BMC/Intel-BMC/linux.git/fs/buffer.c, branch v4.2

buffer: remove unusued 'ret' variable

2015-06-02T15:22:34+00:00

Merge hickup on my part, due to a clash between the writeback changes and the EOPNOTSUPP removal in _submit_bh(). Signed-off-by: Jens Axboe

writeback: implement foreign cgroup inode detection

2015-06-02T14:40:20+00:00

As concurrent write sharing of an inode is expected to be very rare and memcg only tracks page ownership on first-use basis severely confining the usefulness of such sharing, cgroup writeback tracks ownership per-inode. While the support for concurrent write sharing of an inode is deemed unnecessary, an inode being written to by different cgroups at different points in time is a lot more common, and, more importantly, charging only by first-use can too readily lead to grossly incorrect behaviors (single foreign page can lead to gigabytes of writeback to be incorrectly attributed). To resolve this issue, cgroup writeback detects the majority dirtier of an inode and will transfer the ownership to it. To avoid unnnecessary oscillation, the detection mechanism keeps track of history and gives out the switch verdict only if the foreign usage pattern is stable over a certain amount of time and/or writeback attempts. The detection mechanism has fairly low space and computation overhead. It adds 8 bytes to struct inode (one int and two u16's) and minimal amount of calculation per IO. The detection mechanism converges to the correct answer usually in several seconds of IO time when there's a clear majority dirtier. Even when there isn't, it can reach an acceptable answer fairly quickly under most circumstances. Please see wb_detach_inode() for more details. This patch only implements detection. Following patches will implement actual switching. v2: wbc_account_io() now checks whether the wbc is associated with a wb before dereferencing it. This can happen when pageout() is writing pages directly without going through the usual writeback path. As pageout() path is single-threaded, we don't want it to be blocked behind a slow cgroup and ultimately want it to delegate actual writing to the usual writeback path. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen Signed-off-by: Jens Axboe

writeback: make writeback_control track the inode being written back

2015-06-02T14:39:48+00:00

Currently, for cgroup writeback, the IO submission paths directly associate the bio's with the blkcg from inode_to_wb_blkcg_css(); however, it'd be necessary to keep more writeback context to implement foreign inode writeback detection. wbc (writeback_control) is the natural fit for the extra context - it persists throughout the writeback of each inode and is passed all the way down to IO submission paths. This patch adds wbc_attach_and_unlock_inode(), wbc_detach_inode(), and wbc_attach_fdatawrite_inode() which are used to associate wbc with the inode being written back. IO submission paths now use wbc_init_bio() instead of directly associating bio's with blkcg themselves. This leaves inode_to_wb_blkcg_css() w/o any user. The function is removed. wbc currently only tracks the associated wb (bdi_writeback). Future patches will add more for foreign inode detection. The association is established under i_lock which will be depended upon when migrating foreign inodes to other wb's. As currently, once established, inode to wb association never changes, going through wbc when initializing bio's doesn't cause any behavior changes. v2: submit_blk_blkcg() now checks whether the wbc is associated with a wb before dereferencing it. This can happen when pageout() is writing pages directly without going through the usual writeback path. As pageout() path is single-threaded, we don't want it to be blocked behind a slow cgroup and ultimately want it to delegate actual writing to the usual writeback path. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen Signed-off-by: Jens Axboe

buffer, writeback: make __block_write_full_page() honor cgroup writeback

2015-06-02T14:37:23+00:00

[__]block_write_full_page() is used to implement ->writepage in various filesystems. All writeback logic is now updated to handle cgroup writeback and the block cgroup to issue IOs for is encoded in writeback_control and can be retrieved from the inode; however, [__]block_write_full_page() currently ignores the blkcg indicated by inode and issues all bio's without explicit blkcg association. This patch adds submit_bh_blkcg() which associates the bio with the specified blkio cgroup before issuing and uses it in __block_write_full_page() so that the issued bio's are associated with inode_to_wb_blkcg_css(inode). v2: Updated for per-inode wb association. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Andrew Morton Signed-off-by: Jens Axboe

