diff options
| author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:49:53 +1100 |
|---|---|---|
| committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:50:27 +1100 |
| commit | c28cc36469554dc55540f059fbdc7fa22a2c31fc (patch) | |
| tree | 6b867456be48b8633a2d56a99e00bb3faf9dccc7 /fs/fs_struct.c | |
| parent | 31e6b01f4183ff419a6d1f86177cbf4662347cec (diff) | |
fs: fs_struct use seqlock
Use a seqlock in the fs_struct to enable us to take an atomic copy of the
complete cwd and root paths. Use this in the RCU lookup path to avoid a
thread-shared spinlock in RCU lookup operations.
Multi-threaded apps may now perform path lookups with scalability matching
multi-process apps. Operations such as stat(2) become very scalable for
multi-threaded workload.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'fs/fs_struct.c')
| -rw-r--r-- | fs/fs_struct.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/fs_struct.c b/fs/fs_struct.c index ed45a9cf5f3..60b8531f41c 100644 --- a/fs/fs_struct.c +++ b/fs/fs_struct.c @@ -14,9 +14,11 @@ void set_fs_root(struct fs_struct *fs, struct path *path) struct path old_root; spin_lock(&fs->lock); + write_seqcount_begin(&fs->seq); old_root = fs->root; fs->root = *path; path_get(path); + write_seqcount_end(&fs->seq); spin_unlock(&fs->lock); if (old_root.dentry) path_put(&old_root); @@ -31,9 +33,11 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path) struct path old_pwd; spin_lock(&fs->lock); + write_seqcount_begin(&fs->seq); old_pwd = fs->pwd; fs->pwd = *path; path_get(path); + write_seqcount_end(&fs->seq); spin_unlock(&fs->lock); if (old_pwd.dentry) @@ -52,6 +56,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root) fs = p->fs; if (fs) { spin_lock(&fs->lock); + write_seqcount_begin(&fs->seq); if (fs->root.dentry == old_root->dentry && fs->root.mnt == old_root->mnt) { path_get(new_root); @@ -64,6 +69,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root) fs->pwd = *new_root; count++; } + write_seqcount_end(&fs->seq); spin_unlock(&fs->lock); } task_unlock(p); @@ -88,8 +94,10 @@ void exit_fs(struct task_struct *tsk) int kill; task_lock(tsk); spin_lock(&fs->lock); + write_seqcount_begin(&fs->seq); tsk->fs = NULL; kill = !--fs->users; + write_seqcount_end(&fs->seq); spin_unlock(&fs->lock); task_unlock(tsk); if (kill) @@ -105,6 +113,7 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old) fs->users = 1; fs->in_exec = 0; spin_lock_init(&fs->lock); + seqcount_init(&fs->seq); fs->umask = old->umask; get_fs_root_and_pwd(old, &fs->root, &fs->pwd); } @@ -144,6 +153,7 @@ EXPORT_SYMBOL(current_umask); struct fs_struct init_fs = { .users = 1, .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock), + .seq = SEQCNT_ZERO, .umask = 0022, }; |