On Sat, Jan 20, 2018 at 09:34:03PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Reflink and dedupe operations remap blocks from a source file into a
> destination file. The destination file needs exclusive locks on all
> levels because we're updating its block map, but the source file isn't
> undergoing any block map changes so we can use a shared lock.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_reflink.c | 50 +++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 37 insertions(+), 13 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index ce523dd..5d1ff5a 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1202,13 +1202,16 @@ xfs_reflink_remap_blocks(
>
> /* drange = (destoff, destoff + len); srange = (srcoff, srcoff + len) */
> while (len) {
> + uint lock_mode;
> +
> trace_xfs_reflink_remap_blocks_loop(src, srcoff, len,
> dest, destoff);
> +
> /* Read extent from the source file */
> nimaps = 1;
> - xfs_ilock(src, XFS_ILOCK_EXCL);
> + lock_mode = xfs_ilock_data_map_shared(src);
> error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
> - xfs_iunlock(src, XFS_ILOCK_EXCL);
> + xfs_iunlock(src, lock_mode);
> if (error)
> goto err;
> ASSERT(nimaps == 1);
> @@ -1260,7 +1263,7 @@ xfs_iolock_two_inodes_and_break_layout(
>
> retry:
> if (src_first) {
> - inode_lock(src);
> + inode_lock_shared(src);
Hm, I guess this could make my comment on the previous patch more
difficult. Oh well.
> inode_lock_nested(dest, I_MUTEX_NONDIR2);
> } else {
> inode_lock(dest);
> @@ -1270,7 +1273,7 @@ xfs_iolock_two_inodes_and_break_layout(
> if (error == -EWOULDBLOCK) {
> inode_unlock(dest);
> if (src_first)
> - inode_unlock(src);
> + inode_unlock_shared(src);
> error = break_layout(dest, true);
> if (error)
> return error;
> @@ -1278,14 +1281,36 @@ xfs_iolock_two_inodes_and_break_layout(
> } else if (error) {
> inode_unlock(dest);
> if (src_first)
> - inode_unlock(src);
> + inode_unlock_shared(src);
> return error;
> }
> if (src_last)
> - inode_lock_nested(src, I_MUTEX_NONDIR2);
> + down_read_nested(&src->i_rwsem, I_MUTEX_NONDIR2);
> return 0;
> }
>
> +static void
> +xfs_reflink_mmaplock_two(
> + struct xfs_inode *src,
> + struct xfs_inode *dest)
> +{
> + int i = 0;
> +
> + if (src->i_ino == dest->i_ino) {
> + xfs_ilock(src, XFS_MMAPLOCK_EXCL);
> + return;
> + }
> +
> + if (src->i_ino < dest->i_ino) {
> + xfs_ilock(src, XFS_MMAPLOCK_SHARED);
> + i++;
> + }
> + xfs_ilock(dest, XFS_MMAPLOCK_EXCL + (i << XFS_MMAPLOCK_SHIFT));
> + i++;
> + if (src->i_ino > dest->i_ino)
> + xfs_ilock(src, XFS_MMAPLOCK_SHARED + (i << XFS_MMAPLOCK_SHIFT));
> +}
> +
I am kind of wondering if this one could be replaced with a refactor of
xfs_lock_two_inodes() to take two sets of lock flags (then create a
wrapper to preserve the current signature that just passes the same set
of flags for both inodes).
Brian
> /*
> * Link a range of blocks from one file to another.
> */
> @@ -1319,10 +1344,7 @@ xfs_reflink_remap_range(
> ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
> if (ret)
> return ret;
> - if (same_inode)
> - xfs_ilock(src, XFS_MMAPLOCK_EXCL);
> - else
> - xfs_lock_two_inodes(src, dest, XFS_MMAPLOCK_EXCL);
> + xfs_reflink_mmaplock_two(src, dest);
>
> /* Check file eligibility and prepare for block sharing. */
> ret = -EINVAL;
> @@ -1385,10 +1407,12 @@ xfs_reflink_remap_range(
> is_dedupe);
>
> out_unlock:
> - xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
> + xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
> + if (!same_inode)
> + xfs_iunlock(src, XFS_MMAPLOCK_SHARED);
> + inode_unlock(inode_out);
> if (!same_inode)
> - xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
> - unlock_two_nondirectories(inode_in, inode_out);
> + inode_unlock_shared(inode_in);
> if (ret)
> trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
> return ret;
>
> --
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