linux-kernel - [PATCH 3/3] afs: Avoid endless loop if file is larger than expected

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Message-Id: <20230502163528.1564398-4-dhowells@redhat.com>
Date:   Tue,  2 May 2023 17:35:28 +0100
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     David Howells <dhowells@...hat.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] afs: Avoid endless loop if file is larger than expected

From: Marc Dionne <marc.dionne@...istor.com>

afs_read_dir fetches an amount of data that's based on what the inode
size is thought to be.  If the file on the server is larger than what
was fetched, the code rechecks i_size and retries.  If the local i_size
was not properly updated, this can lead to an endless loop of fetching
i_size from the server and noticing each time that the size is larger on
the server.

If it is known that the remote size is larger than i_size, bump up the
fetch size to that size.

Fixes: f3ddee8dc4e2 ("afs: Fix directory handling")
Signed-off-by: Marc Dionne <marc.dionne@...istor.com>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: linux-afs@...ts.infradead.org
---
 fs/afs/dir.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index f92b9e62d567..4dd97afa536c 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -275,6 +275,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	loff_t i_size;
 	int nr_pages, i;
 	int ret;
+	loff_t remote_size = 0;
 
 	_enter("");
 
@@ -289,6 +290,8 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 
 expand:
 	i_size = i_size_read(&dvnode->netfs.inode);
+	if (i_size < remote_size)
+	    i_size = remote_size;
 	if (i_size < 2048) {
 		ret = afs_bad(dvnode, afs_file_error_dir_small);
 		goto error;
@@ -364,6 +367,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 			 * buffer.
 			 */
 			up_write(&dvnode->validate_lock);
+			remote_size = req->file_size;
 			goto expand;
 		}