mm: remove stale comment __folio_mark_dirty

The __folio_mark_dirty will not mark inode dirty any longer. Remove the
stale comment of it.

Link: https://lkml.kernel.org/r/20240425131724.36778-5-shik

mm: remove stale comment __folio_mark_dirty

The __folio_mark_dirty will not mark inode dirty any longer. Remove the
stale comment of it.

Link: https://lkml.kernel.org/r/20240425131724.36778-5-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

mm: call __wb_calc_thresh instead of wb_calc_thresh in wb_over_bg_thresh

Call __wb_calc_thresh to calculate wb bg_thresh of gdtc in
wb_over_bg_thresh to remove unnecessary wrap in wb_calc_thresh.

L

mm: call __wb_calc_thresh instead of wb_calc_thresh in wb_over_bg_thresh

Call __wb_calc_thresh to calculate wb bg_thresh of gdtc in
wb_over_bg_thresh to remove unnecessary wrap in wb_calc_thresh.

Link: https://lkml.kernel.org/r/20240425131724.36778-4-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

mm: correct calculation of wb's bg_thresh in cgroup domain

wb_calc_thresh() is calculating wb's share of bg_thresh in the global
domain. However in case of cgroup writeback this is not the right
th

mm: correct calculation of wb's bg_thresh in cgroup domain

wb_calc_thresh() is calculating wb's share of bg_thresh in the global
domain. However in case of cgroup writeback this is not the right
thing to do. Consider the following domain hierarchy:

global domain (> 20G)
/ \
cgroup1 (10G) cgroup2 (10G)
| |
bdi wb1 wb2

and assume wb1 and wb2 have the same bandwidth and the background
threshold is set at 10%. The bg_thresh of cgroup1 and cgroup2 is going
to be 1G. Now because wb_calc_thresh(mdtc->wb, mdtc->bg_thresh)
calculates per-wb threshold in the global domain as (wb bandwidth) /
(domain bandwidth) it returns bg_thresh for wb1 as 0.5G although it has
nobody to compete against in cgroup1.

Fix the problem by calculating wb's share of bg_thresh in the cgroup
domain.

Test as following:
/* make it easier to observe the issue */
echo 300000 > /proc/sys/vm/dirty_expire_centisecs
echo 100 > /proc/sys/vm/dirty_writeback_centisecs

/* run fio in wb1 */
cd /sys/fs/cgroup
echo "+memory +io" > cgroup.subtree_control
mkdir group1
cd group1
echo 10G > memory.high
echo 10G > memory.max
echo $$ > cgroup.procs
mkfs.ext4 -F /dev/vdb
mount /dev/vdb /bdi1/
fio -name test -filename=/bdi1/file -size=600M -ioengine=libaio -bs=4K \
-iodepth=1 -rw=write -direct=0 --time_based -runtime=600 -invalidate=0

/* run fio in wb2 with a new shell */
cd /sys/fs/cgroup
mkdir group2
cd group2
echo 10G > memory.high
echo 10G > memory.max
echo $$ > cgroup.procs
mkfs.ext4 -F /dev/vdc
mount /dev/vdc /bdi2/
fio -name test -filename=/bdi2/file -size=600M -ioengine=libaio -bs=4K \
-iodepth=1 -rw=write -direct=0 --time_based -runtime=600 -invalidate=0

Before fix, the wrttien pages of wb1 and wb2 reported from
toos/writeback/wb_monitor.py keep growing. After fix, rare written pages
are accumulated.
There is no obvious change in fio result.

[jack@suse.cz: changelog rewording]
Link: https://lkml.kernel.org/r/20240425131724.36778-3-shikemeng@huaweicloud.com
Fixes: 74d369443325 ("writeback: Fix performance regression in wb_over_bg_thresh()")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

mm: enable __wb_calc_thresh to calculate dirty background threshold

Patch series "Fix and cleanups to page-writeback", v2.

This series contains some random cleanups and a fix to correct calculation

mm: enable __wb_calc_thresh to calculate dirty background threshold

Patch series "Fix and cleanups to page-writeback", v2.

