diff options
| author | NeilBrown <neilb@suse.de> | 2014-10-13 15:52:14 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-14 02:18:16 +0200 |
| commit | 23bfc2a24ea3d993cc5cc90c9970654e7232502e (patch) | |
| tree | a2bc0e834578b8b8559e255363e9b95d08158e97 /fs/autofs4/expire.c | |
| parent | 8a273345dcb1d74d12f28a0a76320b23e7e32f55 (diff) | |
autofs4: allow RCU-walk to walk through autofs4
This series teaches autofs about RCU-walk so that we don't drop straight
into REF-walk when we hit an autofs directory, and so that we avoid
spinlocks as much as possible when performing an RCU-walk.
This is needed so that the benefits of the recent NFS support for
RCU-walk are fully available when NFS filesystems are automounted.
Patches have been carefully reviewed and tested both with test suites
and in production - thanks a lot to Ian Kent for his support there.
This patch (of 6):
Any attempt to look up a pathname that passes though an autofs4 mount is
currently forced out of RCU-walk into REF-walk.
This can significantly hurt performance of many-thread work loads on
many-core systems, especially if the automounted filesystem supports
RCU-walk but doesn't get to benefit from it.
So if autofs4_d_manage is called with rcu_walk set, only fail with -ECHILD
if it is necessary to wait longer than a spinlock.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Ian Kent <raven@themaw.net>
Tested-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/autofs4/expire.c')
| -rw-r--r-- | fs/autofs4/expire.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c index 8fa3895cda02..1695eda8ac18 100644 --- a/fs/autofs4/expire.c +++ b/fs/autofs4/expire.c @@ -461,7 +461,7 @@ found: return expired; } -int autofs4_expire_wait(struct dentry *dentry) +int autofs4_expire_wait(struct dentry *dentry, int rcu_walk) { struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); struct autofs_info *ino = autofs4_dentry_ino(dentry); @@ -471,6 +471,8 @@ int autofs4_expire_wait(struct dentry *dentry) spin_lock(&sbi->fs_lock); if (ino->flags & AUTOFS_INF_EXPIRING) { spin_unlock(&sbi->fs_lock); + if (rcu_walk) + return -ECHILD; DPRINTK("waiting for expire %p name=%.*s", dentry, dentry->d_name.len, dentry->d_name.name); |