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* shmem: put_super must percpu_counter_destroyHugh Dickins2010-08-171-2/+6
| | | | | | | | | | list_add() corruption messages reported from shmem_fill_super()'s recently introduced percpu_counter_init(): shmem_put_super() needs to remember to percpu_counter_destroy(). And also check error from percpu_counter_init(). Reported-bisected-and-tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: fix up some user-visible effects of the stack guard pageLinus Torvalds2010-08-151-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit makes the stack guard page somewhat less visible to user space. It does this by: - not showing the guard page in /proc/<pid>/maps It looks like lvm-tools will actually read /proc/self/maps to figure out where all its mappings are, and effectively do a specialized "mlockall()" in user space. By not showing the guard page as part of the mapping (by just adding PAGE_SIZE to the start for grows-up pages), lvm-tools ends up not being aware of it. - by also teaching the _real_ mlock() functionality not to try to lock the guard page. That would just expand the mapping down to create a new guard page, so there really is no point in trying to lock it in place. It would perhaps be nice to show the guard page specially in /proc/<pid>/maps (or at least mark grow-down segments some way), but let's not open ourselves up to more breakage by user space from programs that depends on the exact deails of the 'maps' file. Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools source code to see what was going on with the whole new warning. Reported-and-tested-by: François Valenduc <francois.valenduc@tvcablenet.be Reported-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm/page-writeback: fix non-kernel-doc function commentsRandy Dunlap2010-08-141-2/+2
| | | | | | | | Remove leading /** from non-kernel-doc function comments to prevent kernel-doc warnings. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: fix page table unmap for stack guard page properlyLinus Torvalds2010-08-141-7/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | We do in fact need to unmap the page table _before_ doing the whole stack guard page logic, because if it is needed (mainly 32-bit x86 with PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it will do a kmap_atomic/kunmap_atomic. And those kmaps will create an atomic region that we cannot do allocations in. However, the whole stack expand code will need to do anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an atomic region. Now, a better model might actually be to do the anon_vma_prepare() when _creating_ a VM_GROWSDOWN segment, and not have to worry about any of this at page fault time. But in the meantime, this is the straightforward fix for the issue. See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details. Reported-by: Wylda <wylda@volny.cz> Reported-by: Sedat Dilek <sedat.dilek@gmail.com> Reported-by: Mike Pagano <mpagano@gentoo.org> Reported-by: François Valenduc <francois.valenduc@tvcablenet.be> Tested-by: Ed Tomlinson <edt@aei.ca> Cc: Pekka Enberg <penberg@kernel.org> Cc: Greg KH <gregkh@suse.de> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* NOMMU: Remove an extraneous no_printk()David Howells2010-08-131-5/+0
| | | | | | | | | | | | | | | | Remove an extraneous no_printk() in mm/nommu.c that got missed when the function got generalised from several things that used it in commit 12fdff3fc248 ("Add a dummy printk function for the maintenance of unused printks"). Without this, the following error is observed: mm/nommu.c:41: error: conflicting types for 'no_printk' include/linux/kernel.h:314: error: previous definition of 'no_printk' was here Reported-by: Michal Simek <monstr@monstr.eu> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: fix missing page table unmap for stack guard page failure caseLinus Torvalds2010-08-131-1/+3
| | | | | | | | .. which didn't show up in my tests because it's a no-op on x86-64 and most other architectures. But we enter the function with the last-level page table mapped, and should unmap it at exit. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: keep a guard page below a grow-down stack segmentLinus Torvalds2010-08-121-0/+23
| | | | | | | | | | | | | | | | | | | | | This is a rather minimally invasive patch to solve the problem of the user stack growing into a memory mapped area below it. Whenever we fill the first page of the stack segment, expand the segment down by one page. Now, admittedly some odd application might _want_ the stack to grow down into the preceding memory mapping, and so we may at some point need to make this a process tunable (some people might also want to have more than a single page of guarding), but let's try the minimal approach first. Tested with trivial application that maps a single page just below the stack, and then starts recursing. Without this, we will get a SIGSEGV _after_ the stack has smashed the mapping. With this patch, we'll get a nice SIGBUS just as the stack touches the page just above the mapping. Requested-by: Keith Packard <keithp@keithp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'hwpoison' of ↵Linus Torvalds2010-08-124-38/+260
