On Thu, Mar 03, 2016 at 09:16:33AM +0100, Miklos Szeredi wrote:
My plan was to introduce a file_dentry() helper that MUST be used by
filesystems to get the dentry from the file and that makes sure it's
the right one (check against file_inode()). If not, then we could
call into overlayfs to return the right one, similar to
->d_select_inode(), except we want to have a dentry and we want to
have *a particular dentry* matching file_inode() (the file could have
been copied up in the mean time).
Something like the following (untested, against overlayfs-next.git)
Thanks,
Miklos
---
fs/nfs/dir.c | 6 +++---
fs/nfs/inode.c | 2 +-
fs/nfs/nfs4file.c | 4 ++--
fs/open.c | 11 +++++++++++
fs/overlayfs/super.c | 16 ++++++++++++++++
include/linux/dcache.h | 1 +
include/linux/fs.h | 2 ++
7 files changed, 36 insertions(+), 6 deletions(-)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -377,7 +377,7 @@ int nfs_readdir_xdr_filler(struct page *
again:
timestamp = jiffies;
gencount = nfs_inc_attr_generation_counter();
- error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
+ error = NFS_PROTO(inode)->readdir(file_dentry(file), cred, entry->cookie, pages,
NFS_SERVER(inode)->dtsize, desc->plus);
if (error < 0) {
/* We requested READDIRPLUS, but the server doesn't grok it */
@@ -560,7 +560,7 @@ int nfs_readdir_page_filler(nfs_readdir_
count++;
if (desc->plus != 0)
- nfs_prime_dcache(desc->file->f_path.dentry, entry);
+ nfs_prime_dcache(file_dentry(desc->file), entry);
status = nfs_readdir_add_to_array(entry, page);
if (status != 0)
@@ -864,7 +864,7 @@ static bool nfs_dir_mapping_need_revalid
*/
static int nfs_readdir(struct file *file, struct dir_context *ctx)
{
- struct dentry *dentry = file->f_path.dentry;
+ struct dentry *dentry = file_dentry(file);
struct inode *inode = d_inode(dentry);
nfs_readdir_descriptor_t my_desc,
*desc = &my_desc;
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -940,7 +940,7 @@ int nfs_open(struct inode *inode, struct
{
struct nfs_open_context *ctx;
- ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
+ ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
if (IS_ERR(ctx))
return PTR_ERR(ctx);
nfs_file_set_open_context(filp, ctx);
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -26,7 +26,7 @@ static int
nfs4_file_open(struct inode *inode, struct file *filp)
{
struct nfs_open_context *ctx;
- struct dentry *dentry = filp->f_path.dentry;
+ struct dentry *dentry = file_dentry(filp);
struct dentry *parent = NULL;
struct inode *dir;
unsigned openflags = filp->f_flags;
@@ -57,7 +57,7 @@ nfs4_file_open(struct inode *inode, stru
parent = dget_parent(dentry);
dir = d_inode(parent);
- ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
+ ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
err = PTR_ERR(ctx);
if (IS_ERR(ctx))
goto out;
--- 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 (d_inode(dentry) == file_inode(file))
+ return dentry;
+ else
+ return dentry->d_op->d_select_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_select_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_select_dentry = ovl_d_select_dentry,
};
static const struct dentry_operations ovl_reval_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
+ .d_select_dentry = ovl_d_select_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_select_dentry)(struct dentry *, struct inode *);
} ____cacheline_aligned;
/*
