NFS: Fix a race with PG_private and nfs_release_page()
We don't need to set PG_private for readahead pages, since they never get
unlocked while I/O is in progress. However there is a small race in
nfs_readpage_release() whereby the page may be unlocked, and have
PG_private set.
Fix is to have PG_private set only for the case of writes...
Also fix a bug in nfs_clear_page_writeback(): Don't attempt to clear the
radix_tree tag if we've already deleted the radix tree entry.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d6e076c..106aca3 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -88,7 +88,6 @@
BUG_ON(PagePrivate(page));
BUG_ON(!PageLocked(page));
BUG_ON(page->mapping->host != inode);
- SetPagePrivate(page);
req->wb_offset = offset;
req->wb_pgbase = offset;
req->wb_bytes = count;
@@ -136,9 +135,11 @@
{
struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
- spin_lock(&nfsi->req_lock);
- radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
- spin_unlock(&nfsi->req_lock);
+ if (req->wb_page != NULL) {
+ spin_lock(&nfsi->req_lock);
+ radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
+ spin_unlock(&nfsi->req_lock);
+ }
nfs_unlock_request(req);
}
@@ -153,7 +154,6 @@
{
struct page *page = req->wb_page;
if (page != NULL) {
- ClearPagePrivate(page);
page_cache_release(page);
req->wb_page = NULL;
}