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6 * 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6: hugetlb: add missing unlock in avoidcopy path in hugetlb_cow() hwpoison: rename CONFIG HWPOISON, hugetlb: support hwpoison injection for hugepage HWPOISON, hugetlb: detect hwpoison in hugetlb code HWPOISON, hugetlb: isolate corrupted hugepage HWPOISON, hugetlb: maintain mce_bad_pages in handling hugepage error HWPOISON, hugetlb: set/clear PG_hwpoison bits on hugepage HWPOISON, hugetlb: enable error handling path for hugepage hugetlb, rmap: add reverse mapping for hugepage hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h Fix up trivial conflicts in mm/memory-failure.c
| * hugetlb: add missing unlock in avoidcopy path in hugetlb_cow()Naoya Horiguchi2010-08-111-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes possible deadlock in hugepage lock_page() by adding missing unlock_page(). libhugetlbfs test will hit this bug when the next patch in this patchset ("hugetlb, HWPOISON: move PG_HWPoison bit check") is applied. Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * hwpoison: rename CONFIGNaoya Horiguchi2010-08-111-2/+2
| | | | | | | | | | | | | | | | | | CONFIG_HUGETLBFS controls hugetlbfs interface code. OTOH, CONFIG_HUGETLB_PAGE controls hugepage management code. So we should use CONFIG_HUGETLB_PAGE here. Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: support hwpoison injection for hugepageNaoya Horiguchi2010-08-112-6/+11
| | | | | | | | | | | | | | | | | | | | | | | | This patch enables hwpoison injection through debug/hwpoison interfaces, with which we can test memory error handling for free or reserved hugepages (which cannot be tested by madvise() injector). [AK: Export PageHuge too for the injection module] Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: detect hwpoison in hugetlb codeNaoya Horiguchi2010-08-111-0/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch enables to block access to hwpoisoned hugepage and also enables to block unmapping for it. Dependency: "HWPOISON, hugetlb: enable error handling path for hugepage" Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: isolate corrupted hugepageNaoya Horiguchi2010-08-112-8/+36
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If error hugepage is not in-use, we can fully recovery from error by dequeuing it from freelist, so return RECOVERY. Otherwise whether or not we can recovery depends on user processes, so return DELAYED. Dependency: "HWPOISON, hugetlb: enable error handling path for hugepage" Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: maintain mce_bad_pages in handling hugepage errorNaoya Horiguchi2010-08-111-5/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | For now all pages in the error hugepage are considered as hwpoisoned, so count all of them in mce_bad_pages. Dependency: "HWPOISON, hugetlb: enable error handling path for hugepage" Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: set/clear PG_hwpoison bits on hugepageNaoya Horiguchi2010-08-111-0/+38
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To avoid race condition between concurrent memory errors on identified hugepage, we atomically test and set PG_hwpoison bit on the head page. All pages in the error hugepage are considered as hwpoisoned for now, so set and clear all PG_hwpoison bits in the hugepage with page lock of the head page held. Dependency: "HWPOISON, hugetlb: enable error handling path for hugepage" Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * HWPOISON, hugetlb: enable error handling path for hugepageNaoya Horiguchi2010-08-111-17/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch just enables handling path. Real containing and recovering operation will be implemented in following patches. Dependency: "hugetlb, rmap: add reverse mapping for hugepage." Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
| * hugetlb, rmap: add reverse mapping for hugepageNaoya Horiguchi2010-08-112-2/+101
