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authorDave Chinner <dchinner@redhat.com>2016-01-04 16:28:25 +1100
committerDave Chinner <david@fromorbit.com>2016-01-04 16:28:25 +1100
commita6d7636e8d0fd94fd1937db91d5b06a91fa85dde (patch)
tree41b326d5e1ee03a7948c692064002d18282d3fe2
parent3b0fe47805802216087259b07de691ef47ff6fbc (diff)
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xfs: fix recursive splice read locking with DAX
Doing a splice read (generic/249) generates a lockdep splat because we recursively lock the inode iolock in this path: SyS_sendfile64 do_sendfile do_splice_direct splice_direct_to_actor do_splice_to xfs_file_splice_read <<<<<< lock here default_file_splice_read vfs_readv do_readv_writev do_iter_readv_writev xfs_file_read_iter <<<<<< then here The issue here is that for DAX inodes we need to avoid the page cache path and hence simply push it into the normal read path. Unfortunately, we can't tell down at xfs_file_read_iter() whether we are being called from the splice path and hence we cannot avoid the locking at this layer. Hence we simply have to drop the inode locking at the higher splice layer for DAX. Signed-off-by: Dave Chinner <dchinner@redhat.com> Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
-rw-r--r--fs/xfs/xfs_file.c25
1 files changed, 16 insertions, 9 deletions
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index f5392ab2def1..ebe9b8290a70 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -402,19 +402,26 @@ xfs_file_splice_read(
if (XFS_FORCED_SHUTDOWN(ip->i_mount))
return -EIO;
- xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-
trace_xfs_file_splice_read(ip, count, *ppos, ioflags);
- /* for dax, we need to avoid the page cache */
- if (IS_DAX(VFS_I(ip)))
- ret = default_file_splice_read(infilp, ppos, pipe, count, flags);
- else
- ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
- if (ret > 0)
- XFS_STATS_ADD(ip->i_mount, xs_read_bytes, ret);
+ /*
+ * DAX inodes cannot ues the page cache for splice, so we have to push
+ * them through the VFS IO path. This means it goes through
+ * ->read_iter, which for us takes the XFS_IOLOCK_SHARED. Hence we
+ * cannot lock the splice operation at this level for DAX inodes.
+ */
+ if (IS_DAX(VFS_I(ip))) {
+ ret = default_file_splice_read(infilp, ppos, pipe, count,
+ flags);
+ goto out;
+ }
+ xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+ ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+out:
+ if (ret > 0)
+ XFS_STATS_ADD(ip->i_mount, xs_read_bytes, ret);
return ret;
}