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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>
This commit is contained in:
Sage Weil 2010-10-18 14:04:31 -07:00
parent 61413c2f59
commit efa4c1206e
2 changed files with 18 additions and 26 deletions
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41
fs/ceph/dir.c
View File

@ -95,10 +95,7 @@ static unsigned fpos_off(loff_t p)
*/
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 @@ more:
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 @@ more:
} 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 @@ static int ceph_readdir(struct file *filp, void *dirent, filldir_t filldir)
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);

3
fs/ceph/super.h
View File

@ -400,8 +400,9 @@ static inline bool ceph_i_test(struct inode *inode, unsigned mask)
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;
}