ovl: Fix ovl_getattr() to get number of blocks from lower

If an inode has been copied up metadata only, then we need to query the
number of blocks from lower and fill up the stat->st_blocks.

We need to be careful about races where we are doing stat on one cpu and
data copy up is taking place on other cpu.  We want to return
stat->st_blocks either from lower or stable upper and not something in
between.  Hence, ovl_has_upperdata() is called first to figure out whether
block reporting will take place from lower or upper.

We now support metacopy dentries in middle layer.  That means number of
blocks reporting needs to come from lowest data dentry and this could be
different from lower dentry.  Hence we end up making a separate
vfs_getxattr() call for metacopy dentries to get number of blocks.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 34 insertions, 1 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index d3e65d2a1b83..2a5a38c81961 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -145,6 +145,9 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
 	bool samefs = ovl_same_sb(dentry->d_sb);
 	struct ovl_layer *lower_layer = NULL;
 	int err;
+	bool metacopy_blocks = false;
+
+	metacopy_blocks = ovl_is_metacopy_dentry(dentry);
 
 	type = ovl_path_real(dentry, &realpath);
 	old_cred = ovl_override_creds(dentry->d_sb);
@@ -166,7 +169,8 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
 			lower_layer = ovl_layer_lower(dentry);
 		} else if (OVL_TYPE_ORIGIN(type)) {
 			struct kstat lowerstat;
-			u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
+			u32 lowermask = STATX_INO | STATX_BLOCKS |
+					(!is_dir ? STATX_NLINK : 0);
 
 			ovl_path_lower(dentry, &realpath);
 			err = vfs_getattr(&realpath, &lowerstat,
@@ -195,6 +199,35 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
 				stat->ino = lowerstat.ino;
 				lower_layer = ovl_layer_lower(dentry);
 			}
+
+			/*
+			 * If we are querying a metacopy dentry and lower
+			 * dentry is data dentry, then use the blocks we
+			 * queried just now. We don't have to do additional
+			 * vfs_getattr(). If lower itself is metacopy, then
+			 * additional vfs_getattr() is unavoidable.
+			 */
+			if (metacopy_blocks &&
+			    realpath.dentry == ovl_dentry_lowerdata(dentry)) {
+				stat->blocks = lowerstat.blocks;
+				metacopy_blocks = false;
+			}
+		}
+
+		if (metacopy_blocks) {
+			/*
+			 * If lower is not same as lowerdata or if there was
+			 * no origin on upper, we can end up here.
+			 */
+			struct kstat lowerdatastat;
+			u32 lowermask = STATX_BLOCKS;
+
+			ovl_path_lowerdata(dentry, &realpath);
+			err = vfs_getattr(&realpath, &lowerdatastat,
+					  lowermask, flags);
+			if (err)
+				goto out;
+			stat->blocks = lowerdatastat.blocks;
 		}
 	}