This series contains some random cleanups and a fix to correct calculation
of wb's bg_thresh in cgroup domain. More details can be found respective
patches.


This patch (of 4):

Originally, __wb_calc_thresh always calculate wb's share of dirty
throttling threshold. By getting thresh of wb_domain from caller,
__wb_calc_thresh could be used for both dirty throttling and dirty
background threshold.

This is a preparation to correct threshold calculation of wb in cgroup.

Link: https://lkml.kernel.org/r/20240425131724.36778-1-shikemeng@huaweicloud.com
Link: https://lkml.kernel.org/r/20240425131724.36778-2-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: rename nr_reclaimable to nr_dirty in balance_dirty_pages

Commit 8d92890bd6b85 ("mm/writeback: discard NR_UNSTABLE_NFS, use
NR_WRITEBACK instead") removed NR_UNSTABLE_NFS and nr_reclaimabl

writeback: rename nr_reclaimable to nr_dirty in balance_dirty_pages

Commit 8d92890bd6b85 ("mm/writeback: discard NR_UNSTABLE_NFS, use
NR_WRITEBACK instead") removed NR_UNSTABLE_NFS and nr_reclaimable only
contains dirty page now. Rename nr_reclaimable to nr_dirty properly.

Link: https://lkml.kernel.org/r/20240423034643.141219-6-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Brian Foster <bfoster@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: support retrieving per group debug writeback stats of bdi

Add /sys/kernel/debug/bdi/xxx/wb_stats to show per group writeback stats
of bdi.

Following domain hierarchy is tested:

writeback: support retrieving per group debug writeback stats of bdi

Add /sys/kernel/debug/bdi/xxx/wb_stats to show per group writeback stats
of bdi.

Following domain hierarchy is tested:
global domain (320G)
/ \
cgroup domain1(10G) cgroup domain2(10G)
| |
bdi wb1 wb2

/* per wb writeback info of bdi is collected */
cat wb_stats
WbCgIno: 1
WbWriteback: 0 kB
WbReclaimable: 0 kB
WbDirtyThresh: 0 kB
WbDirtied: 0 kB
WbWritten: 0 kB
WbWriteBandwidth: 102400 kBps
b_dirty: 0
b_io: 0
b_more_io: 0
b_dirty_time: 0
state: 1

WbCgIno: 4091
WbWriteback: 1792 kB
WbReclaimable: 820512 kB
WbDirtyThresh: 6004692 kB
WbDirtied: 1820448 kB
WbWritten: 999488 kB
WbWriteBandwidth: 169020 kBps
b_dirty: 0
b_io: 0
b_more_io: 1
b_dirty_time: 0
state: 5

WbCgIno: 4131
WbWriteback: 1120 kB
WbReclaimable: 820064 kB
WbDirtyThresh: 6004728 kB
WbDirtied: 1822688 kB
WbWritten: 1002400 kB
WbWriteBandwidth: 153520 kBps
b_dirty: 0
b_io: 0
b_more_io: 1
b_dirty_time: 0
state: 5

[shikemeng@huaweicloud.com: fix build problems]
Link: https://lkml.kernel.org/r/20240423034643.141219-4-shikemeng@huaweicloud.com
Link: https://lkml.kernel.org/r/20240423034643.141219-3-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Brian Foster <bfoster@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

doc: improve the description of __folio_mark_dirty

Patch series "Improve buffer head documentation", v3.

Turn buffer head documentation into its own document, and make many
general improvements to

doc: improve the description of __folio_mark_dirty

Patch series "Improve buffer head documentation", v3.

Turn buffer head documentation into its own document, and make many
general improvements to the docs. Obviously there is much more that could
be done. Tested with make htmldocs.


This patch (of 8):

I've learned why it's safe to call __folio_mark_dirty() from
mark_buffer_dirty() without holding the folio lock, so update the
description to explain why.

