Subject: Re: linux-next: manual merge of the mm-stable tree with the cifs tree

From: David Howells <[email-masked]>
Date: Tue, 21 Feb 2023 14:39:24 +0000

Stephen Rothwell <[email-masked]> wrote:

> Andrew has already asked for it to be merged, so its up to Linus.
> 
> You could fetch it yourself and do a trial merge and send me your
> resolution ..
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm tags/mm-stable-2023-02-20-13-37

Okay, did that.  See attached.  Also here:

https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-cifs-mm

David
---
commit 71ad4f67439e60fe04bbf7aed8870e6f83a5d15e
Author: David Howells <[email-masked]>
Date:   Tue Feb 21 13:23:05 2023 +0000

    cifs: Handle transition to filemap_get_folios_tag()
    
    filemap_get_folios_tag() is being added and find_get_pages_range_tag() is
    being removed in effectively a single event.  This causes a problem for
    the:
    
        cifs: Change the I/O paths to use an iterator rather than a page list
    
    patch[1] on the cifs/for-next branch as it's adding a new user of the
    latter (which is going away), but can't yet be converted to using the
    former (which doesn't yet exist upstream).
    
    Here's a conversion patch that could be applied at merge time to deal with
    this.  The new cifs_writepages_region() is based directly on
    afs_writepages_region() and the AFS changes in the mm tree[2]:
    
        commit acc8d8588cb7e3e64b0d2fa611dad06574cd67b1
        Author: Vishal Moola (Oracle) <[email-masked]>
        afs: convert afs_writepages_region() to use filemap_get_folios_tag()
    
    can be replicated in cifs almost exactly.
    
    Signed-off-by: David Howells <[email-masked]>
    cc: Stephen Rothwell <[email-masked]>
    cc: Steve French <[email-masked]>
    cc: Shyam Prasad N <[email-masked]>
    cc: Rohith Surabattula <[email-masked]>
    cc: Tom Talpey <[email-masked]>
    cc: Paulo Alcantara <[email-masked]>
    cc: Jeff Layton <[email-masked]>
    cc: [email-masked]
    cc: Vishal Moola (Oracle) <[email-masked]>
    Link: https://lore.kernel.org/r/[email-masked]/ [1]
    Link: https://lore.kernel.org/r/[email-masked]/ [2]

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 58801d39213a..52af9cf93c65 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2856,78 +2856,85 @@ static int cifs_writepages_region(struct address_space *mapping,
 				  struct writeback_control *wbc,
 				  loff_t start, loff_t end, loff_t *_next)
 {
+	struct folio_batch fbatch;
 	struct folio *folio;
-	struct page *head_page;
+	unsigned int i;
 	ssize_t ret;
 	int n, skips = 0;
 
+	folio_batch_init(&fbatch);
+
 	do {
 		pgoff_t index = start / PAGE_SIZE;
 
-		n = find_get_pages_range_tag(mapping, &index, end / PAGE_SIZE,
-					     PAGECACHE_TAG_DIRTY, 1, &head_page);
+		n = filemap_get_folios_tag(mapping, &index, end / PAGE_SIZE,
+					   PAGECACHE_TAG_DIRTY, &fbatch);
 		if (!n)
 			break;
 
-		folio = page_folio(head_page);
-		start = folio_pos(folio); /* May regress with THPs */
+		for (i = 0; i < n; i++) {
+			folio = fbatch.folios[i];
+			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_put(folio);
-				return ret;
-			}
-		} else {
-			if (!folio_trylock(folio)) {
-				folio_put(folio);
-				return 0;
+			/* 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;
 			}
-		}
 
-		if (folio_mapping(folio) != mapping ||
-		    !folio_test_dirty(folio)) {
-			start += folio_size(folio);
-			folio_unlock(folio);
-			folio_put(folio);
-			continue;
-		}
+			if (folio->mapping != mapping ||
+			    !folio_test_dirty(folio)) {
+				start += folio_size(folio);
+				folio_unlock(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);
+			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_CIFS_FSCACHE
-				folio_wait_fscache(folio);
+					folio_wait_fscache(folio);
 #endif
-			} else {
-				start += folio_size(folio);
-			}
-			folio_put(folio);
-			if (wbc->sync_mode == WB_SYNC_NONE) {
-				if (skips >= 5 || need_resched())
-					break;
-				skips++;
+				} else {
+					start += folio_size(folio);
+				}
+				if (wbc->sync_mode == WB_SYNC_NONE) {
+					if (skips >= 5 || need_resched()) {
+						*_next = start;
+						return 0;
+					}
+					skips++;
+				}
+				continue;
 			}
-			continue;
-		}
 
-		if (!folio_clear_dirty_for_io(folio))
-			/* We hold the page lock - it should've been dirty. */
-			WARN_ON(1);
+			if (!folio_clear_dirty_for_io(folio))
+				/* We hold the page lock - it should've been dirty. */
+				WARN_ON(1);
 
-		ret = cifs_write_back_from_locked_folio(mapping, wbc, folio, start, end);
-		folio_put(folio);
-		if (ret < 0)
-			return ret;
+			ret = cifs_write_back_from_locked_folio(mapping, wbc,
+								folio, start, end);
+			if (ret < 0) {
+				folio_batch_release(&fbatch);
+				return ret;
+			}
+
+			start += ret;
+		}
 
-		start += ret;
+		folio_batch_release(&fbatch);
 		cond_resched();
 	} while (wbc->nr_to_write > 0);