Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752524AbdHRNSZ (ORCPT ); Fri, 18 Aug 2017 09:18:25 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55716 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752928AbdHRNPy (ORCPT ); Fri, 18 Aug 2017 09:15:54 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Al Viro" Date: Fri, 18 Aug 2017 14:13:20 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 128/134] dentry name snapshots In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6843 Lines: 236 3.16.47-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit 49d31c2f389acfe83417083e1208422b4091cd9e upstream. take_dentry_name_snapshot() takes a safe snapshot of dentry name; if the name is a short one, it gets copied into caller-supplied structure, otherwise an extra reference to external name is grabbed (those are never modified). In either case the pointer to stable string is stored into the same structure. dentry must be held by the caller of take_dentry_name_snapshot(), but may be freely dropped afterwards - the snapshot will stay until destroyed by release_dentry_name_snapshot(). Intended use: struct name_snapshot s; take_dentry_name_snapshot(&s, dentry); ... access s.name ... release_dentry_name_snapshot(&s); Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name to pass down with event. Signed-off-by: Al Viro [carnil: backport 4.9: adjust context] [bwh: Backported to 3.16: - External names are not ref-counted, so copy them - Adjust context] Signed-off-by: Ben Hutchings --- --- a/fs/dcache.c +++ b/fs/dcache.c @@ -244,6 +244,43 @@ static void __d_free(struct rcu_head *he kmem_cache_free(dentry_cache, dentry); } +void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry) +{ + spin_lock(&dentry->d_lock); + if (unlikely(dname_external(dentry))) { + u32 len; + char *p; + + for (;;) { + len = dentry->d_name.len; + spin_unlock(&dentry->d_lock); + + p = kmalloc(len + 1, GFP_KERNEL | __GFP_NOFAIL); + + spin_lock(&dentry->d_lock); + if (dentry->d_name.len <= len) + break; + kfree(p); + } + memcpy(p, dentry->d_name.name, dentry->d_name.len + 1); + spin_unlock(&dentry->d_lock); + + name->name = p; + } else { + memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN); + spin_unlock(&dentry->d_lock); + name->name = name->inline_name; + } +} +EXPORT_SYMBOL(take_dentry_name_snapshot); + +void release_dentry_name_snapshot(struct name_snapshot *name) +{ + if (unlikely(name->name != name->inline_name)) + kfree(name->name); +} +EXPORT_SYMBOL(release_dentry_name_snapshot); + static void dentry_free(struct dentry *dentry) { WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias)); --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -620,7 +620,7 @@ struct dentry *debugfs_rename(struct den { int error; struct dentry *dentry = NULL, *trap; - const char *old_name; + struct name_snapshot old_name; trap = lock_rename(new_dir, old_dir); /* Source or destination directories don't exist? */ @@ -635,19 +635,19 @@ struct dentry *debugfs_rename(struct den if (IS_ERR(dentry) || dentry == trap || dentry->d_inode) goto exit; - old_name = fsnotify_oldname_init(old_dentry->d_name.name); + take_dentry_name_snapshot(&old_name, old_dentry); error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode, dentry); if (error) { - fsnotify_oldname_free(old_name); + release_dentry_name_snapshot(&old_name); goto exit; } d_move(old_dentry, dentry); - fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name, + fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name.name, S_ISDIR(old_dentry->d_inode->i_mode), NULL, old_dentry); - fsnotify_oldname_free(old_name); + release_dentry_name_snapshot(&old_name); unlock_rename(new_dir, old_dir); dput(dentry); return old_dentry; --- a/fs/namei.c +++ b/fs/namei.c @@ -4082,11 +4082,11 @@ int vfs_rename(struct inode *old_dir, st { int error; bool is_dir = d_is_dir(old_dentry); - const unsigned char *old_name; struct inode *source = old_dentry->d_inode; struct inode *target = new_dentry->d_inode; bool new_is_dir = false; unsigned max_links = new_dir->i_sb->s_max_links; + struct name_snapshot old_name; if (source == target) return 0; @@ -4136,7 +4136,7 @@ int vfs_rename(struct inode *old_dir, st if (error) return error; - old_name = fsnotify_oldname_init(old_dentry->d_name.name); + take_dentry_name_snapshot(&old_name, old_dentry); dget(new_dentry); if (!is_dir || (flags & RENAME_EXCHANGE)) lock_two_nondirectories(source, target); @@ -4195,14 +4195,14 @@ out: mutex_unlock(&target->i_mutex); dput(new_dentry); if (!error) { - fsnotify_move(old_dir, new_dir, old_name, is_dir, + fsnotify_move(old_dir, new_dir, old_name.name, is_dir, !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); if (flags & RENAME_EXCHANGE) { fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, new_is_dir, NULL, new_dentry); } } - fsnotify_oldname_free(old_name); + release_dentry_name_snapshot(&old_name); return error; } --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -105,16 +105,20 @@ int __fsnotify_parent(struct path *path, if (unlikely(!fsnotify_inode_watches_children(p_inode))) __fsnotify_update_child_dentry_flags(p_inode); else if (p_inode->i_fsnotify_mask & mask) { + struct name_snapshot name; + /* we are notifying a parent so come up with the new mask which * specifies these are events which came from a child. */ mask |= FS_EVENT_ON_CHILD; + take_dentry_name_snapshot(&name, dentry); if (path) ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH, - dentry->d_name.name, 0); + name.name, 0); else ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE, - dentry->d_name.name, 0); + name.name, 0); + release_dentry_name_snapshot(&name); } dput(parent); --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -530,4 +530,11 @@ static inline struct dentry *d_backing_d return upper; } +struct name_snapshot { + const char *name; + char inline_name[DNAME_INLINE_LEN]; +}; +void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); +void release_dentry_name_snapshot(struct name_snapshot *); + #endif /* __LINUX_DCACHE_H */ --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -310,35 +310,4 @@ static inline void fsnotify_change(struc } } -#if defined(CONFIG_FSNOTIFY) /* notify helpers */ - -/* - * fsnotify_oldname_init - save off the old filename before we change it - */ -static inline const unsigned char *fsnotify_oldname_init(const unsigned char *name) -{ - return kstrdup(name, GFP_KERNEL); -} - -/* - * fsnotify_oldname_free - free the name we got from fsnotify_oldname_init - */ -static inline void fsnotify_oldname_free(const unsigned char *old_name) -{ - kfree(old_name); -} - -#else /* CONFIG_FSNOTIFY */ - -static inline const char *fsnotify_oldname_init(const unsigned char *name) -{ - return NULL; -} - -static inline void fsnotify_oldname_free(const unsigned char *old_name) -{ -} - -#endif /* CONFIG_FSNOTIFY */ - #endif /* _LINUX_FS_NOTIFY_H */