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 moslty shuffling lines.
The patch also contains one-line fix suggested by Miklos: the loop iterating
over pages from inode mapping should interpret 'offset' as offset in the very
first page only.
---
fs/fuse/dev.c | 26 ++++++++++++++++----------
1 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6e38af5..cf69df3 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1562,13 +1562,24 @@ 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_multipage(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_multipage(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;
@@ -1577,14 +1588,8 @@ 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;
@@ -1596,6 +1601,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct
inode *inode,
req->pages[req->num_pages] = page;
req->num_pages++;
+ offset = 0;
num -= this_num;
total_len += this_num;
index++;
--
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