| Message ID | 20231218153553.807799-10-hch@lst.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [01/17] writeback: fix done_index when hitting the wbc->nr_to_write | expand |
On Mon 18-12-23 16:35:45, Christoph Hellwig wrote: > From: "Matthew Wilcox (Oracle)" <willy@infradead.org> > > 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. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > [hch: updated the commit log based on feedback from Jan Kara] > Signed-off-by: Christoph Hellwig <hch@lst.de> Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > mm/page-writeback.c | 94 ++++++++++++++++++++++----------------------- > 1 file changed, 46 insertions(+), 48 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 2a004c0b9bdfbf..c7983ea3040be4 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -2473,6 +2473,7 @@ int write_cache_pages(struct address_space *mapping, > { > int error; > pgoff_t end; /* Inclusive */ > + int i = 0; > > if (wbc->range_cyclic) { > wbc->index = mapping->writeback_index; /* prev offset */ > @@ -2487,63 +2488,60 @@ int write_cache_pages(struct address_space *mapping, > folio_batch_init(&wbc->fbatch); > wbc->err = 0; > > - while (wbc->index <= end) { > - int i; > - > - writeback_get_batch(mapping, wbc); > + for (;;) { > + struct folio *folio; > + unsigned long nr; > > + 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++) { > - struct folio *folio = wbc->fbatch.folios[i]; > - unsigned long nr; > + folio = wbc->fbatch.folios[i++]; > > - folio_lock(folio); > - if (!should_writeback_folio(mapping, wbc, folio)) { > - folio_unlock(folio); > - continue; > - } > + folio_lock(folio); > + if (!should_writeback_folio(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); > - nr = folio_nr_pages(folio); > - wbc->nr_to_write -= nr; > + error = writepage(folio, wbc, data); > + nr = folio_nr_pages(folio); > + wbc->nr_to_write -= nr; > > - /* > - * Handle the legacy AOP_WRITEPAGE_ACTIVATE magic return > - * value. Eventually all instances should just unlock > - * the folio themselves and return 0; > - */ > - if (error == AOP_WRITEPAGE_ACTIVATE) { > - folio_unlock(folio); > - error = 0; > - } > - > - if (error && !wbc->err) > - wbc->err = error; > + /* > + * Handle the legacy AOP_WRITEPAGE_ACTIVATE magic return value. > + * Eventually all instances should just unlock the folio > + * themselves and return 0; > + */ > + if (error == AOP_WRITEPAGE_ACTIVATE) { > + folio_unlock(folio); > + error = 0; > + } > > - /* > - * For integrity sync we have to keep going until we > - * have written all the folios we tagged for writeback > - * prior to entering this loop, even if we run past > - * wbc->nr_to_write or encounter errors. This is > - * because the file system may still have state to clear > - * for each folio. We'll eventually return the first > - * error encountered. > - * > - * For background writeback just push done_index past > - * this folio so that we can just restart where we left > - * off and media errors won't choke writeout for the > - * entire file. > - */ > - if (wbc->sync_mode == WB_SYNC_NONE && > - (wbc->err || wbc->nr_to_write <= 0)) { > - writeback_finish(mapping, wbc, > - folio->index + nr); > - return error; > - } > + if (error && !wbc->err) > + wbc->err = error; > + > + /* > + * For integrity sync we have to keep going until we have > + * written all the folios we tagged for writeback prior to > + * entering this loop, even if we run past wbc->nr_to_write or > + * encounter errors. This is because the file system may still > + * have state to clear for each folio. We'll eventually return > + * the first error encountered. > + * > + * For background writeback just push done_index past this folio > + * so that we can just restart where we left off and media > + * errors won't choke writeout for the entire file. > + */ > + if (wbc->sync_mode == WB_SYNC_NONE && > + (wbc->err || wbc->nr_to_write <= 0)) { > + writeback_finish(mapping, wbc, folio->index + nr); > + return error; > } > } > > -- > 2.39.2 >
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 2a004c0b9bdfbf..c7983ea3040be4 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2473,6 +2473,7 @@ int write_cache_pages(struct address_space *mapping, { int error; pgoff_t end; /* Inclusive */ + int i = 0; if (wbc->range_cyclic) { wbc->index = mapping->writeback_index; /* prev offset */ @@ -2487,63 +2488,60 @@ int write_cache_pages(struct address_space *mapping, folio_batch_init(&wbc->fbatch); wbc->err = 0; - while (wbc->index <= end) { - int i; - - writeback_get_batch(mapping, wbc); + for (;;) { + struct folio *folio; + unsigned long nr; + 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++) { - struct folio *folio = wbc->fbatch.folios[i]; - unsigned long nr; + folio = wbc->fbatch.folios[i++]; - folio_lock(folio); - if (!should_writeback_folio(mapping, wbc, folio)) { - folio_unlock(folio); - continue; - } + folio_lock(folio); + if (!should_writeback_folio(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); - nr = folio_nr_pages(folio); - wbc->nr_to_write -= nr; + error = writepage(folio, wbc, data); + nr = folio_nr_pages(folio); + wbc->nr_to_write -= nr; - /* - * Handle the legacy AOP_WRITEPAGE_ACTIVATE magic return - * value. Eventually all instances should just unlock - * the folio themselves and return 0; - */ - if (error == AOP_WRITEPAGE_ACTIVATE) { - folio_unlock(folio); - error = 0; - } - - if (error && !wbc->err) - wbc->err = error; + /* + * Handle the legacy AOP_WRITEPAGE_ACTIVATE magic return value. + * Eventually all instances should just unlock the folio + * themselves and return 0; + */ + if (error == AOP_WRITEPAGE_ACTIVATE) { + folio_unlock(folio); + error = 0; + } - /* - * For integrity sync we have to keep going until we - * have written all the folios we tagged for writeback - * prior to entering this loop, even if we run past - * wbc->nr_to_write or encounter errors. This is - * because the file system may still have state to clear - * for each folio. We'll eventually return the first - * error encountered. - * - * For background writeback just push done_index past - * this folio so that we can just restart where we left - * off and media errors won't choke writeout for the - * entire file. - */ - if (wbc->sync_mode == WB_SYNC_NONE && - (wbc->err || wbc->nr_to_write <= 0)) { - writeback_finish(mapping, wbc, - folio->index + nr); - return error; - } + if (error && !wbc->err) + wbc->err = error; + + /* + * For integrity sync we have to keep going until we have + * written all the folios we tagged for writeback prior to + * entering this loop, even if we run past wbc->nr_to_write or + * encounter errors. This is because the file system may still + * have state to clear for each folio. We'll eventually return + * the first error encountered. + * + * For background writeback just push done_index past this folio + * so that we can just restart where we left off and media + * errors won't choke writeout for the entire file. + */ + if (wbc->sync_mode == WB_SYNC_NONE && + (wbc->err || wbc->nr_to_write <= 0)) { + writeback_finish(mapping, wbc, folio->index + nr); + return error; } }