From: Maxim Patlasov <mpatlasov@parallels.com>
Date: Fri, 26 Oct 2012 15:48:42 +0000 (+0400)
Subject: fuse: rework fuse_retrieve()
X-Git-Tag: next-20121112~99^2~12
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=dfa74576499c79bf82f0e3721ff3ec977153d8a4;p=karo-tx-linux.git

fuse: rework fuse_retrieve()

The patch reworks fuse_retrieve() to allocate only so many page pointers
as needed. The core part of the patch is the following calculation:

	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

(thanks Miklos for formula). All other changes are mostly shuffling lines.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 915d83b93894..527ffd02538b 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1582,13 +1582,24 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 	unsigned int num;
 	unsigned int offset;
 	size_t total_len = 0;
+	int num_pages;
 
-	req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
+	offset = outarg->offset & ~PAGE_CACHE_MASK;
+	file_size = i_size_read(inode);
+
+	num = outarg->size;
+	if (outarg->offset > file_size)
+		num = 0;
+	else if (outarg->offset + num > file_size)
+		num = file_size - outarg->offset;
+
+	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	num_pages = min(num_pages, FUSE_MAX_PAGES_PER_REQ);
+
+	req = fuse_get_req(fc, num_pages);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
-	offset = outarg->offset & ~PAGE_CACHE_MASK;
-
 	req->in.h.opcode = FUSE_NOTIFY_REPLY;
 	req->in.h.nodeid = outarg->nodeid;
 	req->in.numargs = 2;
@@ -1597,14 +1608,8 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 	req->end = fuse_retrieve_end;
 
 	index = outarg->offset >> PAGE_CACHE_SHIFT;
-	file_size = i_size_read(inode);
-	num = outarg->size;
-	if (outarg->offset > file_size)
-		num = 0;
-	else if (outarg->offset + num > file_size)
-		num = file_size - outarg->offset;
 
-	while (num && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
+	while (num && req->num_pages < num_pages) {
 		struct page *page;
 		unsigned int this_num;