linux.git/mm/page-writeback.c, branch v6.9

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

2024-02-24T01:48:38+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Cc: Christian Brauner 
Cc: Dave Chinner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: add a writeback iterator

2024-02-24T01:48:37+00:00

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 = ;
	}

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 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Cc: Christian Brauner 
Cc: Dave Chinner 
Cc: David Howells 
Cc: "Matthew Wilcox (Oracle)" 
Signed-off-by: Andrew Morton

writeback: move the folio_prepare_writeback loop out of write_cache_pages()

2024-02-24T01:48:37+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: use the folio_batch queue iterator

2024-02-24T01:48:37+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: simplify the loops in write_cache_pages()

2024-02-24T01:48:36+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: factor writeback_get_batch() out of write_cache_pages()

2024-02-24T01:48:36+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: factor folio_prepare_writeback() out of write_cache_pages()

2024-02-24T01:48:36+00:00

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) 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Signed-off-by: Andrew Morton

writeback: rework the loop termination condition in write_cache_pages

2024-02-24T01:48:36+00:00

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 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Cc: Christian Brauner 
Cc: Dave Chinner 
Cc: David Howells 
Cc: "Matthew Wilcox (Oracle)" 
Signed-off-by: Andrew Morton

writeback: only update ->writeback_index for range_cyclic writeback

2024-02-24T01:48:36+00:00

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 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Cc: "Matthew Wilcox (Oracle)" 
Signed-off-by: Andrew Morton

writeback: also update wbc->nr_to_write on writeback failure

2024-02-24T01:48:35+00:00

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 
Reviewed-by: Brian Foster 
Reviewed-by: Jan Kara 
Acked-by: Dave Chinner 
Cc: Christian Brauner 
Cc: David Howells 
Cc: "Matthew Wilcox (Oracle)" 
Signed-off-by: Andrew Morton