memcg: add per cgroup dirty page accounting

2015-06-02T14:33:33+00:00

When modifying PG_Dirty on cached file pages, update the new MEM_CGROUP_STAT_DIRTY counter. This is done in the same places where global NR_FILE_DIRTY is managed. The new memcg stat is visible in the per memcg memory.stat cgroupfs file. The most recent past attempt at this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632 The new accounting supports future efforts to add per cgroup dirty page throttling and writeback. It also helps an administrator break down a container's memory usage and provides evidence to understand memcg oom kills (the new dirty count is included in memcg oom kill messages). The ability to move page accounting between memcg (memory.move_charge_at_immigrate) makes this accounting more complicated than the global counter. The existing mem_cgroup_{begin,end}_page_stat() lock is used to serialize move accounting with stat updates. Typical update operation: memcg = mem_cgroup_begin_page_stat(page) if (TestSetPageDirty()) { [...] mem_cgroup_update_page_stat(memcg) } mem_cgroup_end_page_stat(memcg) Summary of mem_cgroup_end_page_stat() overhead: - Without CONFIG_MEMCG it's a no-op - With CONFIG_MEMCG and no inter memcg task movement, it's just rcu_read_lock() - With CONFIG_MEMCG and inter memcg task movement, it's rcu_read_lock() + spin_lock_irqsave() A memcg parameter is added to several routines because their callers now grab mem_cgroup_begin_page_stat() which returns the memcg later needed by for mem_cgroup_update_page_stat(). Because mem_cgroup_begin_page_stat() may disable interrupts, some adjustments are needed: - move __mark_inode_dirty() from __set_page_dirty() to its caller. __mark_inode_dirty() locking does not want interrupts disabled. - use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in __delete_from_page_cache(), replace_page_cache_page(), invalidate_complete_page2(), and __remove_mapping(). text data bss dec hex filename 8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before 8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after +192 text bytes 8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before 8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after +773 text bytes Performance tests run on v4.0-rc1-36-g4f671fe2f952. Lower is better for all metrics, they're all wall clock or cycle counts. The read and write fault benchmarks just measure fault time, they do not include I/O time. * CONFIG_MEMCG not set: baseline patched kbuild 1m25.030000(+-0.088% 3 samples) 1m25.426667(+-0.120% 3 samples) dd write 100 MiB 0.859211561 +-15.10% 0.874162885 +-15.03% dd write 200 MiB 1.670653105 +-17.87% 1.669384764 +-11.99% dd write 1000 MiB 8.434691190 +-14.15% 8.474733215 +-14.77% read fault cycles 254.0(+-0.000% 10 samples) 253.0(+-0.000% 10 samples) write fault cycles 2021.2(+-3.070% 10 samples) 1984.5(+-1.036% 10 samples) * CONFIG_MEMCG=y root_memcg: baseline patched kbuild 1m25.716667(+-0.105% 3 samples) 1m25.686667(+-0.153% 3 samples) dd write 100 MiB 0.855650830 +-14.90% 0.887557919 +-14.90% dd write 200 MiB 1.688322953 +-12.72% 1.667682724 +-13.33% dd write 1000 MiB 8.418601605 +-14.30% 8.673532299 +-15.00% read fault cycles 266.0(+-0.000% 10 samples) 266.0(+-0.000% 10 samples) write fault cycles 2051.7(+-1.349% 10 samples) 2049.6(+-1.686% 10 samples) * CONFIG_MEMCG=y non-root_memcg: baseline patched kbuild 1m26.120000(+-0.273% 3 samples) 1m25.763333(+-0.127% 3 samples) dd write 100 MiB 0.861723964 +-15.25% 0.818129350 +-14.82% dd write 200 MiB 1.669887569 +-13.30% 1.698645885 +-13.27% dd write 1000 MiB 8.383191730 +-14.65% 8.351742280 +-14.52% read fault cycles 265.7(+-0.172% 10 samples) 267.0(+-0.000% 10 samples) write fault cycles 2070.6(+-1.512% 10 samples) 2084.4(+-2.148% 10 samples) As expected anon page faults are not affected by this patch. tj: Updated to apply on top of the recent cancel_dirty_page() changes. Signed-off-by: Sha Zhengju Signed-off-by: Greg Thelen Signed-off-by: Tejun Heo Signed-off-by: Jens Axboe

