[PATCH 3/8] NFS: Fix spurious EIO read errors

[Trond Myklebust <trondmy@xxxxxxxxx>]

If the client attempts to read a page, but the read fails due to some
spurious error (e.g. an ACCESS error or a timeout, ...) then we need
to allow other processes to retry.
Also try to report errors correctly when doing a synchronous readpage.

Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
 fs/nfs/read.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index c19841c82b6a..252f31bfd497 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -91,19 +91,25 @@ void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
 }
 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
 
-static void nfs_readpage_release(struct nfs_page *req)
+static void nfs_readpage_release(struct nfs_page *req, int error)
 {
 	struct inode *inode = d_inode(nfs_req_openctx(req)->dentry);
+	struct page *page = req->wb_page;
 
 	dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
 		(unsigned long long)NFS_FILEID(inode), req->wb_bytes,
 		(long long)req_offset(req));
 
+	if (error < 0)
+		SetPageError(page);
 	if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
-		if (PageUptodate(req->wb_page))
-			nfs_readpage_to_fscache(inode, req->wb_page, 0);
+		struct address_space *mapping = page_file_mapping(page);
 
-		unlock_page(req->wb_page);
+		if (PageUptodate(page))
+			nfs_readpage_to_fscache(inode, page, 0);
+		else if (PageError(page) && !PagePrivate(page))
+			generic_error_remove_page(mapping, page);
+		unlock_page(page);
 	}
 	nfs_release_request(req);
 }
@@ -131,7 +137,7 @@ int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 			     &nfs_async_read_completion_ops);
 	if (!nfs_pageio_add_request(&pgio, new)) {
 		nfs_list_remove_request(new);
-		nfs_readpage_release(new);
+		nfs_readpage_release(new, pgio.pg_error);
 	}
 	nfs_pageio_complete(&pgio);
 
@@ -153,6 +159,7 @@ static void nfs_page_group_set_uptodate(struct nfs_page *req)
 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 {
 	unsigned long bytes = 0;
+	int error;
 
 	if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 		goto out;
@@ -179,14 +186,19 @@ static void nfs_read_completion(struct nfs_pgio_header *hdr)
 				zero_user_segment(page, start, end);
 			}
 		}
+		error = 0;
 		bytes += req->wb_bytes;
 		if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 			if (bytes <= hdr->good_bytes)
 				nfs_page_group_set_uptodate(req);
+			else {
+				error = hdr->error;
+				xchg(&nfs_req_openctx(req)->error, error);
+			}
 		} else
 			nfs_page_group_set_uptodate(req);
 		nfs_list_remove_request(req);
-		nfs_readpage_release(req);
+		nfs_readpage_release(req, error);
 	}
 out:
 	hdr->release(hdr);
@@ -213,7 +225,7 @@ nfs_async_read_error(struct list_head *head, int error)
 	while (!list_empty(head)) {
 		req = nfs_list_entry(head->next);
 		nfs_list_remove_request(req);
-		nfs_readpage_release(req);
+		nfs_readpage_release(req, error);
 	}
 }
 
@@ -337,8 +349,13 @@ int nfs_readpage(struct file *file, struct page *page)
 			goto out;
 	}
 
+	xchg(&ctx->error, 0);
 	error = nfs_readpage_async(ctx, inode, page);
-
+	if (!error) {
+		error = wait_on_page_locked_killable(page);
+		if (!PageUptodate(page) && !error)
+			error = xchg(&ctx->error, 0);
+	}
 out:
 	put_nfs_open_context(ctx);
 	return error;
@@ -372,8 +389,8 @@ readpage_async_filler(void *data, struct page *page)
 		zero_user_segment(page, len, PAGE_SIZE);
 	if (!nfs_pageio_add_request(desc->pgio, new)) {
 		nfs_list_remove_request(new);
-		nfs_readpage_release(new);
 		error = desc->pgio->pg_error;
+		nfs_readpage_release(new, error);
 		goto out;
 	}
 	return 0;
-- 
2.21.0