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Date: Fri, 15 Sep 2017 09:32:26 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>
Subject: Re: [GIT PULL] overlayfs update for 4.14
On Thu, Sep 14, 2017 at 01:24:22PM -0700, Linus Torvalds wrote:
> I just don't see any reason why those two "flags" arguments are separate.
Fine. Here's a patch reverting the new flags and adding O_UPPER.
Thanks,
Miklos
---
From: Miklos Szeredi <mszeredi@...hat.com>
Subject: vfs: d_real: merge flags and open_flags
Remove the second "flags" argument of d_real(). The remaining flags are
now used by:
- open() to pass the open flags, which lets us decide whether the file
needs to be copied up or not
- by the VFS when it needs to check if dentry in question is writable
(i.e. pass O_UPPER, which returns upper dentry or NULL)
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
Documentation/filesystems/Locking | 2 +-
Documentation/filesystems/vfs.txt | 2 +-
fs/inode.c | 2 +-
fs/namespace.c | 2 +-
fs/open.c | 4 ++--
fs/overlayfs/super.c | 12 ++++++------
include/linux/dcache.h | 17 ++++++++---------
include/linux/fcntl.h | 11 +++++++++++
include/linux/fs.h | 2 +-
9 files changed, 32 insertions(+), 22 deletions(-)
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -22,7 +22,7 @@ be able to use diff(1).
struct vfsmount *(*d_automount)(struct path *path);
int (*d_manage)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
- unsigned int, unsigned int);
+ unsigned int);
locking rules:
rename_lock ->d_lock may block rcu-walk
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -988,7 +988,7 @@ struct dentry_operations {
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
- unsigned int, unsigned int);
+ unsigned int);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1578,7 +1578,7 @@ static void update_ovl_inode_times(struc
if (rcu || likely(!(dentry->d_flags & DCACHE_OP_REAL)))
return;
- upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
+ upperdentry = d_real(dentry, NULL, O_UPPER);
/*
* If file is on lower then we can't update atime, so no worries about
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -467,7 +467,7 @@ static inline int may_write_real(struct
return 0;
/* File refers to upper, writable layer? */
- upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
+ upperdentry = d_real(dentry, NULL, O_UPPER);
if (upperdentry && file_inode(file) == d_inode(upperdentry))
return 0;
--- a/fs/open.c
+++ b/fs/open.c
@@ -96,7 +96,7 @@ long vfs_truncate(const struct path *pat
* write access on the upper inode, not on the overlay inode. For
* non-overlay filesystems d_real() is an identity function.
*/
- upperdentry = d_real(path->dentry, NULL, O_WRONLY, 0);
+ upperdentry = d_real(path->dentry, NULL, O_WRONLY);
error = PTR_ERR(upperdentry);
if (IS_ERR(upperdentry))
goto mnt_drop_write_and_out;
@@ -857,7 +857,7 @@ EXPORT_SYMBOL(file_path);
int vfs_open(const struct path *path, struct file *file,
const struct cred *cred)
{
- struct dentry *dentry = d_real(path->dentry, NULL, file->f_flags, 0);
+ struct dentry *dentry = d_real(path->dentry, NULL, file->f_flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -70,12 +70,12 @@ static int ovl_check_append_only(struct
static struct dentry *ovl_d_real(struct dentry *dentry,
const struct inode *inode,
- unsigned int open_flags, unsigned int flags)
+ unsigned int flags)
{
struct dentry *real;
int err;
- if (flags & D_REAL_UPPER)
+ if (flags & O_UPPER)
return ovl_dentry_upper(dentry);
if (!d_is_reg(dentry)) {
@@ -84,8 +84,8 @@ static struct dentry *ovl_d_real(struct
goto bug;
}
- if (open_flags) {
- err = ovl_open_maybe_copy_up(dentry, open_flags);
+ if (flags) {
+ err = ovl_open_maybe_copy_up(dentry, flags);
if (err)
return ERR_PTR(err);
}
@@ -93,7 +93,7 @@ static struct dentry *ovl_d_real(struct
real = ovl_dentry_upper(dentry);
if (real && (!inode || inode == d_inode(real))) {
if (!inode) {
- err = ovl_check_append_only(d_inode(real), open_flags);
+ err = ovl_check_append_only(d_inode(real), flags);
if (err)
return ERR_PTR(err);
}
@@ -105,7 +105,7 @@ static struct dentry *ovl_d_real(struct
goto bug;
/* Handle recursion */
- real = d_real(real, inode, open_flags, 0);
+ real = d_real(real, inode, flags);
if (!inode || inode == d_inode(real))
return real;
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -147,7 +147,7 @@ struct dentry_operations {
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
- unsigned int, unsigned int);
+ unsigned int);
} ____cacheline_aligned;
/*
@@ -562,27 +562,26 @@ static inline struct dentry *d_backing_d
return upper;
}
-/* d_real() flags */
-#define D_REAL_UPPER 0x2 /* return upper dentry or NULL if non-upper */
-
/**
* d_real - Return the real dentry
* @dentry: the dentry to query
* @inode: inode to select the dentry from multiple layers (can be NULL)
- * @open_flags: open flags to control copy-up behavior
- * @flags: flags to control what is returned by this function
+ * @flags: control copy-up and what is returned by this function
*
* If dentry is on a union/overlay, then return the underlying, real dentry.
* Otherwise return the dentry itself.
*
+ * When opening, check flags to see if file needs to be copied up. If O_UPPER
+ * is given, then return upper dentry or NULL.
+ *
* See also: Documentation/filesystems/vfs.txt
*/
static inline struct dentry *d_real(struct dentry *dentry,
const struct inode *inode,
- unsigned int open_flags, unsigned int flags)
+ unsigned int flags)
{
if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
- return dentry->d_op->d_real(dentry, inode, open_flags, flags);
+ return dentry->d_op->d_real(dentry, inode, flags);
else
return dentry;
}
@@ -597,7 +596,7 @@ static inline struct dentry *d_real(stru
static inline struct inode *d_real_inode(const struct dentry *dentry)
{
/* This usage of d_real() results in const dentry */
- return d_backing_inode(d_real((struct dentry *) dentry, NULL, 0, 0));
+ return d_backing_inode(d_real((struct dentry *) dentry, NULL, 0));
}
struct name_snapshot {
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1235,7 +1235,7 @@ static inline struct inode *file_inode(c
static inline struct dentry *file_dentry(const struct file *file)
{
- return d_real(file->f_path.dentry, file_inode(file), 0, 0);
+ return d_real(file->f_path.dentry, file_inode(file), 0);
}
static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -10,6 +10,17 @@
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE)
+/*
+ * This is an internal flag currently used by d_real() to return the upper
+ * dentry of an overlayfs.
+ */
+#define O_UPPER 0x80000000
+
+#if O_UPPER & VALID_OPEN_FLAGS
+#error O_UPPER conflicts with some other open flag
+#endif
+
+
#ifndef force_o_largefile
#define force_o_largefile() (BITS_PER_LONG != 32)
#endif
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