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Message-Id: <20230302231638.521280-3-dhowells@redhat.com>
Date: Thu, 2 Mar 2023 23:16:37 +0000
From: David Howells <dhowells@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Steve French <smfrench@...il.com>
Cc: David Howells <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,
Steve French <sfrench@...ba.org>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: [PATCH 2/3] afs: Partially revert and use filemap_get_folio_tag()
Partially revert the changes made by:
acc8d8588cb7e3e64b0d2fa611dad06574cd67b1.
afs: convert afs_writepages_region() to use filemap_get_folios_tag()
The issue is that filemap_get_folios_tag() gets a batch of pages at a time,
and then afs_writepages_region() goes through them one at a time, extends
each into an operation with as many pages as will fit using the loop in
afs_extend_writeback() and submits it - but, in the common case, this means
that the other pages in the batch already got annexed and processed in
afs_extend_writeback() and we end up doing duplicate processing.
Switching to write_cache_pages() isn't an immediate substitute as that
doesn't take account of PG_fscache (and this bit is used in other ways by
other filesystems).
So go back to finding the next folio from the VM one at a time and then
extending the op onwards.
Fixes: acc8d8588cb7 ("afs: convert afs_writepages_region() to use filemap_get_folios_tag()")
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Linus Torvalds <torvalds@...ux-foundation.org>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: Steve French <sfrench@...ba.org>
cc: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
cc: Andrew Morton <akpm@...ux-foundation.org>
cc: linux-afs@...ts.infradead.org
cc: linux-mm@...ck.org
Link: https://lore.kernel.org/r/2214157.1677250083@warthog.procyon.org.uk/
---
fs/afs/write.c | 118 ++++++++++++++++++++++++-------------------------
1 file changed, 57 insertions(+), 61 deletions(-)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 571f3b9a417e..2ed76697be96 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -704,87 +704,83 @@ static int afs_writepages_region(struct address_space *mapping,
bool max_one_loop)
{
struct folio *folio;
- struct folio_batch fbatch;
ssize_t ret;
- unsigned int i;
- int n, skips = 0;
+ int skips = 0;
_enter("%llx,%llx,", start, end);
- folio_batch_init(&fbatch);
do {
pgoff_t index = start / PAGE_SIZE;
- n = filemap_get_folios_tag(mapping, &index, end / PAGE_SIZE,
- PAGECACHE_TAG_DIRTY, &fbatch);
-
- if (!n)
+ folio = filemap_get_folio_tag(mapping, &index, end / PAGE_SIZE,
+ PAGECACHE_TAG_DIRTY);
+ if (!folio)
break;
- for (i = 0; i < n; i++) {
- folio = fbatch.folios[i];
- start = folio_pos(folio); /* May regress with THPs */
- _debug("wback %lx", folio_index(folio));
+ start = folio_pos(folio); /* May regress with THPs */
- /* At this point we hold neither the i_pages lock nor the
- * page lock: the page may be truncated or invalidated
- * (changing page->mapping to NULL), or even swizzled
- * back from swapper_space to tmpfs file mapping
- */
- if (wbc->sync_mode != WB_SYNC_NONE) {
- ret = folio_lock_killable(folio);
- if (ret < 0) {
- folio_batch_release(&fbatch);
- return ret;
- }
- } else {
- if (!folio_trylock(folio))
- continue;
- }
+ _debug("wback %lx", folio_index(folio));
- if (folio->mapping != mapping ||
- !folio_test_dirty(folio)) {
- start += folio_size(folio);
- folio_unlock(folio);
- continue;
+ /* At this point we hold neither the i_pages lock nor the
+ * page lock: the page may be truncated or invalidated
+ * (changing page->mapping to NULL), or even swizzled
+ * back from swapper_space to tmpfs file mapping
+ */
+ if (wbc->sync_mode != WB_SYNC_NONE) {
+ ret = folio_lock_killable(folio);
+ if (ret < 0) {
+ folio_put(folio);
+ return ret;
+ }
+ } else {
+ if (!folio_trylock(folio)) {
+ folio_put(folio);
+ return 0;
}
+ }
- if (folio_test_writeback(folio) ||
- folio_test_fscache(folio)) {
- folio_unlock(folio);
- if (wbc->sync_mode != WB_SYNC_NONE) {
- folio_wait_writeback(folio);
+ if (folio_mapping(folio) != mapping ||
+ !folio_test_dirty(folio)) {
+ start += folio_size(folio);
+ folio_unlock(folio);
+ folio_put(folio);
+ continue;
+ }
+
+ if (folio_test_writeback(folio) ||
+ folio_test_fscache(folio)) {
+ folio_unlock(folio);
+ if (wbc->sync_mode != WB_SYNC_NONE) {
+ folio_wait_writeback(folio);
#ifdef CONFIG_AFS_FSCACHE
- folio_wait_fscache(folio);
+ folio_wait_fscache(folio);
#endif
- } else {
- start += folio_size(folio);
- }
- if (wbc->sync_mode == WB_SYNC_NONE) {
- if (skips >= 5 || need_resched()) {
- *_next = start;
- _leave(" = 0 [%llx]", *_next);
- return 0;
- }
- skips++;
- }
- continue;
+ } else {
+ start += folio_size(folio);
}
-
- if (!folio_clear_dirty_for_io(folio))
- BUG();
- ret = afs_write_back_from_locked_folio(mapping, wbc,
- folio, start, end);
- if (ret < 0) {
- _leave(" = %zd", ret);
- folio_batch_release(&fbatch);
- return ret;
+ folio_put(folio);
+ if (wbc->sync_mode == WB_SYNC_NONE) {
+ if (skips >= 5 || need_resched())
+ break;
+ skips++;
}
+ continue;
+ }
- start += ret;
+ if (!folio_clear_dirty_for_io(folio))
+ BUG();
+ ret = afs_write_back_from_locked_folio(mapping, wbc, folio, start, end);
+ folio_put(folio);
+ if (ret < 0) {
+ _leave(" = %zd", ret);
+ return ret;
}
- folio_batch_release(&fbatch);
+ start += ret;
+
+ if (max_one_loop)
+ break;
+
cond_resched();
} while (wbc->nr_to_write > 0);
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