From f3dbf1c38e665b1a48b0bbb2002f8bc25dfcea42 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 7 Jul 2017 14:51:19 -0400 Subject: [PATCH] BACKPORT: dentry name snapshots 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 [ghackmann@google.com: backported to 3.10: adjust context] Signed-off-by: Greg Hackmann Change-Id: I612e687cbffa1a03107331a6b3f00911ffbebd8e Bug: 63689921 Signed-off-by: Francisco Franco --- fs/dcache.c | 37 +++++++++++++++++++++++++++++++++++++ fs/debugfs/inode.c | 10 +++++----- fs/namei.c | 8 ++++---- fs/notify/fsnotify.c | 8 ++++++-- include/linux/dcache.h | 7 +++++++ include/linux/fsnotify.h | 31 ------------------------------- 6 files changed, 59 insertions(+), 42 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 5d966a817153..2135ae970c52 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -225,6 +225,43 @@ static void d_free(struct dentry *dentry) call_rcu(&dentry->d_u.d_rcu, __d_free); } +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); + /** * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups * @dentry: the target dentry diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index ba92a0a7603b..33f0691bb4d7 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -620,7 +620,7 @@ struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry, { 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 dentry *old_dir, struct dentry *old_dentry, 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; diff --git a/fs/namei.c b/fs/namei.c index 1f061ae37d9e..9a598c109f24 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3240,7 +3240,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, { int error; int is_dir = S_ISDIR(old_dentry->d_inode->i_mode); - const unsigned char *old_name; + struct name_snapshot old_name; if (old_dentry->d_inode == new_dentry->d_inode) return 0; @@ -3259,16 +3259,16 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, if (!old_dir->i_op->rename) return -EPERM; - old_name = fsnotify_oldname_init(old_dentry->d_name.name); + take_dentry_name_snapshot(&old_name, old_dentry); if (is_dir) error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); else error = vfs_rename_other(old_dir,old_dentry,new_dir,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, new_dentry->d_inode, old_dentry); - fsnotify_oldname_free(old_name); + take_dentry_name_snapshot(&old_name, old_dentry); return error; } diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index e5b6db6634d1..6426f4148262 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -105,16 +105,20 @@ int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask) 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); diff --git a/include/linux/dcache.h b/include/linux/dcache.h index bd8896d0349e..70f05f9dc689 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -410,4 +410,11 @@ static inline bool d_is_su(const struct dentry *dentry) extern int sysctl_vfs_cache_pressure; +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 */ diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index a6dfe6944564..1d2d18f6477f 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -308,35 +308,4 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid) } } -#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 */