Commit 0b671301 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 46b9f8e1

fs/nfs/read.c

+69 −71
Original line number Diff line number Diff line
@@ -460,6 +460,55 @@ nfs_pagein_list(struct list_head *head, int rpages) 
	return error;

}



/*

 * 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.

 */
@@ -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)

		if (nfs_readpage_retry(task, data) != 0)

			return;

	}

	while (!list_empty(&data->pages)) {

		struct nfs_page *req = nfs_list_entry(data->pages.next);
@@ -555,50 +597,6 @@ static const struct rpc_call_ops nfs_read_full_ops = { 
	.rpc_release = nfs_readdata_release,

};



/*

 * 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: