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Commit cd52ed35 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent b92dccf6

fs/nfs/file.c

+13 −0
Original line number Diff line number Diff line
@@ -316,6 +316,17 @@ static int nfs_commit_write(struct file *file, struct page *page, unsigned offse 
	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 @@ struct address_space_operations nfs_file_aops = { 
	.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

fs/nfs/pagelist.c

+8 −2
Original line number Diff line number Diff line
@@ -85,6 +85,10 @@ nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, 
	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_page_writeback(struct nfs_page *req) 
 */

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;

	}

}