NFS: Avoid races between writebacks and truncation
Currently, there is no serialisation between NFS asynchronous writebacks
and truncation at the page level due to the fact that nfs_sync_inode()
cannot lock the pages that it is about to write out.
This means that it is possible to be flushing out data (and calling something
like set_page_writeback()) while the page cache is busy evicting the page.
Oops...
Use the hooks provided in try_to_release_page() to ensure that dirty pages
are always written back to storage before we evict them.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 7a79fbe..387809f 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -316,6 +316,17 @@
return status;
}
+static int nfs_invalidate_page(struct page *page, unsigned long offset)
+{
+ /* FIXME: we really should cancel any unstarted writes on this page */
+ return 1;
+}
+
+static int nfs_release_page(struct page *page, gfp_t gfp)
+{
+ return !nfs_wb_page(page->mapping->host, page);
+}
+
struct address_space_operations nfs_file_aops = {
.readpage = nfs_readpage,
.readpages = nfs_readpages,
@@ -324,6 +335,8 @@
.writepages = nfs_writepages,
.prepare_write = nfs_prepare_write,
.commit_write = nfs_commit_write,
+ .invalidatepage = nfs_invalidate_page,
+ .releasepage = nfs_release_page,
#ifdef CONFIG_NFS_DIRECTIO
.direct_IO = nfs_direct_IO,
#endif
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d53857b..d6e076c 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -85,6 +85,10 @@
atomic_set(&req->wb_complete, 0);
req->wb_index = page->index;
page_cache_get(page);
+ 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;
@@ -147,8 +151,10 @@
*/
void nfs_clear_request(struct nfs_page *req)
{
- if (req->wb_page) {
- page_cache_release(req->wb_page);
+ struct page *page = req->wb_page;
+ if (page != NULL) {
+ ClearPagePrivate(page);
+ page_cache_release(page);
req->wb_page = NULL;
}
}