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Commit efa4c120 authored by Sage Weil's avatar Sage Weil
Browse files

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: default avatarSage Weil <sage@newdream.net>
parent 61413c2f

fs/ceph/dir.c

+16 −25
Original line number Diff line number Diff line
@@ -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 @@ static int __dcache_readdir(struct file *filp, 


	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 @@ static int __dcache_readdir(struct file *filp, 
		} 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;

	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)) {

		err = __dcache_readdir(filp, dirent, filldir);

		if (err != -EAGAIN) {

		spin_unlock(&inode->i_lock);

		err = __dcache_readdir(filp, dirent, filldir);

		if (err != -EAGAIN)

			return err;

		}

	}

	} else {

		spin_unlock(&inode->i_lock);

	}

	if (fi->dentry) {

		err = note_last_dentry(fi, fi->dentry->d_name.name,

				       fi->dentry->d_name.len);

fs/ceph/super.h

+2 −1
Original line number Diff line number Diff line
@@ -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;

}