linux-kernel - [PATCH 10/10] afs: Don't invoke the server to read data beyond EOF

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Message-ID: <153356146640.1195.13118526596319391965.stgit@warthog.procyon.org.uk>
Date:   Mon, 06 Aug 2018 14:17:46 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     dhowells@...hat.com, linux-afs@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        matthew@....cx
Subject: [PATCH 10/10] afs: Don't invoke the server to read data beyond EOF

When writing a new page, clear space in the page rather than attempting to
load it from the server if the space is beyond the EOF.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/write.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 6ff0f25836de..7c7a03310f16 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -33,10 +33,21 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 			 loff_t pos, unsigned int len, struct page *page)
 {
 	struct afs_read *req;
+	size_t p;
+	void *data;
 	int ret;
 
 	_enter(",,%llu", (unsigned long long)pos);
 
+	if (pos >= vnode->vfs_inode.i_size) {
+		p = pos & ~PAGE_MASK;
+		ASSERTCMP(p + len, <=, PAGE_SIZE);
+		data = kmap(page);
+		memset(data + p, 0, len);
+		kunmap(page);
+		return 0;
+	}
+
 	req = kzalloc(sizeof(struct afs_read), GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;