kernel/linux.git/include/trace/events/writeback.h, branch v4.14.245

memcg: fix a crash in wb_workfn when a device disappears

2021-02-23T13:00:30+00:00

[ Upstream commit 68f23b89067fdf187763e75a56087550624fdbee ] Without memcg, there is a one-to-one mapping between the bdi and bdi_writeback structures. In this world, things are fairly straightforward; the first thing bdi_unregister() does is to shutdown the bdi_writeback structure (or wb), and part of that writeback ensures that no other work queued against the wb, and that the wb is fully drained. With memcg, however, there is a one-to-many relationship between the bdi and bdi_writeback structures; that is, there are multiple wb objects which can all point to a single bdi. There is a refcount which prevents the bdi object from being released (and hence, unregistered). So in theory, the bdi_unregister() *should* only get called once its refcount goes to zero (bdi_put will drop the refcount, and when it is zero, release_bdi gets called, which calls bdi_unregister). Unfortunately, del_gendisk() in block/gen_hd.c never got the memo about the Brave New memcg World, and calls bdi_unregister directly. It does this without informing the file system, or the memcg code, or anything else. This causes the root wb associated with the bdi to be unregistered, but none of the memcg-specific wb's are shutdown. So when one of these wb's are woken up to do delayed work, they try to dereference their wb->bdi->dev to fetch the device name, but unfortunately bdi->dev is now NULL, thanks to the bdi_unregister() called by del_gendisk(). As a result, *boom*. Fortunately, it looks like the rest of the writeback path is perfectly happy with bdi->dev and bdi->owner being NULL, so the simplest fix is to create a bdi_dev_name() function which can handle bdi->dev being NULL. This also allows us to bulletproof the writeback tracepoints to prevent them from dereferencing a NULL pointer and crashing the kernel if one is tracing with memcg's enabled, and an iSCSI device dies or a USB storage stick is pulled. The most common way of triggering this will be hotremoval of a device while writeback with memcg enabled is going on. It was triggering several times a day in a heavily loaded production environment. Google Bug Id: 145475544 Link: https://lore.kernel.org/r/20191227194829.150110-1-tytso@mit.edu Link: http://lkml.kernel.org/r/20191228005211.163952-1-tytso@mit.edu Signed-off-by: Theodore Ts'o Cc: Chris Mason Cc: Tejun Heo Cc: Jens Axboe Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

include/trace/events/writeback.h: fix -Wstringop-truncation warnings

2021-02-23T13:00:30+00:00

[ Upstream commit d1a445d3b86c9341ce7a0954c23be0edb5c9bec5 ] There are many of those warnings. In file included from ./arch/powerpc/include/asm/paca.h:15, from ./arch/powerpc/include/asm/current.h:13, from ./include/linux/thread_info.h:21, from ./include/asm-generic/preempt.h:5, from ./arch/powerpc/include/generated/asm/preempt.h:1, from ./include/linux/preempt.h:78, from ./include/linux/spinlock.h:51, from fs/fs-writeback.c:19: In function 'strncpy', inlined from 'perf_trace_writeback_page_template' at ./include/trace/events/writeback.h:56:1: ./include/linux/string.h:260:9: warning: '__builtin_strncpy' specified bound 32 equals destination size [-Wstringop-truncation] return __builtin_strncpy(p, q, size); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix it by using the new strscpy_pad() which was introduced in "lib/string: Add strscpy_pad() function" and will always be NUL-terminated instead of strncpy(). Also, change strlcpy() to use strscpy_pad() in this file for consistency. Link: http://lkml.kernel.org/r/1564075099-27750-1-git-send-email-cai@lca.pw Fixes: 455b2864686d ("writeback: Initial tracing support") Fixes: 028c2dd184c0 ("writeback: Add tracing to balance_dirty_pages") Fixes: e84d0a4f8e39 ("writeback: trace event writeback_queue_io") Fixes: b48c104d2211 ("writeback: trace event bdi_dirty_ratelimit") Fixes: cc1676d917f3 ("writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()") Fixes: 9fb0a7da0c52 ("writeback: add more tracepoints") Signed-off-by: Qian Cai Reviewed-by: Jan Kara Cc: Tobin C. Harding Cc: Steven Rostedt (VMware) Cc: Ingo Molnar Cc: Tejun Heo Cc: Dave Chinner Cc: Fengguang Wu Cc: Jens Axboe Cc: Joe Perches Cc: Kees Cook Cc: Jann Horn Cc: Jonathan Corbet Cc: Nitin Gote Cc: Rasmus Villemoes Cc: Stephen Kitt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

writeback: Drop I_DIRTY_TIME_EXPIRE

2021-01-30T12:31:17+00:00

commit 5fcd57505c002efc5823a7355e21f48dd02d5a51 upstream. The only use of I_DIRTY_TIME_EXPIRE is to detect in __writeback_single_inode() that inode got there because flush worker decided it's time to writeback the dirty inode time stamps (either because we are syncing or because of age). However we can detect this directly in __writeback_single_inode() and there's no need for the strange propagation with I_DIRTY_TIME_EXPIRE flag. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

