Commit a2ad63da authored by NeilBrown's avatar NeilBrown Committed by Andrew Morton
Browse files

VFS: add FMODE_CAN_ODIRECT file flag 

Currently various places test if direct IO is possible on a file by
checking for the existence of the direct_IO address space operation.
This is a poor choice, as the direct_IO operation may not be used - it is
only used if the generic_file_*_iter functions are called for direct IO
and some filesystems - particularly NFS - don't do this.

Instead, introduce a new f_mode flag: FMODE_CAN_ODIRECT and change the
various places to check this (avoiding pointer dereferences).
do_dentry_open() will set this flag if ->direct_IO is present, so
filesystems do not need to be changed.

NFS *is* changed, to set the flag explicitly and discard the direct_IO
entry in the address_space_operations for files.

Other filesystems which currently use noop_direct_IO could usefully be
changed to set this flag instead.

Link: https://lkml.kernel.org/r/164859778128.29473.15189737957277399416.stgit@noble.brown


Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Tested-by: default avatarDavid Howells <dhowells@redhat.com>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 6341a446

drivers/block/loop.c

+2 −2
Original line number Diff line number Diff line
@@ -187,7 +187,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio) 
	if (dio) {

		if (queue_logical_block_size(lo->lo_queue) >= sb_bsize &&

		    !(lo->lo_offset & dio_align) &&

				mapping->a_ops->direct_IO)

		    (file->f_mode & FMODE_CAN_ODIRECT))

			use_dio = true;

		else

			use_dio = false;

fs/fcntl.c

+4 −5
Original line number Diff line number Diff line
@@ -56,11 +56,10 @@ static int setfl(int fd, struct file * filp, unsigned long arg) 
		   arg |= O_NONBLOCK;



	/* Pipe packetized mode is controlled by O_DIRECT flag */

	if (!S_ISFIFO(inode->i_mode) && (arg & O_DIRECT)) {

		if (!filp->f_mapping || !filp->f_mapping->a_ops ||

			!filp->f_mapping->a_ops->direct_IO)

	if (!S_ISFIFO(inode->i_mode) &&

	    (arg & O_DIRECT) &&

	    !(filp->f_mode & FMODE_CAN_ODIRECT))

		return -EINVAL;

	}



	if (filp->f_op->check_flags)

		error = filp->f_op->check_flags(arg);

fs/nfs/file.c

+2 −1
Original line number Diff line number Diff line
@@ -69,6 +69,8 @@ nfs_file_open(struct inode *inode, struct file *filp) 
		return res;



	res = nfs_open(inode, filp);

	if (res == 0)

		filp->f_mode |= FMODE_CAN_ODIRECT;

	return res;

}
@@ -536,7 +538,6 @@ const struct address_space_operations nfs_file_aops = { 
	.write_end = nfs_write_end,

	.invalidate_folio = nfs_invalidate_folio,

	.releasepage = nfs_release_page,

	.direct_IO = nfs_direct_IO,

#ifdef CONFIG_MIGRATION

	.migratepage = nfs_migrate_page,

#endif

fs/open.c

+4 −5
Original line number Diff line number Diff line
@@ -834,16 +834,15 @@ static int do_dentry_open(struct file *f, 
	if ((f->f_mode & FMODE_WRITE) &&

	     likely(f->f_op->write || f->f_op->write_iter))

		f->f_mode |= FMODE_CAN_WRITE;

	if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO)

		f->f_mode |= FMODE_CAN_ODIRECT;



	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);



	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);



	/* NB: we're sure to have correct a_ops only after f_op->open */

	if (f->f_flags & O_DIRECT) {

		if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)

	if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT))

		return -EINVAL;

	}



	/*

	 * XXX: Huge page cache doesn't support writing yet. Drop all page

fs/overlayfs/file.c

+4 −9
Original line number Diff line number Diff line
@@ -82,11 +82,8 @@ static int ovl_change_flags(struct file *file, unsigned int flags) 
	if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))

		return -EPERM;



	if (flags & O_DIRECT) {

		if (!file->f_mapping->a_ops ||

		    !file->f_mapping->a_ops->direct_IO)

	if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))

		return -EINVAL;

	}



	if (file->f_op->check_flags) {

		err = file->f_op->check_flags(flags);
@@ -306,8 +303,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) 


	ret = -EINVAL;

	if (iocb->ki_flags & IOCB_DIRECT &&

	    (!real.file->f_mapping->a_ops ||

	     !real.file->f_mapping->a_ops->direct_IO))

	    !(real.file->f_mode & FMODE_CAN_ODIRECT))

		goto out_fdput;



	old_cred = ovl_override_creds(file_inode(file)->i_sb);
@@ -367,8 +363,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) 


	ret = -EINVAL;

	if (iocb->ki_flags & IOCB_DIRECT &&

	    (!real.file->f_mapping->a_ops ||

	     !real.file->f_mapping->a_ops->direct_IO))

	    !(real.file->f_mode & FMODE_CAN_ODIRECT))

		goto out_fdput;



	if (!ovl_should_sync(OVL_FS(inode->i_sb)))