FAILED: patch "[PATCH] ext4: write back partial-zeroed edges in WRITE_ZEROES" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x d19d239ada9b7c92d086a1f051b7566538ee0089
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026082453-darling-postcard-97fc@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d19d239ada9b7c92d086a1f051b7566538ee0089 Mon Sep 17 00:00:00 2001
From: Zhang Yi <[email protected]>
Date: Tue, 14 Jul 2026 16:00:43 +0800
Subject: [PATCH] ext4: write back partial-zeroed edges in WRITE_ZEROES

FALLOC_FL_WRITE_ZEROES requires that all blocks in the requested range end up as written extents with zeroed content. For unaligned edges that were partial-zeroed in dirty unwritten or delalloc state, the buffer is left dirty while the underlying extent may not yet be converted to written. As a result, a subsequent SYNC write to this range would still trigger metadata changes, which violates the semantics of WRITE_ZEROES.

Fix this by calling filemap_write_and_wait_range() for partial-zeroed edges to flush out the zeroed data and ensure the extent conversion is complete.

index d62fc4543760..d5f87a7f6c05 100644
@@ -4791,7 +4791,15 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	if (IS_ALIGNED(offset | end, blocksize))
 		return ret;
 
-	if (((file->f_flags & O_SYNC) || IS_SYNC(inode)) && partial_zeroed) {
+	/*
+	 * In FALLOC_FL_WRITE_ZEROES mode, edges that have been partially
+	 * zeroed must be written back to ensure the entire zeroed range
+	 * is converted to the written state. In SYNC mode, writeback is
+	 * also required to persist the zeroed data to disk.
+	 */
+	if (partial_zeroed &&
+	    ((mode & FALLOC_FL_WRITE_ZEROES) ||
+	     (file->f_flags & O_SYNC) || IS_SYNC(inode))) {
 		ret = filemap_write_and_wait_range(inode->i_mapping, offset,
 						   end - 1);
 		if (ret)