Patch "ext4: pipeline buffer reads in mext_page_mkuptodate()" has been added to the 6.11-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ext4: pipeline buffer reads in mext_page_mkuptodate()

to the 6.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-pipeline-buffer-reads-in-mext_page_mkuptodate.patch
and it can be found in the queue-6.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 655354eea6bfc6df901a64c2d8246a7d6ef4f987
Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Date:   Thu Jul 18 23:30:00 2024 +0100

    ext4: pipeline buffer reads in mext_page_mkuptodate()
    
    [ Upstream commit 368a83cebbb949adbcc20877c35367178497d9cc ]
    
    Instead of synchronously reading one buffer at a time, submit reads
    as we walk the buffers in the first loop, then wait for them in the
    second loop.  This should be significantly more efficient, particularly
    on HDDs, but I have not measured.
    
    Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
    Link: https://patch.msgid.link/20240718223005.568869-2-willy@xxxxxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
    Stable-dep-of: 2f3d93e210b9 ("ext4: fix race in buffer_head read fault injection")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index c95e3e526390d..7a80c32fd7326 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -173,7 +173,9 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to)
 	sector_t block;
 	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
 	unsigned int blocksize, block_start, block_end;
-	int i, err,  nr = 0, partial = 0;
+	int i, nr = 0;
+	bool partial = false;
+
 	BUG_ON(!folio_test_locked(folio));
 	BUG_ON(folio_test_writeback(folio));
 
@@ -191,13 +193,13 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to)
 		block_end = block_start + blocksize;
 		if (block_end <= from || block_start >= to) {
 			if (!buffer_uptodate(bh))
-				partial = 1;
+				partial = true;
 			continue;
 		}
 		if (buffer_uptodate(bh))
 			continue;
 		if (!buffer_mapped(bh)) {
-			err = ext4_get_block(inode, block, bh, 0);
+			int err = ext4_get_block(inode, block, bh, 0);
 			if (err)
 				return err;
 			if (!buffer_mapped(bh)) {
@@ -206,6 +208,12 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to)
 				continue;
 			}
 		}
+		lock_buffer(bh);
+		if (buffer_uptodate(bh)) {
+			unlock_buffer(bh);
+			continue;
+		}
+		ext4_read_bh_nowait(bh, 0, NULL);
 		BUG_ON(nr >= MAX_BUF_PER_PAGE);
 		arr[nr++] = bh;
 	}
@@ -215,11 +223,10 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to)
 
 	for (i = 0; i < nr; i++) {
 		bh = arr[i];
-		if (!bh_uptodate_or_lock(bh)) {
-			err = ext4_read_bh(bh, 0, NULL);
-			if (err)
-				return err;
-		}
+		wait_on_buffer(bh);
+		if (buffer_uptodate(bh))
+			continue;
+		return -EIO;
 	}
 out:
 	if (!partial)