linux-ext4 - [PATCH 14/22] fuse2fs: don't do file data block IO when iomap is enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <175279461286.715479.6258457930261353040.stgit@frogsfrogsfrogs>
Date: Thu, 17 Jul 2025 16:43:02 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: joannelkoong@...il.com, miklos@...redi.hu, John@...ves.net,
 linux-fsdevel@...r.kernel.org, bernd@...ernd.com, linux-ext4@...r.kernel.org,
 neal@...pa.dev
Subject: [PATCH 14/22] 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 45eec59d85faf4..989f9f17cae0a9 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -3059,9 +3059,14 @@ 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 (fuse2fs_iomap_does_fileio(ff))
+		flags |= EXT2_FILE_NOBLOCKIO;
+
+	err = ext2fs_file_open(fs, ino, flags, &file);
 	if (err)
 		return translate_error(fs, ino, err);

@@ -3181,6 +3186,9 @@ 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 (fuse2fs_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) {