Link: https://lkml.kernel.org/r/20240416031754.4076917-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240416031754.4076917-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

mm: Export writeback_iter()

Export writeback_iter() so that it can be used by netfslib as a module.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

mm: Export writeback_iter()

Export writeback_iter() so that it can be used by netfslib as a module.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-mm@kvack.org

show more ...

memory: remove the now superfluous sentinel element from ctl_table array

This commit comes at the tail end of a greater effort to remove the empty
elements at the end of the ctl_table arrays (sentin

memory: remove the now superfluous sentinel element from ctl_table array

This commit comes at the tail end of a greater effort to remove the empty
elements at the end of the ctl_table arrays (sentinels) which will reduce
the overall build time size of the kernel and run time memory bloat by ~64
bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Remove sentinel from all files under mm/ that register a sysctl table.

Link: https://lkml.kernel.org/r/20240328-jag-sysctl_remset_misc-v1-1-47c1463b3af2@samsung.com
Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: remove a use of write_cache_pages() from do_writepages()

Use the new writeback_iter() directly instead of indirecting through a
callback.

[hch@lst.de: ported to the while based iter styl

writeback: remove a use of write_cache_pages() from do_writepages()

Use the new writeback_iter() directly instead of indirecting through a
callback.

[hch@lst.de: ported to the while based iter style]
Link: https://lkml.kernel.org/r/20240215063649.2164017-15-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: add a writeback iterator

Refactor the code left in write_cache_pages into an iterator that the file
system can call to get the next folio for a writeback operation:

struct folio *folio

writeback: add a writeback iterator

Refactor the code left in write_cache_pages into an iterator that the file
system can call to get the next folio for a writeback operation:

struct folio *folio = NULL;

while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
error = <do per-folio writeback>;
}

The twist here is that the error value is passed by reference, so that the
iterator can restore it when breaking out of the loop.

Handling of the magic AOP_WRITEPAGE_ACTIVATE value stays outside the
iterator and needs is just kept in the write_cache_pages legacy wrapper.
in preparation for eventually killing it off.

Heavily based on a for_each* based iterator from Matthew Wilcox.

Link: https://lkml.kernel.org/r/20240215063649.2164017-14-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: move the folio_prepare_writeback loop out of write_cache_pages()

Move the loop for should-we-write-this-folio to writeback_get_folio.

[hch@lst.de: fold loop into existing helper instead

writeback: move the folio_prepare_writeback loop out of write_cache_pages()

Move the loop for should-we-write-this-folio to writeback_get_folio.

[hch@lst.de: fold loop into existing helper instead of a separate one per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-13-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: use the folio_batch queue iterator

Instead of keeping our own local iterator variable, use the one just added
to folio_batch.

Link: https://lkml.kernel.org/r/20240215063649.2164017-12-hc

writeback: use the folio_batch queue iterator

Instead of keeping our own local iterator variable, use the one just added
to folio_batch.

Link: https://lkml.kernel.org/r/20240215063649.2164017-12-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: simplify the loops in write_cache_pages()

Collapse the two nested loops into one. This is needed as a step towards
turning this into an iterator.

Note that this drops the "index <= end"

writeback: simplify the loops in write_cache_pages()

Collapse the two nested loops into one. This is needed as a step towards
turning this into an iterator.

Note that this drops the "index <= end" check in the previous outer loop
and just relies on filemap_get_folios_tag() to return 0 entries when index
> end. This actually has a subtle implication when end == -1 because then
the returned index will be -1 as well and thus if there is page present on
index -1, we could be looping indefinitely. But as the comment in
filemap_get_folios_tag documents this as already broken anyway we should
not worry about it here either. The fix for that would probably a change
to the filemap_get_folios_tag() calling convention.

[hch@lst.de: update the commit log per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-10-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: factor writeback_get_batch() out of write_cache_pages()

This simple helper will be the basis of the writeback iterator. To make
this work, we need to remember the current index and end p

writeback: factor writeback_get_batch() out of write_cache_pages()

This simple helper will be the basis of the writeback iterator. To make
this work, we need to remember the current index and end positions in
writeback_control.

