Commit 96384574 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

ext4: fail unaligned direct IO write with EINVAL 



Commit bc264fea ("iomap: support incremental iomap_iter advances")
changed the error handling logic in iomap_iter(). Previously any error
from iomap_dio_bio_iter() got propagated to userspace, after this commit
if ->iomap_end returns error, it gets propagated to userspace instead of
an error from iomap_dio_bio_iter(). This results in unaligned writes to
ext4 to silently fallback to buffered IO instead of erroring out.

Now returning ENOTBLK for DIO writes from ext4_iomap_end() seems
unnecessary these days. It is enough to return ENOTBLK from
ext4_iomap_begin() when we don't support DIO write for that particular
file offset (due to hole).

Fixes: bc264fea ("iomap: support incremental iomap_iter advances")
Cc: stable@kernel.org
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Message-ID: <20250901112739.32484-2-jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 46c22a8b

fs/ext4/inode.c

+0 −35
Original line number Diff line number Diff line
@@ -3872,47 +3872,12 @@ static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset, 
	return ret;

}



static inline bool ext4_want_directio_fallback(unsigned flags, ssize_t written)

{

	/* must be a directio to fall back to buffered */

	if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) !=

		    (IOMAP_WRITE | IOMAP_DIRECT))

		return false;



	/* atomic writes are all-or-nothing */

	if (flags & IOMAP_ATOMIC)

		return false;



	/* can only try again if we wrote nothing */

	return written == 0;

}



static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,

			  ssize_t written, unsigned flags, struct iomap *iomap)

{

	/*

	 * Check to see whether an error occurred while writing out the data to

	 * the allocated blocks. If so, return the magic error code for

	 * non-atomic write so that we fallback to buffered I/O and attempt to

	 * complete the remainder of the I/O.

	 * For non-atomic writes, any blocks that may have been

	 * allocated in preparation for the direct I/O will be reused during

	 * buffered I/O. For atomic write, we never fallback to buffered-io.

	 */

	if (ext4_want_directio_fallback(flags, written))

		return -ENOTBLK;



	return 0;

}



const struct iomap_ops ext4_iomap_ops = {

	.iomap_begin		= ext4_iomap_begin,

	.iomap_end		= ext4_iomap_end,

};



const struct iomap_ops ext4_iomap_overwrite_ops = {

	.iomap_begin		= ext4_iomap_overwrite_begin,

	.iomap_end		= ext4_iomap_end,

};



static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,