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