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NFS: Fix a hang in the writeback path

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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: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2011-03-25 14:15:11 -04:00
commit 4d65c520fb
3 changed files with 5 additions and 13 deletions
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4
fs/nfs/pagelist.c
View file

@ -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;

9
fs/nfs/write.c
View file

@ -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);
}

1
include/linux/nfs_page.h
View file

@ -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);