diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-13 00:24:55 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-13 00:24:55 +0400 |
| commit | 68f0d9d92e5430e250f2bd2a1e7a350e880d776a (patch) | |
| tree | 2e416905bafd3e87a6b6eda8837d5fefe143b19b | |
| parent | 3272c544da48f8915a0e34189182aed029bd0f2b (diff) | |
| download | linux-68f0d9d92e5430e250f2bd2a1e7a350e880d776a.tar.xz | |
vfs: make d_path() get the root path under RCU
This avoids the spinlocks and refcounts in the d_path() sequence too
(used by /proc and various other entities). See commit 8b19e34188a3 for
the equivalent getcwd() system call path.
And unlike getcwd(), d_path() doesn't copy the result to user space, so
I don't need to fear _that_ particular bug happening again.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/dcache.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 91e551b5af59..dddc67fed732 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2869,6 +2869,16 @@ 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 @@ -2901,13 +2911,15 @@ 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); |