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writeback: simplify the loops in write_cache_pages()

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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>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-02-15 07:36:44 +01:00 committed by Andrew Morton
parent 751e0d559c
commit 807d1fe360
1 changed files with 36 additions and 39 deletions
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75
mm/page-writeback.c
View file

@ -2454,6 +2454,7 @@ int write_cache_pages(struct address_space *mapping,
int error;
struct folio *folio;
pgoff_t end; /* Inclusive */
int i = 0;
if (wbc->range_cyclic) {
wbc->index = mapping->writeback_index; /* prev offset */
@ -2467,53 +2468,49 @@ int write_cache_pages(struct address_space *mapping,
folio_batch_init(&wbc->fbatch);
while (wbc->index <= end) {
int i;
writeback_get_batch(mapping, wbc);
for (;;) {
if (i == wbc->fbatch.nr) {
writeback_get_batch(mapping, wbc);
i = 0;
}
if (wbc->fbatch.nr == 0)
break;
for (i = 0; i < wbc->fbatch.nr; i++) {
folio = wbc->fbatch.folios[i];
folio = wbc->fbatch.folios[i++];
folio_lock(folio);
if (!folio_prepare_writeback(mapping, wbc, folio)) {
folio_unlock(folio);
continue;
}
folio_lock(folio);
if (!folio_prepare_writeback(mapping, wbc, folio)) {
folio_unlock(folio);
continue;
}
trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
error = writepage(folio, wbc, data);
wbc->nr_to_write -= folio_nr_pages(folio);
error = writepage(folio, wbc, data);
wbc->nr_to_write -= folio_nr_pages(folio);
if (error == AOP_WRITEPAGE_ACTIVATE) {
folio_unlock(folio);
error = 0;
}
if (error == AOP_WRITEPAGE_ACTIVATE) {
folio_unlock(folio);
error = 0;
}
/*
* For integrity writeback we have to keep going until
* we have written all the folios we tagged for
* writeback above, even if we run past wbc->nr_to_write
* or encounter errors.
* We stash away the first error we encounter in
* wbc->saved_err so that it can be retrieved when we're
* done. This is because the file system may still have
* state to clear for each folio.
*
* For background writeback we exit as soon as we run
* past wbc->nr_to_write or encounter the first error.
*/
if (wbc->sync_mode == WB_SYNC_ALL) {
if (error && !ret)
ret = error;
} else {
if (error || wbc->nr_to_write <= 0)
goto done;
}
/*
* For integrity writeback we have to keep going until we have
* written all the folios we tagged for writeback above, even if
* we run past wbc->nr_to_write or encounter errors.
* We stash away the first error we encounter in wbc->saved_err
* so that it can be retrieved when we're done. This is because
* the file system may still have state to clear for each folio.
*
* For background writeback we exit as soon as we run past
* wbc->nr_to_write or encounter the first error.
*/
if (wbc->sync_mode == WB_SYNC_ALL) {
if (error && !ret)
ret = error;
} else {
if (error || wbc->nr_to_write <= 0)
goto done;
}
}