[hch@lst.de: heavily rebased, add helpers to get the tag and end index, don't keep the end index in struct writeback_control]
Link: https://lkml.kernel.org/r/20240215063649.2164017-9-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: factor folio_prepare_writeback() out of write_cache_pages()

Reduce write_cache_pages() by about 30 lines; much of it is commentary,
but it all bundles nicely into an obvious function.

[h

writeback: factor folio_prepare_writeback() out of write_cache_pages()

Reduce write_cache_pages() by about 30 lines; much of it is commentary,
but it all bundles nicely into an obvious function.

[hch@lst.de: rename should_writeback_folio to folio_prepare_writeback per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-8-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: rework the loop termination condition in write_cache_pages

Rework the way we deal with the cleanup after the writepage call.

First handle the magic AOP_WRITEPAGE_ACTIVATE separately from

writeback: rework the loop termination condition in write_cache_pages

Rework the way we deal with the cleanup after the writepage call.

First handle the magic AOP_WRITEPAGE_ACTIVATE separately from real error
returns to get it out of the way of the actual error handling path.

The split the handling on intgrity vs non-integrity branches first, and
return early using a goto for the non-ingegrity early loop condition to
remove the need for the done and done_index local variables, and for
assigning the error to ret when we can just return error directly.

Link: https://lkml.kernel.org/r/20240215063649.2164017-7-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: only update ->writeback_index for range_cyclic writeback

mapping->writeback_index is only [1] used as the starting point for
range_cyclic writeback, so there is no point in updating it fo

writeback: only update ->writeback_index for range_cyclic writeback

mapping->writeback_index is only [1] used as the starting point for
range_cyclic writeback, so there is no point in updating it for other
types of writeback.

[1] except for btrfs_defrag_file which does really odd things with
mapping->writeback_index. But btrfs doesn't use write_cache_pages at all,
so this isn't relevant here.

Link: https://lkml.kernel.org/r/20240215063649.2164017-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: also update wbc->nr_to_write on writeback failure

When exiting write_cache_pages early due to a non-integrity write failure,
wbc->nr_to_write currently doesn't account for the folio we ju

writeback: also update wbc->nr_to_write on writeback failure

When exiting write_cache_pages early due to a non-integrity write failure,
wbc->nr_to_write currently doesn't account for the folio we just failed to
write. This doesn't matter because the callers always ingore the value on
a failure, but moving the update to common code will allow to simplify the
code, so do it.

Link: https://lkml.kernel.org/r/20240215063649.2164017-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

writeback: fix done_index when hitting the wbc->nr_to_write

When write_cache_pages finishes writing out a folio, it fails to update
done_index to account for the number of pages in the folio just wr

writeback: fix done_index when hitting the wbc->nr_to_write

When write_cache_pages finishes writing out a folio, it fails to update
done_index to account for the number of pages in the folio just written.
That means when range_cyclic writeback is restarted, it will be restarted
at this folio instead of after it as it should. Fix that by updating
done_index before breaking out of the loop.

Link: https://lkml.kernel.org/r/20240215063649.2164017-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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writeback: don't call mapping_set_error on AOP_WRITEPAGE_ACTIVATE

Patch series "convert write_cache_pages() to an iterator", v8.

This is an evolution of the series Matthew Wilcox originally sent in

writeback: don't call mapping_set_error on AOP_WRITEPAGE_ACTIVATE

Patch series "convert write_cache_pages() to an iterator", v8.

This is an evolution of the series Matthew Wilcox originally sent in June
2023, which has changed quite a bit since and now has a while based
iterator.


This patch (of 14):

mapping_set_error should only be called on 0 returns (which it ignores) or
a negative error code.

writepage_cb ends up being able to call writepage_cb on the magic
AOP_WRITEPAGE_ACTIVATE return value from ->writepage which means success
but the caller needs to unlock the page. Ignore that and just call
mapping_set_error on negative errors.

