linux-ext4 - [PATCH 13/16] fuse2fs: don't do file data block IO when iomap is enabled

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Message-ID: <174787198668.1484996.15426837869307835566.stgit@frogsfrogsfrogs>
Date: Wed, 21 May 2025 17:14:14 -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 13/16] fuse2fs: don't do file data block IO when iomap is
 enabled

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

When iomap is in use for the page cache, the kernel will take care of
all the file data block IO for us, including zeroing of punched ranges
and post-EOF bytes.  fuse2fs only needs to do IO for inline data.

Therefore, set the NOBLOCKIO ext2_file flag so that libext2fs will not
do any regular file IO to or from disk blocks at all.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 misc/fuse2fs.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index aeb2b6fbc28401..842ea3a191fa44 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -2863,9 +2863,14 @@ static int truncate_helper(struct fuse2fs *ff, ext2_ino_t ino, off_t new_size)
 	ext2_file_t file;
 	__u64 old_isize;
 	errcode_t err;
+	int flags = EXT2_FILE_WRITE;
 	int ret = 0;

-	err = ext2fs_file_open(fs, ino, EXT2_FILE_WRITE, &file);
+	/* the kernel handles all eof zeroing for us in iomap mode */
+	if (iomap_does_fileio(ff))
+		flags |= EXT2_FILE_NOBLOCKIO;
+
+	err = ext2fs_file_open(fs, ino, flags, &file);
 	if (err)
 		return translate_error(fs, ino, err);

@@ -2987,6 +2992,9 @@ static int __op_open(struct fuse2fs *ff, const char *path,
 		file->open_flags |= EXT2_FILE_WRITE;
 		break;
 	}
+	/* the kernel handles all block IO for us in iomap mode */
+	if (iomap_does_fileio(ff))
+		file->open_flags |= EXT2_FILE_NOBLOCKIO;
 	if (fp->flags & O_APPEND) {
 		/* the kernel doesn't allow truncation of an append-only file */
 		if (fp->flags & O_TRUNC) {