NFS: Fix asynchronous read error handling

We must always call ->read_done() before we truncate the page data, or
decide to flag an error. The reasons are that
	in NFSv2, ->read_done() is where the eof flag gets set.
	in NFSv3/v4 ->read_done() handles EJUKEBOX-type errors, and
		  v4 state recovery.

However, we need to mark the pages as uptodate before we deal with short
read errors, since we may need to modify the nfs_read_data arguments.

We therefore split the current nfs_readpage_result() into two parts:
nfs_readpage_result(), which calls ->read_done() etc, and
nfs_readpage_retry(), which subsequently handles short reads.

Note: Removing the code that retries in case of a short read also fixes a
bug in nfs_direct_read_result(), which used to return a corrupted number of
bytes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 69 insertions, 71 deletions

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 8b58bbf6e39e..e879ee6e1385 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -461,6 +461,55 @@ nfs_pagein_list(struct list_head *head, int rpages)
 }
 
 /*
+ * This is the callback from RPC telling us whether a reply was
+ * received or some error occurred (timeout or socket shutdown).
+ */
+int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
+{
+        int status;
+
+        dprintk("%s: %4d, (status %d)\n", __FUNCTION__, task->tk_pid,
+                        task->tk_status);
+
+        status = NFS_PROTO(data->inode)->read_done(task, data);
+        if (status != 0)
+                return status;
+
+        nfs_add_stats(data->inode, NFSIOS_SERVERREADBYTES, data->res.count);
+
+        if (task->tk_status == -ESTALE) {
+                set_bit(NFS_INO_STALE, &NFS_FLAGS(data->inode));
+                nfs_mark_for_revalidate(data->inode);
+        }
+        spin_lock(&data->inode->i_lock);
+        NFS_I(data->inode)->cache_validity |= NFS_INO_INVALID_ATIME;
+        spin_unlock(&data->inode->i_lock);
+        return 0;
+}
+
+static int nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)
+{
+        struct nfs_readargs *argp = &data->args;
+        struct nfs_readres *resp = &data->res;
+
+        if (resp->eof || resp->count == argp->count)
+                return 0;
+
+        /* This is a short read! */
+        nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
+        /* Has the server at least made some progress? */
+        if (resp->count == 0)
+                return 0;
+
+        /* Yes, so retry the read at the end of the data */
+        argp->offset += resp->count;
+        argp->pgbase += resp->count;
+        argp->count -= resp->count;
+        rpc_restart_call(task);
+        return -EAGAIN;
+}
+
+/*
  * Handle a read reply that fills part of a page.
  */
 static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)
@@ -469,12 +518,16 @@ static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)
         struct nfs_page *req = data->req;
         struct page *page = req->wb_page;
  
-        if (likely(task->tk_status >= 0))
-                nfs_readpage_truncate_uninitialised_page(data);
-        else
-                SetPageError(page);
         if (nfs_readpage_result(task, data) != 0)
                 return;
+
+        if (likely(task->tk_status >= 0)) {
+                nfs_readpage_truncate_uninitialised_page(data);
+                if (nfs_readpage_retry(task, data) != 0)
+                        return;
+        }
+        if (unlikely(task->tk_status < 0))
+                SetPageError(page);
         if (atomic_dec_and_test(&req->wb_complete)) {
                 if (!PageError(page))
                         SetPageUptodate(page);
@@ -502,25 +555,13 @@ static void nfs_readpage_set_pages_uptodate(struct nfs_read_data *data)
         count += base;
         for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
                 SetPageUptodate(*pages);
-        if (count != 0)
+        if (count == 0)
+                return;
+        /* Was this a short read? */
+        if (data->res.eof || data->res.count == data->args.count)
                 SetPageUptodate(*pages);
 }
 
-static void nfs_readpage_set_pages_error(struct nfs_read_data *data)
-{
-        unsigned int count = data->args.count;
-        unsigned int base = data->args.pgbase;
-        struct page **pages;
-
-        pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
-        base &= ~PAGE_CACHE_MASK;
-        count += base;
-        for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
-                SetPageError(*pages);
-        if (count != 0)
-                SetPageError(*pages);
-}
-
 /*
  * This is the callback from RPC telling us whether a reply was
  * received or some error occurred (timeout or socket shutdown).
@@ -529,19 +570,20 @@ static void nfs_readpage_result_full(struct rpc_task *task, void *calldata)
 {
         struct nfs_read_data *data = calldata;
 
+        if (nfs_readpage_result(task, data) != 0)
+                return;
         /*
-         * Note: nfs_readpage_result may change the values of
+         * Note: nfs_readpage_retry may change the values of
          * data->args. In the multi-page case, we therefore need
-         * to ensure that we call the next nfs_readpage_set_page_uptodate()
-         * first in the multi-page case.
+         * to ensure that we call nfs_readpage_set_pages_uptodate()
+         * first.
          */
         if (likely(task->tk_status >= 0)) {
                 nfs_readpage_truncate_uninitialised_page(data);
                 nfs_readpage_set_pages_uptodate(data);
-        } else
-                nfs_readpage_set_pages_error(data);
-        if (nfs_readpage_result(task, data) != 0)
-                return;
+                if (nfs_readpage_retry(task, data) != 0)
+                        return;
+        }
         while (!list_empty(&data->pages)) {
                 struct nfs_page *req = nfs_list_entry(data->pages.next);
 
@@ -556,50 +598,6 @@ static const struct rpc_call_ops nfs_read_full_ops = {
 };
 
 /*
- * This is the callback from RPC telling us whether a reply was
- * received or some error occurred (timeout or socket shutdown).
- */
-int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
-{
-        struct nfs_readargs *argp = &data->args;
-        struct nfs_readres *resp = &data->res;
-        int status;
-
-        dprintk("NFS: %4d nfs_readpage_result, (status %d)\n",
-                task->tk_pid, task->tk_status);
-
-        status = NFS_PROTO(data->inode)->read_done(task, data);
-        if (status != 0)
-                return status;
-
-        nfs_add_stats(data->inode, NFSIOS_SERVERREADBYTES, resp->count);
-
-        if (task->tk_status < 0) {
-                if (task->tk_status == -ESTALE) {
-                        set_bit(NFS_INO_STALE, &NFS_FLAGS(data->inode));
-                        nfs_mark_for_revalidate(data->inode);
-                }
-        } else if (resp->count < argp->count && !resp->eof) {
-                /* This is a short read! */
-                nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
-                /* Has the server at least made some progress? */
-                if (resp->count != 0) {
-                        /* Yes, so retry the read at the end of the data */
-                        argp->offset += resp->count;
-                        argp->pgbase += resp->count;
-                        argp->count -= resp->count;
-                        rpc_restart_call(task);
-                        return -EAGAIN;
-                }
-                task->tk_status = -EIO;
-        }
-        spin_lock(&data->inode->i_lock);
-        NFS_I(data->inode)->cache_validity |= NFS_INO_INVALID_ATIME;
-        spin_unlock(&data->inode->i_lock);
-        return 0;
-}
-
-/*
  * Read a page over NFS.
  * We read the page synchronously in the following case:
  *  -   The error flag is set for this page. This happens only when a