If two overlayfs filesystems are stacked on top of each other, then we need
to recurse when opening a file. This used to work and was first broken by:
4bacc9c9234c ("overlayfs: Make f_path always point to the overlay...")
and fixed by:
1c8a47df36d7 ("ovl: fix open in stacked overlay")
But it looks like it was re-introduced in:
2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()")
I know close to nothing about VFS/overlayfs so this might be completely
wrong for many reasons but it fixes the following test case for me:
#!/bin/bash -xeu
tmpdir=$(mktemp -d)
pushd ${tmpdir}
mkdir -p {upper,lower,work}
echo -n 'rocks' > lower/ksplice
mount -t overlay level_zero upper -o
lowerdir=lower,upperdir=upper,workdir=work
cat upper/ksplice
tmpdir2=$(mktemp -d)
pushd ${tmpdir2}
mkdir -p {upper,work}
mount -t overlay level_one upper -o
lowerdir=${tmpdir}/upper,upperdir=upper,workdir=work
ls -l upper/ksplice
cat upper/ksplice
For sanity checking, I've run the test-suite mentionned in
Documentation/filesystems/overlayfs.txt:
git://git.infradead.org/users/dhowells/unionmount-testsuite.git
Though with and without this patch it returned zero so I am assuming it
does not contain any tests with stacked overlayfs.
Fixes: 2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()")
Cc: Al Viro <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Signed-off-by: Quentin Casasnovas <[email protected]>
---
fs/overlayfs/super.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index edd46a0e951d..ae0b36474a9a 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -321,16 +321,22 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
}
real = ovl_dentry_upper(dentry);
- if (real && (!inode || inode == d_inode(real)))
- return real;
+ if (real && inode && inode == d_inode(real))
+ return real;
+
+ if (real && !inode && d_inode(real))
+ return d_real(real, d_inode(real), open_flags);
real = ovl_dentry_lower(dentry);
if (!real)
goto bug;
- if (!inode || inode == d_inode(real))
+ if (inode && inode == d_inode(real))
return real;
+ if (!inode && d_inode(real))
+ return d_real(real, d_inode(real), open_flags);
+
/* Handle recursion */
return d_real(real, inode, open_flags);
bug:
--
2.11.0.rc2