writeback: Fix sync livelock due to b_dirty_time processing

2020-09-03T09:22:32+00:00

commit f9cae926f35e8230330f28c7b743ad088611a8de upstream. When we are processing writeback for sync(2), move_expired_inodes() didn't set any inode expiry value (older_than_this). This can result in writeback never completing if there's steady stream of inodes added to b_dirty_time list as writeback rechecks dirty lists after each writeback round whether there's more work to be done. Fix the problem by using sync(2) start time is inode expiry value when processing b_dirty_time list similarly as for ordinarily dirtied inodes. This requires some refactoring of older_than_this handling which simplifies the code noticeably as a bonus. Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option") CC: stable@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

kernfs: introduce kernfs_node_id

2017-07-29T15:00:03+00:00

inode number and generation can identify a kernfs node. We are going to export the identification by exportfs operations, so put ino and generation into a separate structure. It's convenient when later patches use the identification. Acked-by: Greg Kroah-Hartman Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

mm: vmscan: kick flushers when we encounter dirty pages on the LRU

2017-02-25T01:46:54+00:00

Memory pressure can put dirty pages at the end of the LRU without anybody running into dirty limits. Don't start writing individual pages from kswapd while the flushers might be asleep. Unlike the old direct reclaim flusher wakeup (removed in the next patch) that flushes the number of pages just scanned, this patch wakes the flushers for all outstanding dirty pages. That seemed to perform better in a synthetic test that pushes dirty pages to the end of the LRU and into reclaim, because we know LRU aging outstrips writeback already, and this way we give younger dirty pages a headstart rather than wait until reclaim runs into them as well. It also means less plugging and risk of exhausting the struct request pool from reclaim. There is a concern that this will cause temporary files that used to get dirtied and truncated before writeback to now get written to disk under memory pressure. If this turns out to be a real problem, we'll have to revisit this and tame the reclaim flusher wakeups. [hannes@cmpxchg.org: mention dirty expiration as a condition] Link: http://lkml.kernel.org/r/20170126174739.GA30636@cmpxchg.org Link: http://lkml.kernel.org/r/20170123181641.23938-3-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Minchan Kim Acked-by: Michal Hocko Acked-by: Mel Gorman Acked-by: Hillf Danton Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: move vmscan writes and file write accounting to the node

2016-07-28T23:07:41+00:00

As reclaim is now node-based, it follows that page write activity due to page reclaim should also be accounted for on the node. For consistency, also account page writes and page dirtying on a per-node basis. After this patch, there are a few remaining zone counters that may appear strange but are fine. NUMA stats are still per-zone as this is a user-space interface that tools consume. NR_MLOCK, NR_SLAB_*, NR_PAGETABLE, NR_KERNEL_STACK and NR_BOUNCE are all allocations that potentially pin low memory and cannot trivially be reclaimed on demand. This information is still useful for debugging a page allocation failure warning. Link: http://lkml.kernel.org/r/1467970510-21195-21-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Acked-by: Michal Hocko Cc: Hillf Danton Acked-by: Johannes Weiner Cc: Joonsoo Kim Cc: Minchan Kim Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: move most file-based accounting to the node

2016-07-28T23:07:41+00:00

There are now a number of accounting oddities such as mapped file pages being accounted for on the node while the total number of file pages are accounted on the zone. This can be coped with to some extent but it's confusing so this patch moves the relevant file-based accounted. Due to throttling logic in the page allocator for reliable OOM detection, it is still necessary to track dirty and writeback pages on a per-zone basis. [mgorman@techsingularity.net: fix NR_ZONE_WRITE_PENDING accounting] Link: http://lkml.kernel.org/r/1468404004-5085-5-git-send-email-mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1467970510-21195-20-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Acked-by: Michal Hocko Cc: Hillf Danton Acked-by: Johannes Weiner Cc: Joonsoo Kim Cc: Minchan Kim Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs/fs-writeback.c: inode writeback list tracking tracepoints

2016-07-26T23:19:19+00:00

The per-sb inode writeback list tracks inodes currently under writeback to facilitate efficient sync processing. In particular, it ensures that sync only needs to walk through a list of inodes that were cleaned by the sync. Add a couple tracepoints to help identify when inodes are added/removed to and from the writeback lists. Piggyback off of the writeback lazytime tracepoint template as it already tracks the relevant inode information. Link: http://lkml.kernel.org/r/1466594593-6757-3-git-send-email-bfoster@redhat.com Signed-off-by: Brian Foster Reviewed-by: Jan Kara Cc: Dave Chinner cc: Josef Bacik Cc: Holger Hoffstätte Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds