lwn.git/mm/backing-dev.c, branch docs-5.15-2

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: 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

mm/backing-dev.c: use might_alloc()

2021-02-26T17:41:01+00:00

Now that my little helper has landed, use it more. On top of the existing check this also uses lockdep through the fs_reclaim annotations. [akpm@linux-foundation.org: include linux/sched/mm.h] Link: https://lkml.kernel.org/r/20210113135009.3606813-2-daniel.vetter@ffwll.ch Signed-off-by: Daniel Vetter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: backing-dev: Remove duplicated macro definition

2021-02-24T21:38:28+00:00

Move the K() macro a little forward to remove the same macro definition. Link: https://lkml.kernel.org/r/d1ccdf2d3116dce9814f2bcc1f0415ecb4c76ea5.1612862230.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm:backing-dev: use sysfs_emit in macro defining functions

2020-12-15T20:13:47+00:00

The cocci script used in commit bdacbb8d04f ("mm: Use sysfs_emit for struct kobject * uses") does not convert the name##_show macro because the macro uses concatenation via ##. Convert it by hand. Link: https://lkml.kernel.org/r/45ec6cfc177d743f9c0ebaf35e43969dce43af42.1605376435.git.joe@perches.com Signed-off-by: Joe Perches Cc: Christoph Lameter Cc: David Rientjes Cc: Greg Kroah-Hartman Cc: Hugh Dickins Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Mike Kravetz Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

bdi: replace BDI_CAP_NO_{WRITEBACK,ACCT_DIRTY} with a single flag

2020-09-24T19:43:39+00:00

Replace the two negative flags that are always used together with a single positive flag that indicates the writeback capability instead of two related non-capabilities. Also remove the pointless wrappers to just check the flag. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Johannes Thumshirn Signed-off-by: Jens Axboe

bdi: invert BDI_CAP_NO_ACCT_WB

2020-09-24T19:43:39+00:00

Replace BDI_CAP_NO_ACCT_WB with a positive BDI_CAP_WRITEBACK_ACCT to make the checks more obvious. Also remove the pointless bdi_cap_account_writeback wrapper that just obsfucates the check. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Johannes Thumshirn Signed-off-by: Jens Axboe

bdi: replace BDI_CAP_STABLE_WRITES with a queue and a sb flag

2020-09-24T19:43:39+00:00

The BDI_CAP_STABLE_WRITES is one of the few bits of information in the backing_dev_info shared between the block drivers and the writeback code. To help untangling the dependency replace it with a queue flag and a superblock flag derived from it. This also helps with the case of e.g. a file system requiring stable writes due to its own checksumming, but not forcing it on other users of the block device like the swap code. One downside is that we an't support the stable_pages_required bdi attribute in sysfs anymore. It is replaced with a queue attribute which also is writable for easier testing. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Johannes Thumshirn Signed-off-by: Jens Axboe

bdi: initialize ->ra_pages and ->io_pages in bdi_init

2020-09-24T19:43:39+00:00

Set up a readahead size by default, as very few users have a good reason to change it. This means code, ecryptfs, and orangefs now set up the values while they were previously missing it, while ubifs, mtd and vboxsf manually set it to 0 to avoid readahead. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Acked-by: David Sterba [btrfs] Acked-by: Richard Weinberger [ubifs, mtd] 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