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/namei.c | |
| parent | fs: rcu-walk for path lookup (diff) | |
| download | linux-dev-c28cc36469554dc55540f059fbdc7fa22a2c31fc.tar.xz linux-dev-c28cc36469554dc55540f059fbdc7fa22a2c31fc.zip | |
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/namei.c')
| -rw-r--r-- | fs/namei.c | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/fs/namei.c b/fs/namei.c index 8d3f15b3a541..c731b50a6184 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -684,9 +684,12 @@ static __always_inline void set_root_rcu(struct nameidata *nd) { if (!nd->root.mnt) { struct fs_struct *fs = current->fs; - spin_lock(&fs->lock); - nd->root = fs->root; - spin_unlock(&fs->lock); + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + nd->root = fs->root; + } while (read_seqcount_retry(&fs->seq, seq)); } } @@ -1369,26 +1372,31 @@ static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct n if (*name=='/') { struct fs_struct *fs = current->fs; + unsigned seq; br_read_lock(vfsmount_lock); rcu_read_lock(); - spin_lock(&fs->lock); - nd->root = fs->root; - nd->path = nd->root; - nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); - spin_unlock(&fs->lock); + do { + seq = read_seqcount_begin(&fs->seq); + nd->root = fs->root; + nd->path = nd->root; + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } while (read_seqcount_retry(&fs->seq, seq)); } else if (dfd == AT_FDCWD) { struct fs_struct *fs = current->fs; + unsigned seq; br_read_lock(vfsmount_lock); rcu_read_lock(); - spin_lock(&fs->lock); - nd->path = fs->pwd; - nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); - spin_unlock(&fs->lock); + do { + seq = read_seqcount_begin(&fs->seq); + nd->path = fs->pwd; + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } while (read_seqcount_retry(&fs->seq, seq)); + } else { struct dentry *dentry; @@ -1411,7 +1419,7 @@ static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct n if (fput_needed) nd->file = file; - nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); br_read_lock(vfsmount_lock); rcu_read_lock(); } |