Overlay file f_pos is the master copy that is preserved
through copy up, but only real fs knows how to SEEK_HOLE/
SEEK_DATA. So we copy f_pos from overlay file, perform the seek
on real file and copy f_pos back to overlay file.
Fixes: d1d04ef8572b ("ovl: stack file ops")
Reported-by: Eddie Horng <eddiehorng.tw@xxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
Miklos,
I verified no regressions with xfstests quick tests.
The improved generic/seek tests that I posted to fstests
are failing on master and passing with this fix.
Thanks,
Amir.
fs/overlayfs/file.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 84dd957efa24..0d472940ce9e 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -145,11 +145,30 @@ static int ovl_release(struct inode *inode, struct file *file)
static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
{
- struct inode *realinode = ovl_inode_real(file_inode(file));
+ struct fd real;
+ const struct cred *old_cred;
+ ssize_t ret;
- return generic_file_llseek_size(file, offset, whence,
- realinode->i_sb->s_maxbytes,
- i_size_read(realinode));
+ ret = ovl_real_fdget(file, &real);
+ if (ret)
+ return ret;
+
+ /*
+ * Overlay file f_pos is the master copy that is preserved
+ * through copy up, but only real fs knows how to SEEK_HOLE/
+ * SEEK_DATA.
+ */
+ real.file->f_pos = file->f_pos;
+
+ old_cred = ovl_override_creds(file_inode(file)->i_sb);
+ ret = vfs_llseek(real.file, offset, whence);
+ revert_creds(old_cred);
+
+ file->f_pos = real.file->f_pos;
+
+ fdput(real);
+
+ return ret;
}
static void ovl_file_accessed(struct file *file)
--
2.17.1
