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Message-ID: <522532.1677800499@warthog.procyon.org.uk>
Date: Thu, 02 Mar 2023 23:41:39 +0000
From: David Howells <dhowells@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Steve French <smfrench@...il.com>
Cc: dhowells@...hat.com, Vishal Moola <vishal.moola@...il.com>,
Shyam Prasad N <nspmangalore@...il.com>,
Rohith Surabattula <rohiths.msft@...il.com>,
Tom Talpey <tom@...pey.com>,
Stefan Metzmacher <metze@...ba.org>,
Paulo Alcantara <pc@....nz>, Jeff Layton <jlayton@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Marc Dionne <marc.dionne@...istor.com>,
linux-afs@...ts.infradead.org, linux-cifs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: cifs test patch to make cifs use its own version of write_cache_pages()
David Howells <dhowells@...hat.com> wrote:
> And then CIFS. ...
>
> Base + Own write_cache_pages():
> WRITE: bw=451MiB/s (473MB/s), 113MiB/s-113MiB/s (118MB/s-118MB/s)
> WRITE: bw=455MiB/s (478MB/s), 114MiB/s-114MiB/s (119MB/s-120MB/s)
> WRITE: bw=453MiB/s (475MB/s), 113MiB/s-113MiB/s (119MB/s-119MB/s)
> WRITE: bw=459MiB/s (481MB/s), 115MiB/s-115MiB/s (120MB/s-120MB/s)
Here's my patch to give cifs its own copy of write_cache_pages() so that the
function pointer can be eliminated in case some sort of spectre thing is
causing a slowdown.
This goes on top of "cifs test patch to convert to using write_cache_pages()".
David
---
fs/cifs/file.c | 137 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 136 insertions(+), 1 deletion(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 04e2466609d9..c33c7db729c7 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2802,6 +2802,141 @@ static int cifs_writepages_add_folio(struct folio *folio,
return 0;
}
+static int cifs_write_cache_pages(struct address_space *mapping,
+ struct writeback_control *wbc,
+ struct cifs_writepages_context *ctx)
+{
+ int ret = 0;
+ int done = 0;
+ int error;
+ struct folio_batch fbatch;
+ int nr_folios;
+ pgoff_t index;
+ pgoff_t end; /* Inclusive */
+ pgoff_t done_index;
+ int range_whole = 0;
+ xa_mark_t tag;
+
+ folio_batch_init(&fbatch);
+ if (wbc->range_cyclic) {
+ index = mapping->writeback_index; /* prev offset */
+ end = -1;
+ } else {
+ index = wbc->range_start >> PAGE_SHIFT;
+ end = wbc->range_end >> PAGE_SHIFT;
+ if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+ range_whole = 1;
+ }
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
+ tag_pages_for_writeback(mapping, index, end);
+ tag = PAGECACHE_TAG_TOWRITE;
+ } else {
+ tag = PAGECACHE_TAG_DIRTY;
+ }
+ done_index = index;
+ while (!done && (index <= end)) {
+ int i;
+
+ nr_folios = filemap_get_folios_tag(mapping, &index, end,
+ tag, &fbatch);
+
+ if (nr_folios == 0)
+ break;
+
+ for (i = 0; i < nr_folios; i++) {
+ struct folio *folio = fbatch.folios[i];
+
+ done_index = folio->index;
+
+ folio_lock(folio);
+
+ /*
+ * Page truncated or invalidated. We can freely skip it
+ * then, even for data integrity operations: the page
+ * has disappeared concurrently, so there could be no
+ * real expectation of this data integrity operation
+ * even if there is now a new, dirty page at the same
+ * pagecache address.
+ */
+ if (unlikely(folio->mapping != mapping)) {
+continue_unlock:
+ folio_unlock(folio);
+ continue;
+ }
+
+ if (!folio_test_dirty(folio)) {
+ /* someone wrote it for us */
+ goto continue_unlock;
+ }
+
+ if (folio_test_writeback(folio)) {
+ if (wbc->sync_mode != WB_SYNC_NONE)
+ folio_wait_writeback(folio);
+ else
+ goto continue_unlock;
+ }
+
+ BUG_ON(folio_test_writeback(folio));
+ if (!folio_clear_dirty_for_io(folio))
+ goto continue_unlock;
+
+ error = cifs_writepages_add_folio(folio, wbc, ctx);
+ 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 +
+ folio_nr_pages(folio);
+ done = 1;
+ break;
+ }
+ if (!ret)
+ ret = error;
+ }
+
+ /*
+ * 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.
+ */
+ if (--wbc->nr_to_write <= 0 &&
+ wbc->sync_mode == WB_SYNC_NONE) {
+ done = 1;
+ break;
+ }
+ }
+ folio_batch_release(&fbatch);
+ cond_resched();
+ }
+
+ /*
+ * If we hit the last page and there is more work to be done: wrap
+ * back the index back to the start of the file for the next
+ * time we are called.
+ */
+ if (wbc->range_cyclic && !done)
+ done_index = 0;
+ if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+ mapping->writeback_index = done_index;
+
+ return ret;
+}
+
/*
* Write some of the pending data back to the server
*/
@@ -2816,7 +2951,7 @@ static int cifs_writepages(struct address_space *mapping,
* to prevent it.
*/
- ret = write_cache_pages(mapping, wbc, cifs_writepages_add_folio, &ctx);
+ ret = cifs_write_cache_pages(mapping, wbc, &ctx);
if (ret >= 0 && ctx.begun) {
ret = cifs_writepages_submit(mapping, wbc, &ctx);
if (ret < 0)
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