fs: add file_dentry()
This series fixes bugs in nfs and ext4 due to 4bacc9c9234c ("overlayfs:
Make f_path always point to the overlay and f_inode to the underlay").
Regular files opened on overlayfs will result in the file being opened on
the underlying filesystem, while f_path points to the overlayfs
mount/dentry.
This confuses filesystems which get the dentry from struct file and assume
it's theirs.
Add a new helper, file_dentry() [*], to get the filesystem's own dentry
from the file. This checks file->f_path.dentry->d_flags against
DCACHE_OP_REAL, and returns file->f_path.dentry if DCACHE_OP_REAL is not
set (this is the common, non-overlayfs case).
In the uncommon case it will call into overlayfs's ->d_real() to get the
underlying dentry, matching file_inode(file).
The reason we need to check against the inode is that if the file is copied
up while being open, d_real() would return the upper dentry, while the open
file comes from the lower dentry.
[*] If possible, it's better simply to use file_inode() instead.
Signed-off-by: Miklos Szeredi <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>
Tested-by: Goldwyn Rodrigues <[email protected]>
Reviewed-by: Trond Myklebust <[email protected]>
Cc: <[email protected]> # v4.2
Cc: David Howells <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Daniel Axtens <[email protected]>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ef64984..5d972e6 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -295,6 +295,37 @@
}
}
+static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)
+{
+ struct dentry *real;
+
+ if (d_is_dir(dentry)) {
+ if (!inode || inode == d_inode(dentry))
+ return dentry;
+ goto bug;
+ }
+
+ real = ovl_dentry_upper(dentry);
+ if (real && (!inode || inode == d_inode(real)))
+ return real;
+
+ real = ovl_dentry_lower(dentry);
+ if (!real)
+ goto bug;
+
+ if (!inode || inode == d_inode(real))
+ return real;
+
+ /* Handle recursion */
+ if (real->d_flags & DCACHE_OP_REAL)
+ return real->d_op->d_real(real, inode);
+
+bug:
+ WARN(1, "ovl_d_real(%pd4, %s:%lu\n): real dentry not found\n", dentry,
+ inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
+ return dentry;
+}
+
static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -339,11 +370,13 @@
static const struct dentry_operations ovl_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
+ .d_real = ovl_d_real,
};
static const struct dentry_operations ovl_reval_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
+ .d_real = ovl_d_real,
.d_revalidate = ovl_dentry_revalidate,
.d_weak_revalidate = ovl_dentry_weak_revalidate,
};
