and still has TIF_MEMDIE set. Memory needs to be freed, so find kill other threads that pin the same ->mm or find another task to kill. Signed-off-by:
Andrey Vagin <avagin@openvz.org> Signed-off-by:
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David Rientjes authored
This patch prevents unnecessary oom kills or kernel panics by reverting two commits: 495789a5 (oom: make oom_score to per-process value) cef1d352 (oom: multi threaded process coredump don't make deadlock) First, 495789a5 (oom: make oom_score to per-process value) ignores the fact that all threads in a thread group do not necessarily exit at the same time. It is imperative that select_bad_process() detect threads that are in the exit path, specifically those with PF_EXITING set, to prevent needlessly killing additional tasks. If a process is oom killed and the thread group leader exits, select_bad_process() cannot detect the other threads that are PF_EXITING by iterating over only processes. Thus, it currently chooses another task unnecessarily for oom kill or panics the machine when nothing else is eligible. By iterating over threads instead, it is possible to detect threads that are exiting and nominate them for oom kill so they get access to memory reserves. Second, cef1d352 (oom: multi threaded process coredump don't make deadlock) erroneously avoids making the oom killer a no-op when an eligible thread other than current isfound to be exiting. We want to detect this situation so that we may allow that exiting thread time to exit and free its memory; if it is able to exit on its own, that should free memory so current is no loner oom. If it is not able to exit on its own, the oom killer will nominate it for oom kill which, in this case, only means it will get access to memory reserves. Without this change, it is easy for the oom killer to unnecessarily target tasks when all threads of a victim don't exit before the thread group leader or, in the worst case, panic the machine. Signed-off-by:
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Mel Gorman authored
If an administrator tries to swapon a file backed by NFS, the inode mutex is taken (as it is for any swapfile) but later identified to be a bad swapfile due to the lack of bmap and tries to cleanup. During cleanup, an attempt is made to close the file but with inode->i_mutex still held. Closing an NFS file syncs it which tries to acquire the inode mutex leading to deadlock. If lockdep is enabled the following appears on the console; ============================================= [ INFO: possible recursive locking detected ] 2.6.38-rc8-autobuild #1 --------------------------------------------- swapon/2192 is trying to acquire lock: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: vfs_fsync_range+0x47/0x7c but task is already holding lock: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7 other info that might help us debug this: 1 lock held by swapon/2192: #0: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7 stack backtrace: Pid: 2192, comm: swapon Not tainted 2.6.38-rc8-autobuild #1 Call Trace: __lock_acquire+0x2eb/0x1623 find_get_pages_tag+0x14a/0x174 pagevec_lookup_tag+0x25/0x2e vfs_fsync_range+0x47/0x7c lock_acquire+0xd3/0x100 vfs_fsync_range+0x47/0x7c nfs_flush_one+0x0/0xdf [nfs] mutex_lock_nested+0x40/0x2b1 vfs_fsync_range+0x47/0x7c vfs_fsync_range+0x47/0x7c vfs_fsync+0x1c/0x1e nfs_file_flush+0x64/0x69 [nfs] filp_close+0x43/0x72 sys_swapon+0xa39/0xae7 sysret_check+0x2e/0x69 system_call_fastpath+0x16/0x1b This patch releases the mutex if its held before calling filep_close() so swapon fails as expected without deadlock when the swapfile is backed by NFS. If accepted for 2.6.39, it should also be considered a -stable candidate for 2.6.38 and 2.6.37. Signed-off-by:Mel Gorman <mgorman@suse.de> Acked-by:
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Andrew Morton authored
syncfs() is duplicating name_to_handle_at() due to a merging mistake. Cc: Sage Weil <sage@newdream.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by:
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- 22 Mar, 2011 7 commits
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git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6Linus Torvalds authored
* 'slab/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6: slub: Add statistics for this_cmpxchg_double failures slub: Add missing irq restore for the OOM path
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git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fsLinus Torvalds authored
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs: [net/9p]: Introduce basic flow-control for VirtIO transport. 9p: use the updated offset given by generic_write_checks [net/9p] Don't re-pin pages on retrying virtqueue_add_buf(). [net/9p] Set the condition just before waking up. [net/9p] unconditional wake_up to proc waiting for space on VirtIO ring fs/9p: Add v9fs_dentry2v9ses fs/9p: Attach writeback_fid on first open with WR flag fs/9p: Open writeback fid in O_SYNC mode fs/9p: Use truncate_setsize instead of vmtruncate net/9p: Fix compile warning net/9p: Convert the in the 9p rpc call path to GFP_NOFS fs/9p: Fix race in initializing writeback fid
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git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-clientLinus Torvalds authored
* git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: rbd: use watch/notify for changes in rbd header libceph: add lingering request and watch/notify event framework rbd: update email address in Documentation ceph: rename dentry_release -> d_release, fix comment ceph: add request to the tail of unsafe write list ceph: remove request from unsafe list if it is canceled/timed out ceph: move readahead default to fs/ceph from libceph ceph: add ino32 mount option ceph: update common header files ceph: remove debugfs debug cruft libceph: fix osd request queuing on osdmap updates ceph: preserve I_COMPLETE across rename libceph: Fix base64-decoding when input ends in newline.
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Linus Torvalds authored
Using delayed-work for tty flip buffers ends up causing us to wait for the next tick to complete some actions. That's usually not all that noticeable, but for certain latency-critical workloads it ends up being totally unacceptable. As an extreme case of this, passing a token back-and-forth over a pty will take two ticks per iteration, so even just a thousand iterations will take 8 seconds assuming a common 250Hz configuration. Avoiding the whole delayed work issue brings that ping-pong test-case down to 0.009s on my machine. In more practical terms, this latency has been a performance problem for things like dive computer simulators (simulating the serial interface using the ptys) and for other environments (Alan mentions a CP/M emulator). Reported-by:
Jef Driesen <jefdriesen@telenet.be> Acked-by:
Greg KH <gregkh@suse.de> Acked-by:
Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by:
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Venkateswararao Jujjuri (JV) authored
Recent zerocopy work in the 9P VirtIO transport maps and pins user buffers into kernel memory for the server to work on them. Since the user process can initiate this kind of pinning with a simple read/write call, thousands of IO threads initiated by the user process can hog the system resources and could result into denial of service. This patch introduces flow control to avoid that extreme scenario. The ceiling limit to avoid denial of service attacks is set to relatively high (nr_free_pagecache_pages()/4) so that it won't interfere with regular usage, but can step in extreme cases to limit the total system hang. Since we don't have a global structure to accommodate this variable, I choose the virtio_chan as the home for this. Signed-off-by:
Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com> Reviewed-by:
Badari Pulavarty <pbadari@us.ibm.com> Signed-off-by:
Eric Van Hensbergen <ericvh@gmail.com>
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M. Mohan Kumar authored
Without this fix, even if a file is opened in O_APPEND mode, data will be written at current file position instead of end of file. Signed-off-by:
M. Mohan Kumar <mohan@in.ibm.com> Reviewed-by:
Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by:
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Venkateswararao Jujjuri (JV) authored
Signed-off-by:
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