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authorMiklos Szeredi <miklos@szeredi.hu>2016-03-26 16:14:37 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-03-26 16:14:37 -0400
commitd101a125954eae1d397adda94ca6319485a50493 (patch)
tree0f5853af51446f389c60f1a25f3875ef8a75ba41 /fs/overlayfs
parentc9af28fdd44922a6c10c9f8315718408af98e315 (diff)
downloadop-kernel-dev-d101a125954eae1d397adda94ca6319485a50493.zip
op-kernel-dev-d101a125954eae1d397adda94ca6319485a50493.tar.gz
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 <mszeredi@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Tested-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Cc: <stable@vger.kernel.org> # v4.2 Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Daniel Axtens <dja@axtens.net>
Diffstat (limited to 'fs/overlayfs')
-rw-r--r--fs/overlayfs/super.c33
1 files changed, 33 insertions, 0 deletions
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 void ovl_dentry_release(struct dentry *dentry)
}
}
+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 int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
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,
};
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