Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751454AbdIOHcg (ORCPT ); Fri, 15 Sep 2017 03:32:36 -0400 Received: from mail-wr0-f194.google.com ([209.85.128.194]:35238 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750838AbdIOHcc (ORCPT ); Fri, 15 Sep 2017 03:32:32 -0400 X-Google-Smtp-Source: ADKCNb6d9BB3PaciModbQThdOrszt3Q+i7P4Gg33hsdCk9mR9Mpfo6VNJPJsTrAhqiBWCv/5vdzyGA== Date: Fri, 15 Sep 2017 09:32:26 +0200 From: Miklos Szeredi To: Linus Torvalds Cc: Al Viro , Linux Kernel Mailing List , linux-fsdevel , "linux-unionfs@vger.kernel.org" Subject: Re: [GIT PULL] overlayfs update for 4.14 Message-ID: <20170915073226.GC19278@veci.piliscsaba.szeredi.hu> References: <20170913140528.GA19278@veci.piliscsaba.szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7564 Lines: 230 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 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 --- 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