From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
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 simply compares file_inode(file->f_path.dentry) to
file_inode(file) and if they are equal returns file->f_path.dentry (this is
the common, non-overlayfs case).
In the uncommon case (regular file on overlayfs) it will call into
overlayfs's ->d_native_dentry() to get the underlying dentry matching
file_inode(file).
[*] If possible, it's better simply to use file_inode() instead.
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Tested-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
fs/open.c | 11 +++++++++++
fs/overlayfs/super.c | 16 ++++++++++++++++
include/linux/dcache.h | 1 +
include/linux/fs.h | 2 ++
4 files changed, 30 insertions(+)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1234,6 +1234,8 @@ static inline struct inode *file_inode(c
return f->f_inode;
}
+extern struct dentry *file_dentry(const struct file *file);
+
static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
{
return locks_lock_inode_wait(file_inode(filp), fl);
--- a/fs/open.c
+++ b/fs/open.c
@@ -831,6 +831,17 @@ char *file_path(struct file *filp, char
}
EXPORT_SYMBOL(file_path);
+struct dentry *file_dentry(const struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+
+ if (likely(d_inode(dentry) == file_inode(file)))
+ return dentry;
+ else
+ return dentry->d_op->d_native_dentry(dentry, file_inode(file));
+}
+EXPORT_SYMBOL(file_dentry);
+
/**
* vfs_open - open the file at the given path
* @path: path to open
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -336,14 +336,30 @@ static int ovl_dentry_weak_revalidate(st
return ret;
}
+static struct dentry *ovl_d_native_dentry(struct dentry *dentry,
+ struct inode *inode)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ struct dentry *realentry = ovl_upperdentry_dereference(oe);
+
+ if (realentry && inode == d_inode(realentry))
+ return realentry;
+ realentry = __ovl_dentry_lower(oe);
+ if (realentry && inode == d_inode(realentry))
+ return realentry;
+ BUG();
+}
+
static const struct dentry_operations ovl_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
+ .d_native_dentry = ovl_d_native_dentry,
};
static const struct dentry_operations ovl_reval_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
+ .d_native_dentry = ovl_d_native_dentry,
.d_revalidate = ovl_dentry_revalidate,
.d_weak_revalidate = ovl_dentry_weak_revalidate,
};
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -161,6 +161,7 @@ struct dentry_operations {
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
struct inode *(*d_select_inode)(struct dentry *, unsigned);
+ struct dentry *(*d_native_dentry)(struct dentry *, struct inode *);
} ____cacheline_aligned;
/*
--
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