Looks fine, although the fs.h addition would usually warrant a Cc to
Al and fsdevel. (thus included as a full quote)
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
On Fri, Jan 26, 2018 at 05:10:28PM -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 | 25 +++++++++++++++----------
> include/linux/fs.h | 5 +++++
> 2 files changed, 20 insertions(+), 10 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index bcc58c2..85a119e 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 < dest) {
> - inode_lock(src);
> + inode_lock_shared(src);
> inode_lock_nested(dest, I_MUTEX_NONDIR2);
> } else {
> /* src >= dest */
> @@ -1271,7 +1274,7 @@ xfs_iolock_two_inodes_and_break_layout(
> if (error == -EWOULDBLOCK) {
> inode_unlock(dest);
> if (src < dest)
> - inode_unlock(src);
> + inode_unlock_shared(src);
> error = break_layout(dest, true);
> if (error)
> return error;
> @@ -1280,11 +1283,11 @@ xfs_iolock_two_inodes_and_break_layout(
> if (error) {
> inode_unlock(dest);
> if (src < dest)
> - inode_unlock(src);
> + inode_unlock_shared(src);
> return error;
> }
> if (src > dest)
> - inode_lock_nested(src, I_MUTEX_NONDIR2);
> + inode_lock_shared_nested(src, I_MUTEX_NONDIR2);
> return 0;
> }
>
> @@ -1324,7 +1327,7 @@ xfs_reflink_remap_range(
> if (same_inode)
> xfs_ilock(src, XFS_MMAPLOCK_EXCL);
> else
> - xfs_lock_two_inodes(src, XFS_MMAPLOCK_EXCL, dest,
> + xfs_lock_two_inodes(src, XFS_MMAPLOCK_SHARED, dest,
> XFS_MMAPLOCK_EXCL);
>
> /* Check file eligibility and prepare for block sharing. */
> @@ -1393,10 +1396,12 @@ 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;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7f8d96d..5cbeab8 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -748,6 +748,11 @@ static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
> down_write_nested(&inode->i_rwsem, subclass);
> }
>
> +static inline void inode_lock_shared_nested(struct inode *inode, unsigned subclass)
> +{
> + down_read_nested(&inode->i_rwsem, subclass);
> +}
> +
> void lock_two_nondirectories(struct inode *, struct inode*);
> void unlock_two_nondirectories(struct inode *, struct inode*);
>
>
> --
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