ceph: do not carry i_lock for readdir from dcache
We were taking dcache_lock inside of i_lock, which introduces a dependency
not found elsewhere in the kernel, complicationg the vfs locking
scalability work. Since we don't actually need it here anyway, remove
it.
We only need i_lock to test for the I_COMPLETE flag, so be careful to do
so without dcache_lock held.
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 4958252..e0a2dc6 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -95,10 +95,7 @@
*/
static int __dcache_readdir(struct file *filp,
void *dirent, filldir_t filldir)
- __releases(inode->i_lock)
- __acquires(inode->i_lock)
{
- struct inode *inode = filp->f_dentry->d_inode;
struct ceph_file_info *fi = filp->private_data;
struct dentry *parent = filp->f_dentry;
struct inode *dir = parent->d_inode;
@@ -154,7 +151,6 @@
atomic_inc(&dentry->d_count);
spin_unlock(&dcache_lock);
- spin_unlock(&inode->i_lock);
dout(" %llu (%llu) dentry %p %.*s %p\n", di->offset, filp->f_pos,
dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
@@ -172,35 +168,30 @@
} else {
dput(last);
}
- last = NULL;
}
-
- spin_lock(&inode->i_lock);
- spin_lock(&dcache_lock);
-
last = dentry;
if (err < 0)
- goto out_unlock;
+ goto out;
- p = p->prev;
filp->f_pos++;
/* make sure a dentry wasn't dropped while we didn't have dcache_lock */
- if ((ceph_inode(dir)->i_ceph_flags & CEPH_I_COMPLETE))
- goto more;
- dout(" lost I_COMPLETE on %p; falling back to mds\n", dir);
- err = -EAGAIN;
+ if (!ceph_i_test(dir, CEPH_I_COMPLETE)) {
+ dout(" lost I_COMPLETE on %p; falling back to mds\n", dir);
+ err = -EAGAIN;
+ goto out;
+ }
+
+ spin_lock(&dcache_lock);
+ p = p->prev; /* advance to next dentry */
+ goto more;
out_unlock:
spin_unlock(&dcache_lock);
-
- if (last) {
- spin_unlock(&inode->i_lock);
+out:
+ if (last)
dput(last);
- spin_lock(&inode->i_lock);
- }
-
return err;
}
@@ -272,13 +263,13 @@
ceph_snap(inode) != CEPH_SNAPDIR &&
(ci->i_ceph_flags & CEPH_I_COMPLETE) &&
__ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1)) {
+ spin_unlock(&inode->i_lock);
err = __dcache_readdir(filp, dirent, filldir);
- if (err != -EAGAIN) {
- spin_unlock(&inode->i_lock);
+ if (err != -EAGAIN)
return err;
- }
+ } else {
+ spin_unlock(&inode->i_lock);
}
- spin_unlock(&inode->i_lock);
if (fi->dentry) {
err = note_last_dentry(fi, fi->dentry->d_name.name,
fi->dentry->d_name.len);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index e2e9044..1886294 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -400,8 +400,9 @@
struct ceph_inode_info *ci = ceph_inode(inode);
bool r;
- smp_mb();
+ spin_lock(&inode->i_lock);
r = (ci->i_ceph_flags & mask) == mask;
+ spin_unlock(&inode->i_lock);
return r;
}