(no fixes tag as this goes back more than 20 years over various renames
and refactors so I've given up chasing down the original introduction)

Link: https://lkml.kernel.org/r/20240215063649.2164017-1-hch@lst.de
Link: https://lkml.kernel.org/r/20240215063649.2164017-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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blk-wbt: Fix detection of dirty-throttled tasks

The detection of dirty-throttled tasks in blk-wbt has been subtly broken
since its beginning in 2016. Namely if we are doing cgroup writeback and
the

blk-wbt: Fix detection of dirty-throttled tasks

The detection of dirty-throttled tasks in blk-wbt has been subtly broken
since its beginning in 2016. Namely if we are doing cgroup writeback and
the throttled task is not in the root cgroup, balance_dirty_pages() will
set dirty_sleep for the non-root bdi_writeback structure. However
blk-wbt checks dirty_sleep only in the root cgroup bdi_writeback
structure. Thus detection of recently throttled tasks is not working in
this case (we noticed this when we switched to cgroup v2 and suddently
writeback was slow).

Since blk-wbt has no easy way to get to proper bdi_writeback and
furthermore its intention has always been to work on the whole device
rather than on individual cgroups, just move the dirty_sleep timestamp
from bdi_writeback to backing_dev_info. That fixes the checking for
recently throttled task and saves memory for everybody as a bonus.

CC: stable@vger.kernel.org
Fixes: b57d74aff9ab ("writeback: track if we're sleeping on progress in balance_dirty_pages()")
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240123175826.21452-1-jack@suse.cz
[axboe: fixup indentation errors]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again

(struct dirty_throttle_control *)->thresh is an unsigned long, but is
passed as the u32 divisor argument to div_u64(). On archi

mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again

(struct dirty_throttle_control *)->thresh is an unsigned long, but is
passed as the u32 divisor argument to div_u64(). On architectures where
unsigned long is 64 bytes, the argument will be implicitly truncated.

Use div64_u64() instead of div_u64() so that the value used in the "is
this a safe division" check is the same as the divisor.

Also, remove redundant cast of the numerator to u64, as that should happen
implicitly.

This would be difficult to exploit in memcg domain, given the ratio-based
arithmetic domain_drity_limits() uses, but is much easier in global
writeback domain with a BDI_CAP_STRICTLIMIT-backing device, using e.g.
vm.dirty_bytes=(1<<32)*PAGE_SIZE so that dtc->thresh == (1<<32)

Link: https://lkml.kernel.org/r/20240118181954.1415197-1-zokeefe@google.com
Fixes: f6789593d5ce ("mm/page-writeback.c: fix divide by zero in bdi_dirty_limits()")
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Cc: Maxim Patlasov <MPatlasov@parallels.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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mm: fix arithmetic for max_prop_frac when setting max_ratio

Since now bdi->max_ratio is part per million, fix the wrong arithmetic for
max_prop_frac when setting max_ratio. Otherwise the miscalcula

mm: fix arithmetic for max_prop_frac when setting max_ratio

Since now bdi->max_ratio is part per million, fix the wrong arithmetic for
max_prop_frac when setting max_ratio. Otherwise the miscalculated
max_prop_frac will affect the incrementing of writeout completion count
when max_ratio is not 100%.

Link: https://lkml.kernel.org/r/20231219142508.86265-3-jefflexu@linux.alibaba.com
Fixes: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function")
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stefan Roesch <shr@devkernel.io>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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mm: fix arithmetic for bdi min_ratio

Since now bdi->min_ratio is part per million, fix the wrong arithmetic.
Otherwise it will fail with -EINVAL when setting a reasonable min_ratio,
as it tries to

mm: fix arithmetic for bdi min_ratio

Since now bdi->min_ratio is part per million, fix the wrong arithmetic.
Otherwise it will fail with -EINVAL when setting a reasonable min_ratio,
as it tries to set min_ratio to (min_ratio * BDI_RATIO_SCALE) in
percentage unit, which exceeds 100% anyway.

# cat /sys/class/bdi/253\:0/min_ratio
0
# cat /sys/class/bdi/253\:0/max_ratio
100
# echo 1 > /sys/class/bdi/253\:0/min_ratio
-bash: echo: write error: Invalid argument

Link: https://lkml.kernel.org/r/20231219142508.86265-2-jefflexu@linux.alibaba.com
Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function")
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stefan Roesch <shr@devkernel.io>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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