Unverified Commit 1505ba06 authored by Bart Van Assche's avatar Bart Van Assche Committed by Christian Brauner
Browse files

fs: Split fcntl_rw_hint() 



Split fcntl_rw_hint() such that there is one helper function per fcntl.
Use READ_ONCE() and WRITE_ONCE() to access the i_write_hint member
instead of protecting such accesses with the inode lock. READ_ONCE() is
not used in I/O path code that reads i_write_hint. Users who want
F_SET_RW_HINT to affect I/O need to make sure that F_SET_RW_HINT has
completed before I/O is submitted that should use the configured write
hint.

Cc: Christoph Hellwig <hch@lst.de>
Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Kanchan Joshi <joshi.k@samsung.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240202203926.2478590-4-bvanassche@acm.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent e769779c

fs/fcntl.c

+24 −21
Original line number Diff line number Diff line
@@ -290,32 +290,33 @@ static bool rw_hint_valid(u64 hint) 
	}

}



static long fcntl_rw_hint(struct file *file, unsigned int cmd,

static long fcntl_get_rw_hint(struct file *file, unsigned int cmd,

			      unsigned long arg)

{

	struct inode *inode = file_inode(file);

	u64 __user *argp = (u64 __user *)arg;

	u64 hint;

	u64 hint = READ_ONCE(inode->i_write_hint);



	switch (cmd) {

	case F_GET_RW_HINT:

		hint = inode->i_write_hint;

	if (copy_to_user(argp, &hint, sizeof(*argp)))

		return -EFAULT;

	return 0;

	case F_SET_RW_HINT:

}



static long fcntl_set_rw_hint(struct file *file, unsigned int cmd,

			      unsigned long arg)

{

	struct inode *inode = file_inode(file);

	u64 __user *argp = (u64 __user *)arg;

	u64 hint;



	if (copy_from_user(&hint, argp, sizeof(hint)))

		return -EFAULT;

	if (!rw_hint_valid(hint))

		return -EINVAL;



		inode_lock(inode);

		inode->i_write_hint = hint;

		inode_unlock(inode);

	WRITE_ONCE(inode->i_write_hint, hint);



	return 0;

	default:

		return -EINVAL;

	}

}



static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
@@ -421,8 +422,10 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, 
		err = memfd_fcntl(filp, cmd, argi);

		break;

	case F_GET_RW_HINT:

		err = fcntl_get_rw_hint(filp, cmd, arg);

		break;

	case F_SET_RW_HINT:

		err = fcntl_rw_hint(filp, cmd, arg);

		err = fcntl_set_rw_hint(filp, cmd, arg);

		break;

	default:

		break;