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds reverse mapping feature for hugepage by introducing mapcount for shared/private-mapped hugepage and anon_vma for private-mapped hugepage. While hugepage is not currently swappable, reverse mapping can be useful for memory error handler. Without this patch, memory error handler cannot identify processes using the bad hugepage nor unmap it from them. That is: - for shared hugepage: we can collect processes using a hugepage through pagecache, but can not unmap the hugepage because of the lack of mapcount. - for privately mapped hugepage: we can neither collect processes nor unmap the hugepage. This patch solves these problems. This patch include the bug fix given by commit 23be7468e8, so reverts it. Dependency: "hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h" ChangeLog since May 24. - create hugetlb_inline.h and move is_vm_hugetlb_index() in it. - move functions setting up anon_vma for hugepage into mm/rmap.c. ChangeLog since May 13. - rebased to 2.6.34 - fix logic error (in case that private mapping and shared mapping coexist) - move is_vm_hugetlb_page() into include/linux/mm.h to use this function from linear_page_index() - define and use linear_hugepage_index() instead of compound_order() - use page_move_anon_rmap() in hugetlb_cow() - copy exclusive switch of __set_page_anon_rmap() into hugepage counterpart. - revert commit 24be7468 completely Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Acked-by: Fengguang Wu <fengguang.wu@intel.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andi Kleen <ak@linux.intel.com>
* | Merge branch 'stable/xen-swiotlb-0.8.6' of ↵Linus Torvalds2010-08-121-0/+4
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen * 'stable/xen-swiotlb-0.8.6' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen: x86: Detect whether we should use Xen SWIOTLB. pci-swiotlb-xen: Add glue code to setup dma_ops utilizing xen_swiotlb_* functions. swiotlb-xen: SWIOTLB library for Xen PV guest with PCI passthrough. xen/mmu: inhibit vmap aliases rather than trying to clear them out vmap: add flag to allow lazy unmap to be disabled at runtime xen: Add xen_create_contiguous_region xen: Rename the balloon lock xen: Allow unprivileged Xen domains to create iomap pages xen: use _PAGE_IOMAP in ioremap to do machine mappings Fix up trivial conflicts (adding both xen swiotlb and xen pci platform driver setup close to each other) in drivers/xen/{Kconfig,Makefile} and include/xen/xen-ops.h
| * | vmap: add flag to allow lazy unmap to be disabled at runtimeJeremy Fitzhardinge2010-07-271-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | Add a flag to force lazy_max_pages() to zero to prevent any outstanding mapped pages. We'll need this for Xen. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Nick Piggin <npiggin@suse.de>
* | | writeback: add comment to the dirty limit functionsWu Fengguang2010-08-121-3/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Document global_dirty_limits() and bdi_dirty_limit(). Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | writeback: avoid unnecessary calculation of bdi dirty thresholdsWu Fengguang2010-08-122-38/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Split get_dirty_limits() into global_dirty_limits()+bdi_dirty_limit(), so that the latter can be avoided when under global dirty background threshold (which is the normal state for most systems). Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | writeback: balance_dirty_pages(): reduce calls to global_page_stateWu Fengguang2010-08-121-62/+33
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Reducing the number of times balance_dirty_pages calls global_page_state reduces the cache references and so improves write performance on a variety of workloads. 'perf stats' of simple fio write tests shows the reduction in cache access. Where the test is fio 'write,mmap,600Mb,pre_read' on AMD AthlonX2 with 3Gb memory (dirty_threshold approx 600 Mb) running each test 10 times, dropping the fasted & slowest values then taking the average & standard deviation average (s.d.) in millions (10^6) 2.6.31-rc8 648.6 (14.6) +patch 620.1 (16.5) Achieving this reduction is by dropping clip_bdi_dirty_limit as it rereads the counters to apply the dirty_threshold and moving this check up into balance_dirty_pages where it has already read the counters. Also by rearrange the for loop to only contain one copy of the limit tests allows the pdflush test after the loop to use the local copies of the counters rather than rereading them. In the common case with no throttling it now calls global_page_state 5 fewer times and bdi_stat 2 fewer. Fengguang: This patch slightly changes behavior by replacing clip_bdi_dirty_limit() with the explicit check (nr_reclaimable + nr_writeback >= dirty_thresh) to avoid exceeding the dirty limit. Since the bdi dirty limit is mostly accurate we don't need to do routinely clip. A simple dirty limit check would be enough. The check is necessary because, in principle we should throttle everything calling balance_dirty_pages() when we're over the total limit, as said by Peter. We now set and clear dirty_exceeded not only based on bdi dirty limits, but also on the global dirty limit. The global limit check is added in place of clip_bdi_dirty_limit() for safety and not intended as a behavior change. The bdi limits should be tight enough to keep all dirty pages under the global limit at most time; occasional small exceeding should be OK though. The