Commit 4d65c520 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Fix a hang in the writeback path 



Now that the inode scalability patches have been merged, it is no longer
safe to call igrab() under the inode->i_lock.
Now that we no longer call nfs_clear_request() until the nfs_page is
being freed, we know that we are always holding a reference to the
nfs_open_context, which again holds a reference to the path, and so
the inode cannot be freed until the last nfs_page has been removed
from the radix tree and freed.

We can therefore skip the igrab()/iput() altogether.

Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 16c29daf

fs/nfs/pagelist.c

+2 −2
Original line number Diff line number Diff line
@@ -135,14 +135,14 @@ void nfs_clear_page_tag_locked(struct nfs_page *req) 
		nfs_unlock_request(req);

}



/**

/*

 * nfs_clear_request - Free up all resources allocated to the request

 * @req:

 *

 * Release page and open context resources associated with a read/write

 * request after it has completed.

 */

void nfs_clear_request(struct nfs_page *req)

static void nfs_clear_request(struct nfs_page *req)

{

	struct page *page = req->wb_page;

	struct nfs_open_context *ctx = req->wb_context;

fs/nfs/write.c

+3 −10
Original line number Diff line number Diff line
@@ -389,11 +389,8 @@ static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req) 
	spin_lock(&inode->i_lock);

	error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);

	BUG_ON(error);

	if (!nfsi->npages) {

		igrab(inode);

		if (nfs_have_delegation(inode, FMODE_WRITE))

	if (!nfsi->npages && nfs_have_delegation(inode, FMODE_WRITE))

		nfsi->change_attr++;

	}

	set_bit(PG_MAPPED, &req->wb_flags);

	SetPagePrivate(req->wb_page);

	set_page_private(req->wb_page, (unsigned long)req);
@@ -423,10 +420,6 @@ static void nfs_inode_remove_request(struct nfs_page *req) 
	clear_bit(PG_MAPPED, &req->wb_flags);

	radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);

	nfsi->npages--;

	if (!nfsi->npages) {

		spin_unlock(&inode->i_lock);

		iput(inode);

	} else

	spin_unlock(&inode->i_lock);

	nfs_release_request(req);

}

include/linux/nfs_page.h

+0 −1
Original line number Diff line number Diff line
@@ -78,7 +78,6 @@ extern struct nfs_page *nfs_create_request(struct nfs_open_context *ctx, 
					    struct page *page,

					    unsigned int offset,

					    unsigned int count);

extern	void nfs_clear_request(struct nfs_page *req);

extern	void nfs_release_request(struct nfs_page *req);

CRA Git | Maintained and supported by SUSTech CRA and CCSE