BMC/Intel-BMC/linux.git/include/linux/backing-dev-defs.h, branch dev-5.14-intel

writeback, cgroup: release dying cgwbs by switching attached inodes

2021-06-29T17:53:48+00:00

Asynchronously try to release dying cgwbs by switching attached inodes to the nearest living ancestor wb. It helps to get rid of per-cgroup writeback structures themselves and of pinned memory and block cgroups, which are significantly larger structures (mostly due to large per-cpu statistics data). This prevents memory waste and helps to avoid different scalability problems caused by large piles of dying cgroups. Reuse the existing mechanism of inode switching used for foreign inode detection. To speed things up batch up to 115 inode switching in a single operation (the maximum number is selected so that the resulting struct inode_switch_wbs_context can fit into 1024 bytes). Because every switching consists of two steps divided by an RCU grace period, it would be too slow without batching. Please note that the whole batch counts as a single operation (when increasing/decreasing isw_nr_in_flight). This allows to keep umounting working (flush the switching queue), however prevents cleanups from consuming the whole switching quota and effectively blocking the frn switching. A cgwb cleanup operation can fail due to different reasons (e.g. not enough memory, the cgwb has an in-flight/pending io, an attached inode in a wrong state, etc). In this case the next scheduled cleanup will make a new attempt. An attempt is made each time a new cgwb is offlined (in other words a memcg and/or a blkcg is deleted by a user). In the future an additional attempt scheduled by a timer can be implemented. [guro@fb.com: replace open-coded "115" with arithmetic] Link: https://lkml.kernel.org/r/YMEcSBcq/VXMiPPO@carbon.dhcp.thefacebook.com [guro@fb.com: add smp_mb() to inode_prepare_wbs_switch()] Link: https://lkml.kernel.org/r/YMFa+guFw7OFjf3X@carbon.dhcp.thefacebook.com [willy@infradead.org: fix documentation] Link: https://lkml.kernel.org/r/20210615200242.1716568-2-willy@infradead.org Link: https://lkml.kernel.org/r/20210608230225.2078447-9-guro@fb.com Signed-off-by: Roman Gushchin Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Tejun Heo Acked-by: Dennis Zhou Reviewed-by: Jan Kara Cc: Alexander Viro Cc: Dave Chinner Cc: Jan Kara Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback, cgroup: support switching multiple inodes at once

2021-06-29T17:53:48+00:00

Currently only a single inode can be switched to another writeback structure at once. That means to switch an inode a separate inode_switch_wbs_context structure must be allocated, and a separate rcu callback and work must be scheduled. It's fine for the existing ad-hoc switching, which is not happening that often, but sub-optimal for massive switching required in order to release a writeback structure. To prepare for it, let's add a support for switching multiple inodes at once. Instead of containing a single inode pointer, inode_switch_wbs_context will contain a NULL-terminated array of inode pointers. inode_do_switch_wbs() will be called for each inode. To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's list_locks will be acquired and released only once altogether for all inodes. wb_wakeup() will be also be called only once. Instead of calling wb_put(old_wb) after each successful switch, wb_put_many() is introduced and used. Link: https://lkml.kernel.org/r/20210608230225.2078447-8-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Reviewed-by: Jan Kara Acked-by: Dennis Zhou Cc: Alexander Viro Cc: Dave Chinner Cc: Jan Kara Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback, cgroup: keep list of inodes attached to bdi_writeback

2021-06-29T17:53:48+00:00

Currently there is no way to iterate over inodes attached to a specific cgwb structure. It limits the ability to efficiently reclaim the writeback structure itself and associated memory and block cgroup structures without scanning all inodes belonging to a sb, which can be prohibitively expensive. While dirty/in-active-writeback an inode belongs to one of the bdi_writeback's io lists: b_dirty, b_io, b_more_io and b_dirty_time. Once cleaned up, it's removed from all io lists. So the inode->i_io_list can be reused to maintain the list of inodes, attached to a bdi_writeback structure. This patch introduces a new wb->b_attached list, which contains all inodes which were dirty at least once and are attached to the given cgwb. Inodes attached to the root bdi_writeback structures are never placed on such list. The following patch will use this list to try to release cgwbs structures more efficiently. Link: https://lkml.kernel.org/r/20210608230225.2078447-6-guro@fb.com Signed-off-by: Roman Gushchin Suggested-by: Jan Kara Reviewed-by: Jan Kara Acked-by: Tejun Heo Acked-by: Dennis Zhou Cc: Alexander Viro Cc: Dave Chinner Cc: Jan Kara Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback: remove bdi->congested_fn