change makes the logic more obvious: the global limit is the ultimate goal and shall be always imposed. We may now start background writeback work based on outdated conditions. That's safe because the bdi flush thread will (and have to) double check the states. It reduces overall overheads because the test based on old states still have good chance to be right. [akpm@linux-foundation.org] fix uninitialized dirty_exceeded Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Jan Kara <jack@suse.cz> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: fix fatal kernel-doc errorRandy Dunlap2010-08-121-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fix a fatal kernel-doc error due to a #define coming between a function's kernel-doc notation and the function signature. (kernel-doc cannot handle this) Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: convert to use zone_to_nid() from bare zone->zone_pgdat->node_idKOSAKI Motohiro2010-08-111-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We have zone_to_nid(). this patch convert all existing users of zone->zone_pgdat->node_id. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Nishimura Daisuke <d-nishimura@mtf.biglobe.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: remove nid and zid argument from mem_cgroup_soft_limit_reclaim()KOSAKI Motohiro2010-08-112-8/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | mem_cgroup_soft_limit_reclaim() has zone, nid and zid argument. but nid and zid can be calculated from zone. So remove it. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Nishimura Daisuke <d-nishimura@mtf.biglobe.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: mem_cgroup_shrink_node_zone() doesn't need sc.nodemaskKOSAKI Motohiro2010-08-112-6/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently mem_cgroup_shrink_node_zone() call shrink_zone() directly. thus it doesn't need to initialize sc.nodemask because shrink_zone() doesn't use it at all. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Nishimura Daisuke <d-nishimura@mtf.biglobe.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: kill unnecessary initialization in mem_cgroup_shrink_node_zone()KOSAKI Motohiro2010-08-111-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | sc.nr_reclaimed and sc.nr_scanned have already been initialized few lines above "struct scan_control sc = {}" statement. So, This patch remove this unnecessary code. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Nishimura Daisuke <d-nishimura@mtf.biglobe.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: sc.nr_to_reclaim should be initializedKOSAKI Motohiro2010-08-111-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, mem_cgroup_shrink_node_zone() initialize sc.nr_to_reclaim as 0. It mean shrink_zone() only scan 32 pages and immediately return even if it doesn't reclaim any pages. This patch fixes it. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Nishimura Daisuke <d-nishimura@mtf.biglobe.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: avoid css_get()KAMEZAWA Hiroyuki2010-08-111-43/+76
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now, memory cgroup increments css(cgroup subsys state)'s reference count per a charged page. And the reference count is kept until the page is uncharged. But this has 2 bad effect. 1. Because css_get/put calls atomic_inc()/dec, heavy call of them on large smp will not scale well. 2. Because css's refcnt cannot be in a state as "ready-to-release", cgroup's notify_on_release handler can't work with memcg. 3. css's refcnt is atomic_t, it means smaller than 32bit. Maybe too small. This has been a problem since the 1st merge of memcg. This is a trial to remove css's refcnt per a page. Even if we remove refcnt, pre_destroy() does enough synchronization as - check res->usage == 0. - check no pages on LRU. This patch removes css's refcnt per page. Even after this patch, at the 1st look, it seems css_get() is still called in try_charge(). But the logic is. - If a memcg of mm->owner is cached one, consume_stock() will work. At success, return immediately. - If consume_stock returns false, css_get() is called and go to slow path which may be blocked. At the end of slow path, css_put() is called and restart from the start if necessary. So, in the fast path, we don't call css_get() and can avoid access to shared counter. This patch can make the most possible case fast. Here is a result of multi-threaded page fault benchmark. [Before] 25.32% multi-fault-all [kernel.kallsyms] [k] clear_page_c 9.30% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave 8.02% multi-fault-all [kernel.kallsyms] [k] try_get_mem_cgroup_from_mm <=====(*) 7.83% multi-fault-all [kernel.kallsyms] [k] down_read_trylock 5.38% multi-fault-all [kernel.kallsyms] [k] __css_put 5.29% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask 4.92% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq 4.24% multi-fault-all [kernel.kallsyms] [k] up_read 3.53% multi-fault-all [kernel.kallsyms] [k] css_put 2.11% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault 1.76% multi-fault-all [kernel.kallsyms] [k] __rmqueue 1.64% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge [After] 28.41% multi-fault-all [kernel.kallsyms] [k] clear_page_c 10.08% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq 9.58% multi-fault-all [kernel.kallsyms] [k] down_read_trylock 9.38% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave 5.86% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask 5.65% multi-fault-all [kernel.kallsyms] [k] up_read 2.82% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault 2.64% multi-fault-all [kernel.kallsyms] [k] mem_cgroup_add_lru_list 2.48% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge Then, 8.02% of try_get_mem_cgroup_from_mm() disappears because this patch removes css_tryget() in it. (But yes, this is an extreme case.) Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: use find_lock_task_mm() in memory cgroups oomKAMEZAWA Hiroyuki2010-08-112-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the OOM killer scans task, it check a task is under memcg or not when it's called via memcg's context. But, as Oleg pointed out, a thread group leader may have NULL ->mm and task_in_mem_cgroup() may do wrong decision. We have to use find_lock_task_mm() in memcg as generic OOM-Killer does. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: remove mem from arg of charge_commonDaisuke Nishimura2010-08-111-9/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | mem_cgroup_charge_common() is always called with @mem = NULL, so it's meaningless. This patch removes it. Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: remove redundant codeDaisuke Nishimura2010-08-111-10/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - try_get_mem_cgroup_from_mm() calls rcu_read_lock/unlock by itself, so we don't have to call them in task_in_mem_cgroup(). - *mz is not used in __mem_cgroup_uncharge_common(). - we don't have to call lookup_page_cgroup() in mem_cgroup_end_migration() after we've cleared PCG_MIGRATION of @oldpage. - remove empty comment. - remove redundant empty line in mem_cgroup_cache_charge(). Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: clean up waiting move acctKAMEZAWA Hiroyuki2010-08-111-22/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now, for checking a memcg is under task-account-moving, we do css_tryget() against mc.to and mc.from. But this is just complicating things. This patch makes the check easier. This patch adds a spinlock to move_charge_struct and guard modification of mc.to and mc.from. By this, we don't have to think about complicated races arount this not-critical path. [balbir@linux.vnet.ibm.com: don't crash on a null memcg being passed] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | memcg: clean up try_charge main loopKAMEZAWA Hiroyuki2010-08-111-100/+148
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | mem_cgroup_try_charge() has a big loop in it and seems to be hard to read. Most of routines are for slow path. This patch moves codes out from the loop and make it clear what's done. Summary: - refactoring a function to detect a memcg is under acccount move or not. - refactoring a function to wait for the end of moving task acct. - refactoring a main loop('s slow path) as a function and make it clear why we retry or quit by return code. - add fatal_signal_pending() check for bypassing charge loops. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | Merge branch 'for-2.6.36' of git://git.kernel.dk/linux-2.6-blockLinus Torvalds2010-08-103-236/+216
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * 'for-2.6.36' of git://git.kernel.dk/linux-2.6-block: (149 commits) block: make sure that REQ_* types are seen even with CONFIG_BLOCK=n xen-blkfront: fix missing out label blkdev: fix blkdev_issue_zeroout return value block: update request stacking methods to support discards block: fix missing export of blk_types.h writeback: fix bad _bh spinlock nesting drbd: revert "delay probes", feature is being re-implemented differently drbd: Initialize all members of sync_conf to their defaults [Bugz 315] drbd: Disable delay probes for the upcomming release writeback: cleanup bdi_register writeback: add new tracepoints writeback: remove unnecessary init_timer call writeback: optimize periodic bdi thread wakeups writeback: prevent unnecessary bdi threads wakeups writeback: move bdi threads exiting logic to the forker thread writeback: restructure bdi forker loop a little writeback: move last_active to bdi writeback: do not remove bdi from bdi_list writeback: simplify bdi code a little writeback: do not lose wake-ups in bdi threads ... Fixed up pretty trivial conflicts in drivers/block/virtio_blk.c and drivers/scsi/scsi_error.c as per Jens.
