diff options
Diffstat (limited to 'fs/dcache.c')
| -rw-r--r-- | fs/dcache.c | 76 |
1 files changed, 51 insertions, 25 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index c932ed32c77b..1bd4614ce93b 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -90,8 +90,8 @@ static struct kmem_cache *dentry_cache __read_mostly; /** * read_seqbegin_or_lock - begin a sequence number check or locking block - * lock: sequence lock - * seq : sequence number to be checked + * @lock: sequence lock + * @seq : sequence number to be checked * * First try it once optimistically without taking the lock. If that fails, * take the lock. The sequence number is also used as a marker for deciding @@ -103,7 +103,7 @@ static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq) if (!(*seq & 1)) /* Even */ *seq = read_seqbegin(lock); else /* Odd */ - write_seqlock(lock); + read_seqlock_excl(lock); } static inline int need_seqretry(seqlock_t *lock, int seq) @@ -114,7 +114,7 @@ static inline int need_seqretry(seqlock_t *lock, int seq) static inline void done_seqretry(seqlock_t *lock, int seq) { if (seq & 1) - write_sequnlock(lock); + read_sequnlock_excl(lock); } /* @@ -2753,9 +2753,9 @@ static int prepend(char **buffer, int *buflen, const char *str, int namelen) /** * prepend_name - prepend a pathname in front of current buffer pointer - * buffer: buffer pointer - * buflen: allocated length of the buffer - * name: name string and length qstr structure + * @buffer: buffer pointer + * @buflen: allocated length of the buffer + * @name: name string and length qstr structure * * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to * make sure that either the old or the new name pointer and length are @@ -2793,14 +2793,15 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name) * @buffer: pointer to the end of the buffer * @buflen: pointer to buffer length * - * The function tries to write out the pathname without taking any lock other - * than the RCU read lock to make sure that dentries won't go away. It only - * checks the sequence number of the global rename_lock as any change in the - * dentry's d_seq will be preceded by changes in the rename_lock sequence - * number. If the sequence number had been change, it will restart the whole - * pathname back-tracing sequence again. It performs a total of 3 trials of - * lockless back-tracing sequences before falling back to take the - * rename_lock. + * The function will first try to write out the pathname without taking any + * lock other than the RCU read lock to make sure that dentries won't go away. + * It only checks the sequence number of the global rename_lock as any change + * in the dentry's d_seq will be preceded by changes in the rename_lock + * sequence number. If the sequence number had been changed, it will restart + * the whole pathname back-tracing sequence again by taking the rename_lock. + * In this case, there is no need to take the RCU read lock as the recursive + * parent pointer references will keep the dentry chain alive as long as no + * rename operation is performed. */ static int prepend_path(const struct path *path, const struct path *root, @@ -2948,6 +2949,16 @@ static int prepend_unreachable(char **buffer, int *buflen) return prepend(buffer, buflen, "(unreachable)", 13); } +static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) +{ + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + *root = fs->root; + } while (read_seqcount_retry(&fs->seq, seq)); +} + /** * d_path - return the path of a dentry * @path: path to report @@ -2980,13 +2991,15 @@ char *d_path(const struct path *path, char *buf, int buflen) if (path->dentry->d_op && path->dentry->d_op->d_dname) return path->dentry->d_op->d_dname(path->dentry, buf, buflen); - get_fs_root(current->fs, &root); + rcu_read_lock(); + get_fs_root_rcu(current->fs, &root); br_read_lock(&vfsmount_lock); error = path_with_deleted(path, &root, &res, &buflen); br_read_unlock(&vfsmount_lock); + rcu_read_unlock(); + if (error < 0) res = ERR_PTR(error); - path_put(&root); return res; } EXPORT_SYMBOL(d_path); @@ -3094,6 +3107,18 @@ Elong: return ERR_PTR(-ENAMETOOLONG); } +static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, + struct path *pwd) +{ + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + *root = fs->root; + *pwd = fs->pwd; + } while (read_seqcount_retry(&fs->seq, seq)); +} + /* * NOTE! The user-level library version returns a * character pointer. The kernel system call just @@ -3116,23 +3141,25 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) { int error; struct path pwd, root; - char *page = (char *) __get_free_page(GFP_USER); + char *page = __getname(); if (!page) return -ENOMEM; - get_fs_root_and_pwd(current->fs, &root, &pwd); + rcu_read_lock(); + get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); error = -ENOENT; br_read_lock(&vfsmount_lock); if (!d_unlinked(pwd.dentry)) { unsigned long len; - char *cwd = page + PAGE_SIZE; - int buflen = PAGE_SIZE; + char *cwd = page + PATH_MAX; + int buflen = PATH_MAX; prepend(&cwd, &buflen, "\0", 1); error = prepend_path(&pwd, &root, &cwd, &buflen); br_read_unlock(&vfsmount_lock); + rcu_read_unlock(); if (error < 0) goto out; @@ -3145,7 +3172,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) } error = -ERANGE; - len = PAGE_SIZE + page - cwd; + len = PATH_MAX + page - cwd; if (len <= size) { error = len; if (copy_to_user(buf, cwd, len)) @@ -3153,12 +3180,11 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) } } else { br_read_unlock(&vfsmount_lock); + rcu_read_unlock(); } out: - path_put(&pwd); - path_put(&root); - free_page((unsigned long) page); + __putname(page); return error; } |