2020-07-08T23:20:46+00:00

Except for pktdvd, the only places setting congested bits are file systems that allocate their own backing_dev_info structures. And pktdvd is a deprecated driver that isn't useful in stack setup either. So remove the dead congested_fn stacking infrastructure. Signed-off-by: Christoph Hellwig Acked-by: Song Liu Acked-by: David Sterba [axboe: fixup unused variables in bcache/request.c] Signed-off-by: Jens Axboe

writeback: remove struct bdi_writeback_congested

2020-07-08T23:05:53+00:00

We never set any congested bits in the group writeback instances of it. And for the simpler bdi-wide case a simple scalar field is all that that is needed. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

writeback: remove {set,clear}_wb_congested

2020-07-08T23:05:53+00:00

Just merge them into their only callers. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

bdi: remove the name field in struct backing_dev_info

2020-05-09T22:15:13+00:00

The name is only printed for a not registered bdi in writeback. Use the device name there as is more useful anyway for the unlike case that the warning triggers. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Greg Kroah-Hartman Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe

bdi: add a ->dev_name field to struct backing_dev_info

2020-05-09T22:07:57+00:00

Cache a copy of the name for the life time of the backing_dev_info structure so that we can reference it even after unregistering. Fixes: 68f23b89067f ("memcg: fix a crash in wb_workfn when a device disappears") Reported-by: Yufen Yu Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe

buffer: remove useless comment and WB_REASON_FREE_MORE_MEM, reason.

2020-04-18T03:38:11+00:00

free_more_memory func has been completely removed in commit bc48f001de12 ("buffer: eliminate the need to call free_more_memory() in __getblk_slow()") So comment and `WB_REASON_FREE_MORE_MEM` reason about free_more_memory are no longer needed. Fixes: bc48f001de12 ("buffer: eliminate the need to call free_more_memory() in __getblk_slow()") Reviewed-by: Jan Kara Signed-off-by: Zhiqiang Liu Signed-off-by: Jens Axboe

writeback, memcg: Implement foreign dirty flushing

2019-08-27T15:22:38+00:00

There's an inherent mismatch between memcg and writeback. The former trackes ownership per-page while the latter per-inode. This was a deliberate design decision because honoring per-page ownership in the writeback path is complicated, may lead to higher CPU and IO overheads and deemed unnecessary given that write-sharing an inode across different cgroups isn't a common use-case. Combined with inode majority-writer ownership switching, this works well enough in most cases but there are some pathological cases. For example, let's say there are two cgroups A and B which keep writing to different but confined parts of the same inode. B owns the inode and A's memory is limited far below B's. A's dirty ratio can rise enough to trigger balance_dirty_pages() sleeps but B's can be low enough to avoid triggering background writeback. A will be slowed down without a way to make writeback of the dirty pages happen. This patch implements foreign dirty recording and foreign mechanism so that when a memcg encounters a condition as above it can trigger flushes on bdi_writebacks which can clean its pages. Please see the comment on top of mem_cgroup_track_foreign_dirty_slowpath() for details. A reproducer follows. write-range.c:: #include #include #include #include #include static const char *usage = "write-range FILE START SIZE\n"; int main(int argc, char **argv) { int fd; unsigned long start, size, end, pos; char *endp; char buf[4096]; if (argc < 4) { fprintf(stderr, usage); return 1; } fd = open(argv[1], O_WRONLY); if (fd < 0) { perror("open"); return 1; } start = strtoul(argv[2], &endp, 0); if (*endp != '\0') { fprintf(stderr, usage); return 1; } size = strtoul(argv[3], &endp, 0); if (*endp != '\0') { fprintf(stderr, usage); return 1; } end = start + size; while (1) { for (pos = start; pos < end; ) { long bread, bwritten = 0; if (lseek(fd, pos, SEEK_SET) < 0) { perror("lseek"); return 1; } bread = read(0, buf, sizeof(buf) < end - pos ? sizeof(buf) : end - pos); if (bread < 0) { perror("read"); return 1; } if (bread == 0) return 0; while (bwritten < bread) { long this; this = write(fd, buf + bwritten, bread - bwritten); if (this < 0) { perror("write"); return 1; } bwritten += this; pos += bwritten; } } } } repro.sh:: #!/bin/bash set -e set -x sysctl -w vm.dirty_expire_centisecs=300000 sysctl -w vm.dirty_writeback_centisecs=300000 sysctl -w vm.dirtytime_expire_seconds=300000 echo 3 > /proc/sys/vm/drop_caches TEST=/sys/fs/cgroup/test A=$TEST/A B=$TEST/B mkdir -p $A $B echo "+memory +io" > $TEST/cgroup.subtree_control echo $((1<<30)) > $A/memory.high echo $((32<<30)) > $B/memory.high rm -f testfile touch testfile fallocate -l 4G testfile echo "Starting B" (echo $BASHPID > $B/cgroup.procs pv -q --rate-limit 70M < /dev/urandom | ./write-range testfile $((2<<30)) $((2<<30))) & echo "Waiting 10s to ensure B claims the testfile inode" sleep 5 sync sleep 5 sync echo "Starting A" (echo $BASHPID > $A/cgroup.procs pv < /dev/urandom | ./write-range testfile 0 $((2<<30))) v2: Added comments explaining why the specific intervals are being used. v3: Use 0 @nr when calling cgroup_writeback_by_id() to use best-effort flushing while avoding possible livelocks. v4: Use get_jiffies_64() and time_before/after64() instead of raw jiffies_64 and arthimetic comparisons as suggested by Jan. Reviewed-by: Jan Kara Signed-off-by: Tejun Heo Signed-off-by: Jens Axboe