| * | | writeback: fix bad _bh spinlock nestingJens Axboe2010-08-071-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fix a bug where a lock is _bh nested within another _bh lock, but forgets to use the _bh variant for unlock. Further more, it's not necessary to test _bh locks, the inner lock can just use spin_lock(). So fix up the bug by making that change. Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: cleanup bdi_registerArtem Bityutskiy2010-08-071-19/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch makes sure we first initialize everything and set the BDI_registered flag, and only after this we add the bdi to 'bdi_list'. Current code adds the bdi to the list too early, and as a result I the WARN(!test_bit(BDI_registered, &bdi->state) in bdi forker is triggered. Also, it is in general good practice to make things visible only when they are fully initialized. Also, this patch does few micro clean-ups: 1. Removes the 'exit' label which does not do anything, just returns. This allows to get rid of few braces and 'ret' variable and make the code smaller. 2. If 'kthread_run()' fails, remove the error code it returns, not hard-coded '-ENOMEM'. Theoretically, some day 'kthread_run()' can return something else. Also, in case of failure it is not necessary to set 'bdi->wb.task' to NULL. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: add new tracepointsArtem Bityutskiy2010-08-071-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add 2 new trace points to the periodic write-back wake up case, just like we do in the 'bdi_queue_work()' function. Namely, introduce: 1. trace_writeback_wake_thread(bdi) 2. trace_writeback_wake_forker_thread(bdi) The first event is triggered every time we wake up a bdi thread to start periodic background write-out. The second event is triggered only when the bdi thread does not exist and should be created by the forker thread. This patch was suggested by Dave Chinner and Christoph Hellwig. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: remove unnecessary init_timer callArtem Bityutskiy2010-08-071-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The 'setup_timer()' function also calls 'init_timer()', so the extra 'init_timer()' call is not needed. Indeed, 'setup_timer()' is basically 'init_timer()' plus callback function and data pointers initialization. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: optimize periodic bdi thread wakeupsArtem Bityutskiy2010-08-071-16/+57
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Whe the first inode for a bdi is marked dirty, we wake up the bdi thread which should take care of the periodic background write-out. However, the write-out will actually start only 'dirty_writeback_interval' centisecs later, so we can delay the wake-up. This change was requested by Nick Piggin who pointed out that if we delay the wake-up, we weed out 2 unnecessary contex switches, which matters because '__mark_inode_dirty()' is a hot-path function. This patch introduces a new function - 'bdi_wakeup_thread_delayed()', which sets up a timer to wake-up the bdi thread and returns. So the wake-up is delayed. We also delete the timer in bdi threads just before writing-back. And synchronously delete it when unregistering bdi. At the unregister point the bdi does not have any users, so no one can arm it again. Since now we take 'bdi->wb_lock' in the timer, which can execute in softirq context, we have to use 'spin_lock_bh()' for 'bdi->wb_lock'. This patch makes this change as well. This patch also moves the 'bdi_wb_init()' function down in the file to avoid forward-declaration of 'bdi_wakeup_thread_delayed()'. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: prevent unnecessary bdi threads wakeupsArtem Bityutskiy2010-08-071-3/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Finally, we can get rid of unnecessary wake-ups in bdi threads, which are very bad for battery-driven devices. There are two types of activities bdi threads do: 1. process bdi works from the 'bdi->work_list' 2. periodic write-back So there are 2 sources of wake-up events for bdi threads: 1. 'bdi_queue_work()' - submits bdi works 2. '__mark_inode_dirty()' - adds dirty I/O to bdi's The former already has bdi wake-up code. The latter does not, and this patch adds it. '__mark_inode_dirty()' is hot-path function, but this patch adds another 'spin_lock(&bdi->wb_lock)' there. However, it is taken only in rare cases when the bdi has no dirty inodes. So adding this spinlock should be fine and should not affect performance. This patch makes sure bdi threads and the forker thread do not wake-up if there is nothing to do. The forker thread will nevertheless wake up at least every 5 min. to check whether it has to kill a bdi thread. This can also be optimized, but is not worth it. This patch also tidies up the warning about unregistered bid, and turns it from an ugly crocodile to a simple 'WARN()' statement. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: move bdi threads exiting logic to the forker threadArtem Bityutskiy2010-08-071-11/+58
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, bdi threads can decide to exit if there were no useful activities for 5 minutes. However, this causes nasty races: we can easily oops in the 'bdi_queue_work()' if the bdi thread decides to exit while we are waking it up. And even if we do not oops, but the bdi tread exits immediately after we wake it up, we'd lose the wake-up event and have an unnecessary delay (up to 5 secs) in the bdi work processing. This patch makes the forker thread to be the central place which not only creates bdi threads, but also kills them if they were inactive long enough. This better design-wise. Another reason why this change was done is to prepare for the further changes which will prevent the bdi threads from waking up every 5 sec and wasting power. Indeed, when the task does not wake up periodically anymore, it won't be able to exit either. This patch also moves the the 'wake_up_bit()' call from the bdi thread to the forker thread as well. So now the forker thread sets the BDI_pending bit, then forks the task or kills it, then clears the bit and wakes up the waiting process. The only process which may wain on the bit is 'bdi_wb_shutdown()'. This function was changed as well - now it first removes the bdi from the 'bdi_list', then waits on the 'BDI_pending' bit. Once it wakes up, it is guaranteed that the forker thread won't race with it, because the bdi is not visible. Note, the forker thread sets the 'BDI_pending' bit under the 'bdi->wb_lock' which is essential for proper serialization. And additionally, when we change 'bdi->wb.task', we now take the 'bdi->work_lock', to make sure that we do not lose wake-ups which we otherwise would when raced with, say, 'bdi_queue_work()'. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: restructure bdi forker loop a littleArtem Bityutskiy2010-08-071-30/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch re-structures the bdi forker a little: 1. Add 'bdi_cap_flush_forker(bdi)' condition check to the bdi loop. The reason for this is that the forker thread can start _before_ the 'BDI_registered' flag is set (see 'bdi_register()'), so the WARN() statement will fire for the default bdi. I observed this warning at boot-up. 2. Introduce an enum 'action' and use "switch" statement in the outer loop. This is a preparation to the further patch which will teach the forker thread killing bdi threads, so we'll have another case in the "switch" statement. This change was suggested by Christoph Hellwig. This patch is just a small step towards the coming change where the forker thread will kill the bdi threads. It should simplify reviewing the following changes, which would otherwise be larger. This patch also amends comments a little. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: do not remove bdi from bdi_listArtem Bityutskiy2010-08-071-21/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The forker thread removes bdis from 'bdi_list' before forking the bdi thread. But this is wrong for at least 2 reasons. Reason #1: if we temporary remove a bdi from the list, we may miss works which would otherwise be given to us. Reason #2: this is racy; indeed, 'bdi_wb_shutdown()' expects that bdis are always in the 'bdi_list' (see 'bdi_remove_from_list()'), and when it races with the forker thread, it can shut down the bdi thread at the same time as the forker creates it. This patch makes sure the forker thread never removes bdis from 'bdi_list' (which was suggested by Christoph Hellwig). In order to make sure that we do not race with 'bdi_wb_shutdown()', we have to hold the 'bdi_lock' while walking the 'bdi_list' and setting the 'BDI_pending' flag. NOTE! The error path is interesting. Currently, when we fail to create a bdi thread, we move the bdi to the tail of 'bdi_list'. But if we never remove the bdi from the list, we cannot move it to the tail either, because then we can mess up the RCU readers which walk the list. And also, we'll have the race described above in "Reason #2". But I not think that adding to the tail is any important so I just do not do that. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: simplify bdi code a littleArtem Bityutskiy2010-08-071-64/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch simplifies bdi code a little by removing the 'pending_list' which is redundant. Indeed, currently the forker thread ('bdi_forker_thread()') is working like this: 1. In a loop, fetch all bdi's which have works but have no writeback thread and move them to the 'pending_list'. 2. If the list is empty, sleep for 5 sec. 3. Otherwise, take one bdi from the list, fork the writeback thread for this bdi, and repeat the loop. IOW, it first moves everything to the 'pending_list', then process only one element, and so on. This patch simplifies the algorithm, which is now as follows. 