Commit ba512c1b authored by Dave Wysochanski's avatar Dave Wysochanski Committed by Trond Myklebust
Browse files

NFS: Fix fscache read from NFS after cache error 

Earlier commits refactored some NFS read code and removed
nfs_readpage_async(), but neglected to properly fixup
nfs_readpage_from_fscache_complete().  The code path is
only hit when something unusual occurs with the cachefiles
backing filesystem, such as an IO error or while a cookie
is being invalidated.

Mark page with PG_checked if fscache IO completes in error,
unlock the page, and let the VM decide to re-issue based on
PG_uptodate.  When the VM reissues the readpage, PG_checked
allows us to skip over fscache and read from the server.

Link: https://marc.info/?l=linux-nfs&m=162498209518739


Fixes: 1e83b173 ("NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async()")
Signed-off-by: default avatarDave Wysochanski <dwysocha@redhat.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent e0340f16

fs/nfs/fscache.c

+13 −5
Original line number Diff line number Diff line
@@ -385,13 +385,16 @@ static void nfs_readpage_from_fscache_complete(struct page *page, 
		 "NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",

		 page, context, error);



	/* if the read completes with an error, we just unlock the page and let

	 * the VM reissue the readpage */

	if (!error) {

	/*

	 * If the read completes with an error, mark the page with PG_checked,

	 * unlock the page, and let the VM reissue the readpage.

	 */

	if (!error)

		SetPageUptodate(page);

	else

		SetPageChecked(page);

	unlock_page(page);

}

}



/*

 * Retrieve a page from fscache
@@ -405,6 +408,11 @@ int __nfs_readpage_from_fscache(struct nfs_open_context *ctx, 
		 "NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",

		 nfs_i_fscache(inode), page, page->index, page->flags, inode);



	if (PageChecked(page)) {

		ClearPageChecked(page);

		return 1;

	}



	ret = fscache_read_or_alloc_page(nfs_i_fscache(inode),

					 page,

					 nfs_readpage_from_fscache_complete,

fs/nfs/read.c

+3 −2
Original line number Diff line number Diff line
@@ -362,13 +362,13 @@ int nfs_readpage(struct file *file, struct page *page) 
	} else

		desc.ctx = get_nfs_open_context(nfs_file_open_context(file));



	xchg(&desc.ctx->error, 0);

	if (!IS_SYNC(inode)) {

		ret = nfs_readpage_from_fscache(desc.ctx, inode, page);

		if (ret == 0)

			goto out;

			goto out_wait;

	}



	xchg(&desc.ctx->error, 0);

	nfs_pageio_init_read(&desc.pgio, inode, false,

			     &nfs_async_read_completion_ops);
@@ -378,6 +378,7 @@ int nfs_readpage(struct file *file, struct page *page) 


	nfs_pageio_complete_read(&desc.pgio);

	ret = desc.pgio.pg_error < 0 ? desc.pgio.pg_error : 0;

out_wait:

	if (!ret) {

		ret = wait_on_page_locked_killable(page);

		if (!PageUptodate(page) && !ret)