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fuse: rework fuse_retrieve()

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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>
This commit is contained in:
Maxim Patlasov 2012-10-26 19:48:42 +04:00 committed by Miklos Szeredi
parent b111c8c0e3
commit 4d53dc99ba
1 changed files with 16 additions and 11 deletions
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27
fs/fuse/dev.c
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@ -1577,12 +1577,23 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
unsigned int num;
unsigned int offset;
size_t total_len = 0;
req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
if (IS_ERR(req))
return PTR_ERR(req);
int num_pages;
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);
req->in.h.opcode = FUSE_NOTIFY_REPLY;
req->in.h.nodeid = outarg->nodeid;
@ -1592,14 +1603,8 @@ 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;