1. Find the first bdi which has a work and remove it from the global list of bdi's (bdi_list). 2. If there was not such bdi, sleep 5 sec. 3. Fork the writeback thread for this bdi and repeat the loop. IOW, now we find the first bdi to process, process it, and so on. This is simpler and involves less lists. The bonus now is that we can get rid of a couple of functions, as well as remove complications which involve 'rcu_call()' and 'bdi->rcu_head'. This patch also makes sure we use 'list_add_tail_rcu()', instead of plain 'list_add_tail()', but this piece of code is going to be removed in the next patch anyway. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: do not lose wake-ups in the forker thread - 2Artem Bityutskiy2010-08-071-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, if someone submits jobs for the default bdi, we can lose wake-up events. E.g., this can happen if 'bdi_queue_work()' is called when 'bdi_forker_thread()' is executing code after 'wb_do_writeback(me, 0)', but before 'set_current_state(TASK_INTERRUPTIBLE)'. This situation is unlikely, and the result is not very severe - we'll just delay the execution of the work, but this is still not very nice. This patch fixes the issue by checking whether the default bdi has works before the forker thread goes sleep. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: do not lose wake-ups in the forker thread - 1Artem Bityutskiy2010-08-071-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the forker thread can lose wake-ups which may lead to unnecessary delays in processing bdi works. E.g., consider the following scenario. 1. 'bdi_forker_thread()' walks the 'bdi_list', finds out there is nothing to do, and is about to finish the loop. 2. A bdi thread decides to exit because it was inactive for long time. 3. 'bdi_queue_work()' adds a work to the bdi which just exited, so it wakes up the forker thread. 4. but 'bdi_forker_thread()' executes 'set_current_state(TASK_INTERRUPTIBLE)' and goes sleep. We lose a wake-up. Losing the wake-up is not fatal, but this means that the bdi work processing will be delayed by up to 5 sec. This race is theoretical, I never hit it, but it is worth fixing. The fix is to execute 'set_current_state(TASK_INTERRUPTIBLE)' _before_ walking 'bdi_list', not after. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: fix possible race when creating bdi threadsArtem Bityutskiy2010-08-071-17/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes a very unlikely race condition on the bdi forker thread error path: when bdi thread creation fails, 'bdi->wb.task' may contain the error code for a short period of time. If at the same time someone submits a work to this bdi, we can end up with an oops 'bdi_queue_work()' while executing 'wake_up_process(wb->task)'. This patch fixes the issue by introducing a temporary variable 'task' and storing the possible error code there, so that 'wb->task' would never take erroneous values. Note, this race is very unlikely and I never hit it, so it is theoretical, but nevertheless worth fixing. This patch also merges 2 comments which were previously separate. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: harmonize writeback threads namingArtem Bityutskiy2010-08-071-13/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The write-back code mixes words "thread" and "task" for the same things. This is not a big deal, but still an inconsistency. hch: a convention I tend to use and I've seen in various places is to always use _task for the storage of the task_struct pointer, and thread everywhere else. This especially helps with having foo_thread for the actual thread and foo_task for a global variable keeping the task_struct pointer This patch renames: * 'bdi_add_default_flusher_task()' -> 'bdi_add_default_flusher_thread()' * 'bdi_forker_task()' -> 'bdi_forker_thread()' because bdi threads are 'bdi_writeback_thread()', so these names are more consistent. This patch also amends commentaries and makes them refer the forker and bdi threads as "thread", not "task". Also, while on it, make 'bdi_add_default_flusher_thread()' declaration use 'static void' instead of 'void static' and make checkpatch.pl happy. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | | writeback: Add tracing to write_cache_pagesDave Chinner2010-08-071-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add a trace event to the ->writepage loop in write_cache_pages to give visibility into how the ->writepage call is changing variables within the writeback control structure. Of most interest is how wbc->nr_to_write changes from call to call, especially with filesystems that write multiple pages in ->writepage. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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