Commit 3cc79392 authored Jun 25, 2014 by Filipe Manana Committed by Chris Mason Jul 03, 2014

Btrfs: atomically set inode->i_flags in btrfs_update_iflags



This change is based on the corresponding recent change for ext4:

  ext4: atomically set inode->i_flags in ext4_set_inode_flags()

That has the following commit message that applies to btrfs as well:

  "Use cmpxchg() to atomically set i_flags instead of clearing out the
   S_IMMUTABLE, S_APPEND, etc. flags and then setting them from the
   EXT4_IMMUTABLE_FL, EXT4_APPEND_FL flags, since this opens up a race
   where an immutable file has the immutable flag cleared for a brief
   window of time."

Replacing EXT4_IMMUTABLE_FL and EXT4_APPEND_FL with BTRFS_INODE_IMMUTABLE
and BTRFS_INODE_APPEND, respectively.

Reviewed-by: David Sterba <dsterba@suse.cz>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 472b909f

fs/btrfs/ioctl.c

+10 −7

Original line number	Diff line number	Diff line
		@@ -136,19 +136,22 @@ static unsigned int btrfs_flags_to_ioctl(unsigned int flags)
		void btrfs_update_iflags(struct inode *inode)
		{
		struct btrfs_inode *ip = BTRFS_I(inode);

		inode->i_flags &= ~(S_SYNC\|S_APPEND\|S_IMMUTABLE\|S_NOATIME\|S_DIRSYNC);
		unsigned int new_fl = 0;

		if (ip->flags & BTRFS_INODE_SYNC)
		inode->i_flags \|= S_SYNC;
		new_fl \|= S_SYNC;
		if (ip->flags & BTRFS_INODE_IMMUTABLE)
		inode->i_flags \|= S_IMMUTABLE;
		new_fl \|= S_IMMUTABLE;
		if (ip->flags & BTRFS_INODE_APPEND)
		inode->i_flags \|= S_APPEND;
		new_fl \|= S_APPEND;
		if (ip->flags & BTRFS_INODE_NOATIME)
		inode->i_flags \|= S_NOATIME;
		new_fl \|= S_NOATIME;
		if (ip->flags & BTRFS_INODE_DIRSYNC)
		inode->i_flags \|= S_DIRSYNC;
		new_fl \|= S_DIRSYNC;

		set_mask_bits(&inode->i_flags,
		S_SYNC \| S_APPEND \| S_IMMUTABLE \| S_NOATIME \| S_DIRSYNC,
		new_fl);
		}

		/*