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Subject[PATCH 05/11] fuse: rework fuse_perform_write()
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The patch allocates as many page pointers in fuse_req as needed to cover
interval [pos .. pos+len-1]. Inline helper fuse_wr_pages() is introduced
to hide this cumbersome arithmetic.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
---
fs/fuse/file.c | 13 +++++++++++--
1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a618371..d72d638 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -881,11 +881,19 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
if (!fc->big_writes)
break;
} while (iov_iter_count(ii) && count < fc->max_write &&
- req->num_pages < FUSE_MAX_PAGES_PER_REQ && offset == 0);
+ req->num_pages < req->max_pages && offset == 0);

return count > 0 ? count : err;
}

+static inline unsigned fuse_wr_pages(loff_t pos, size_t len)
+{
+ return min_t(unsigned,
+ ((pos + len - 1) >> PAGE_CACHE_SHIFT) -
+ (pos >> PAGE_CACHE_SHIFT) + 1,
+ FUSE_MAX_PAGES_PER_REQ);
+}
+
static ssize_t fuse_perform_write(struct file *file,
struct address_space *mapping,
struct iov_iter *ii, loff_t pos)
@@ -901,8 +909,9 @@ static ssize_t fuse_perform_write(struct file *file,
do {
struct fuse_req *req;
ssize_t count;
+ unsigned nr_pages = fuse_wr_pages(pos, iov_iter_count(ii));

- req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
+ req = fuse_get_req(fc, nr_pages);
if (IS_ERR(req)) {
err = PTR_ERR(req);
break;


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