Unverified Commit fbdc2f6c authored by Christian Brauner's avatar Christian Brauner
Browse files

fs: split out functions to hold writers 

When a mount is marked read-only we set MNT_WRITE_HOLD on it if there
aren't currently any active writers. Split this logic out into simple
helpers that we can use in follow-up patches.

Link: https://lore.kernel.org/r/20210121131959.646623-33-christian.brauner@ubuntu.com


Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
parent e58ace1a

fs/namespace.c

+18 −6
Original line number Diff line number Diff line
@@ -470,10 +470,8 @@ void mnt_drop_write_file(struct file *file) 
}

EXPORT_SYMBOL(mnt_drop_write_file);



static int mnt_make_readonly(struct mount *mnt)

static inline int mnt_hold_writers(struct mount *mnt)

{

	int ret = 0;



	mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;

	/*

	 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
@@ -498,15 +496,29 @@ static int mnt_make_readonly(struct mount *mnt) 
	 * we're counting up here.

	 */

	if (mnt_get_writers(mnt) > 0)

		ret = -EBUSY;

	else

		mnt->mnt.mnt_flags |= MNT_READONLY;

		return -EBUSY;



	return 0;

}



static inline void mnt_unhold_writers(struct mount *mnt)

{

	/*

	 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers

	 * that become unheld will see MNT_READONLY.

	 */

	smp_wmb();

	mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;

}



static int mnt_make_readonly(struct mount *mnt)

{

	int ret;



	ret = mnt_hold_writers(mnt);

	if (!ret)

		mnt->mnt.mnt_flags |= MNT_READONLY;

	mnt_unhold_writers(mnt);

	return ret;

}