page_writeback: revive cancel_dirty_page() in a restricted form

2015-06-02T14:33:33+00:00

cancel_dirty_page() had some issues and b9ea25152e56 ("page_writeback: clean up mess around cancel_dirty_page()") replaced it with account_page_cleaned() which makes the caller responsible for clearing the dirty bit; unfortunately, the planned changes for cgroup writeback support requires synchronization between dirty bit manipulation and stat updates. While we can open-code such synchronization in each account_page_cleaned() callsite, that's gonna be unnecessarily awkward and verbose. This patch revives cancel_dirty_page() but in a more restricted form. All it does is TestClearPageDirty() followed by account_page_cleaned() invocation if the page was dirty. This helper covers all account_page_cleaned() usages except for __delete_from_page_cache() which is a special case anyway and left alone. As this leaves no module user for account_page_cleaned(), EXPORT_SYMBOL() is dropped from it. This patch just revives cancel_dirty_page() as a trivial wrapper to replace equivalent usages and doesn't introduce any functional changes. Signed-off-by: Tejun Heo Cc: Konstantin Khlebnikov Signed-off-by: Jens Axboe

block: fix returnvar.cocci warnings

2015-05-26T20:02:45+00:00

Remove unneeded variable used to store return value. Generated by: scripts/coccinelle/misc/returnvar.cocci Signed-off-by: Fengguang Wu Signed-off-by: Julia Lawall Signed-off-by: Jens Axboe

block: remove BIO_EOPNOTSUPP

2015-05-19T15:17:03+00:00

Since the big barrier rewrite/removal in 2007 we never fail FLUSH or FUA requests, which means we can remove the magic BIO_EOPNOTSUPP flag to help propagating those to the buffer_head layer. Signed-off-by: Christoph Hellwig Reviewed-by: Jeff Moyer Acked-by: Tejun Heo Signed-off-by: Jens Axboe

page_writeback: clean up mess around cancel_dirty_page()

2015-04-14T23:49:01+00:00

This patch replaces cancel_dirty_page() with a helper function account_page_cleaned() which only updates counters. It's called from truncate_complete_page() and from try_to_free_buffers() (hack for ext3). Page is locked in both cases, page-lock protects against concurrent dirtiers: see commit 2d6d7f982846 ("mm: protect set_page_dirty() from ongoing truncation"). Delete_from_page_cache() shouldn't be called for dirty pages, they must be handled by caller (either written or truncated). This patch treats final dirty accounting fixup at the end of __delete_from_page_cache() as a debug check and adds WARN_ON_ONCE() around it. If something removes dirty pages without proper handling that might be a bug and unwritten data might be lost. Hugetlbfs has no dirty pages accounting, ClearPageDirty() is enough here. cancel_dirty_page() in nfs_wb_page_cancel() is redundant. This is helper for nfs_invalidate_page() and it's called only in case complete invalidation. The mess was started in v2.6.20 after commits 46d2277c796f ("Clean up and make try_to_free_buffers() not race with dirty pages") and 3e67c0987d75 ("truncate: clear page dirtiness before running try_to_free_buffers()") first was reverted right in v2.6.20 in commit ecdfc9787fe5 ("Resurrect 'try_to_free_buffers()' VM hackery"), second in v2.6.25 commit a2b345642f53 ("Fix dirty page accounting leak with ext3 data=journal"). Custom fixes were introduced between these points. NFS in v2.6.23, commit 1b3b4a1a2deb ("NFS: Fix a write request leak in nfs_invalidate_page()"). Kludge in __delete_from_page_cache() in v2.6.24, commit 3a6927906f1b ("Do dirty page accounting when removing a page from the page cache"). Since v2.6.25 all of them are redundant. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Konstantin Khlebnikov Cc: Tejun Heo Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs: clarify rate limit suppressed buffer I/O errors

2014-10-21T19:55:11+00:00

When quiet_error applies rate limiting to buffer_io_error calls, what the they apply to is unclear because the name is so generic, particularly if the messages are interleaved with others: [ 1936.063572] quiet_error: 664293 callbacks suppressed [ 1936.065297] Buffer I/O error on dev sdr, logical block 257429952, lost async page write [ 1936.067814] Buffer I/O error on dev sdr, logical block 257429953, lost async page write Also, the function uses printk_ratelimit(), although printk.h includes a comment advising "Please don't use... Instead use printk_ratelimited()." Change buffer_io_error to check the BH_Quiet bit itself, drop the printk_ratelimit call, and print using printk_ratelimited. This makes the messages look like: [ 387.208839] buffer_io_error: 676394 callbacks suppressed [ 387.210693] Buffer I/O error on dev sdr, logical block 211291776, lost async page write [ 387.213432] Buffer I/O error on dev sdr, logical block 211291777, lost async page write Signed-off-by: Robert Elliott Reviewed-by: Webb Scales Signed-off-by: Jens Axboe