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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>
This commit is contained in:
Christoph Hellwig 2024-02-15 07:36:41 +01:00 committed by Andrew Morton
parent 5d899d43ed
commit f946e0d22e
1 changed files with 33 additions and 51 deletions
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84
mm/page-writeback.c
View File

@ -2396,13 +2396,12 @@ int write_cache_pages(struct address_space *mapping,
void *data)
{
int ret = 0;
int done = 0;
int error;
struct folio_batch fbatch;
struct folio *folio;
int nr_folios;
pgoff_t index;
pgoff_t end; /* Inclusive */
pgoff_t done_index;
xa_mark_t tag;
folio_batch_init(&fbatch);
@ -2419,8 +2418,7 @@ int write_cache_pages(struct address_space *mapping,
} else {
tag = PAGECACHE_TAG_DIRTY;
}
done_index = index;
while (!done && (index <= end)) {
while (index <= end) {
int i;
nr_folios = filemap_get_folios_tag(mapping, &index, end,
@ -2430,11 +2428,7 @@ int write_cache_pages(struct address_space *mapping,
break;
for (i = 0; i < nr_folios; i++) {
struct folio *folio = fbatch.folios[i];
unsigned long nr;
done_index = folio->index;
folio = fbatch.folios[i];
folio_lock(folio);
/*
@ -2469,45 +2463,32 @@ continue_unlock:
trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
error = writepage(folio, wbc, data);
nr = folio_nr_pages(folio);
wbc->nr_to_write -= nr;
if (unlikely(error)) {
/*
* Handle errors according to the type of
* writeback. There's no need to continue for
* background writeback. Just push done_index
* past this page so media errors won't choke
* writeout for the entire file. For integrity
* writeback, we must process the entire dirty
* set regardless of errors because the fs may
* still have state to clear for each page. In
* that case we continue processing and return
* the first error.
*/
if (error == AOP_WRITEPAGE_ACTIVATE) {
folio_unlock(folio);
error = 0;
} else if (wbc->sync_mode != WB_SYNC_ALL) {
ret = error;
done_index = folio->index + nr;
done = 1;
break;
}
if (!ret)
ret = error;
wbc->nr_to_write -= folio_nr_pages(folio);
if (error == AOP_WRITEPAGE_ACTIVATE) {
folio_unlock(folio);
error = 0;
}
/*
* We stop writing back only if we are not doing
* integrity sync. In case of integrity sync we have to
* keep going until we have written all the pages
* we tagged for writeback prior to entering this loop.
* 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.
*/
done_index = folio->index + nr;
if (wbc->nr_to_write <= 0 &&
wbc->sync_mode == WB_SYNC_NONE) {
done = 1;
break;
if (wbc->sync_mode == WB_SYNC_ALL) {
if (error && !ret)
ret = error;
} else {
if (error || wbc->nr_to_write <= 0)
goto done;
}
}
folio_batch_release(&fbatch);
@ -2524,14 +2505,15 @@ continue_unlock:
* of the file if we are called again, which can only happen due to
* -ENOMEM from the file system.
*/
if (wbc->range_cyclic) {
if (done)
mapping->writeback_index = done_index;
else
mapping->writeback_index = 0;
}
if (wbc->range_cyclic)
mapping->writeback_index = 0;
return ret;
done:
if (wbc->range_cyclic)
mapping->writeback_index = folio->index + folio_nr_pages(folio);
folio_batch_release(&fbatch);
return error;
}
EXPORT_SYMBOL(write_cache_pages);