linux-ext4 - [PATCH 08/10] libext2fs: allow unix_write_byte when the write would be aligned

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Message-ID: <174787198211.1484572.66428039447930057.stgit@frogsfrogsfrogs>
Date: Wed, 21 May 2025 17:10:19 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: John@...ves.net, linux-ext4@...r.kernel.org, miklos@...redi.hu,
 joannelkoong@...il.com, bernd@...ernd.com, linux-fsdevel@...r.kernel.org
Subject: [PATCH 08/10] libext2fs: allow unix_write_byte when the write would
 be aligned

From: Darrick J. Wong <djwong@...nel.org>

If someone calls write_byte on an IO channel with an alignment
requirement and the range to be written is aligned correctly, go ahead
and do the write.  This will be needed later when we try to speed up
superblock writes.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 lib/ext2fs/unix_io.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index 4c924ec9ee0760..008a5b46ce7f1f 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -1534,7 +1534,9 @@ static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
 #ifdef ALIGN_DEBUG
 		printf("unix_write_byte: O_DIRECT fallback\n");
 #endif
-		return EXT2_ET_UNIMPLEMENTED;
+		if (!IS_ALIGNED(data->offset + offset, channel->align) ||
+		    !IS_ALIGNED(data->offset + offset + size, channel->align))
+			return EXT2_ET_UNIMPLEMENTED;
 	}

 #ifndef NO_IO_CACHE