Commit 213490b3 authored Sep 11, 2012 by Liu Bo Committed by Chris Mason Dec 17, 2012

Btrfs: fix a bug of per-file nocow



Users report a bug, the reproducer is:
$ mkfs.btrfs /dev/loop0
$ mount /dev/loop0 /mnt/btrfs/
$ mkdir /mnt/btrfs/dir
$ chattr +C /mnt/btrfs/dir/
$ dd if=/dev/zero of=/mnt/btrfs/dir/foo bs=4K count=10;
$ lsattr /mnt/btrfs/dir/foo
---------------C- /mnt/btrfs/dir/foo
$ filefrag /mnt/btrfs/dir/foo
/mnt/btrfs/dir/foo: 1 extent found    ---> an extent
$ dd if=/dev/zero of=/mnt/btrfs/dir/foo bs=4K count=1 seek=5 conv=notrunc,nocreat; sync
$ filefrag /mnt/btrfs/dir/foo
/mnt/btrfs/dir/foo: 3 extents found   ---> with nocow, btrfs breaks the extent into three parts

The new created file should not only inherit the NODATACOW flag, but also
honor NODATASUM flag, because we must do COW on a file extent with checksum.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

parent 9c52057c

fs/btrfs/inode.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -4818,8 +4818,7 @@ static struct inode btrfs_new_inode(struct btrfs_trans_handle trans,
		if (S_ISREG(mode)) {
		if (btrfs_test_opt(root, NODATASUM))
		BTRFS_I(inode)->flags \|= BTRFS_INODE_NODATASUM;
		if (btrfs_test_opt(root, NODATACOW) \|\|
		(BTRFS_I(dir)->flags & BTRFS_INODE_NODATACOW))
		if (btrfs_test_opt(root, NODATACOW))
		BTRFS_I(inode)->flags \|= BTRFS_INODE_NODATACOW;
		}

fs/btrfs/ioctl.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -141,8 +141,11 @@ void btrfs_inherit_iflags(struct inode inode, struct inode dir)
		BTRFS_I(inode)->flags \|= BTRFS_INODE_COMPRESS;
		}

		if (flags & BTRFS_INODE_NODATACOW)
		if (flags & BTRFS_INODE_NODATACOW) {
		BTRFS_I(inode)->flags \|= BTRFS_INODE_NODATACOW;
		if (S_ISREG(inode->i_mode))
		BTRFS_I(inode)->flags \|= BTRFS_INODE_NODATASUM;
		}

		btrfs_update_iflags(inode);
		}