fuse: optimize __fuse_direct_io()

__fuse_direct_io() allocates fuse-requests by calling fuse_get_req(fc, n). The
patch calculates 'n' based on iov[] array. This is useful because allocating
FUSE_MAX_PAGES_PER_REQ page pointers and descriptors for each fuse request
would be waste of memory in case of iov-s of smaller size.

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

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index b2aa6c21e2094f8f92b0e946c0d73216f2fb3c13..68e10d43bd3f355bdd88489545109d19344aa6e9 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1088,14 +1088,14 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
                return 0;
        }
 
-       while (nbytes < *nbytesp && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
+       while (nbytes < *nbytesp && req->num_pages < req->max_pages) {
                unsigned npages;
                unsigned long user_addr = fuse_get_user_addr(ii);
                unsigned offset = user_addr & ~PAGE_MASK;
                size_t frag_size = fuse_get_frag_size(ii, *nbytesp - nbytes);
                int ret;
 
-               unsigned n = FUSE_MAX_PAGES_PER_REQ - req->num_pages;
+               unsigned n = req->max_pages - req->num_pages;
                frag_size = min_t(size_t, frag_size, n << PAGE_SHIFT);
 
                npages = (frag_size + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
@@ -1131,6 +1131,23 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
        return 0;
 }
 
+static inline int fuse_iter_npages(const struct iov_iter *ii_p)
+{
+       struct iov_iter ii = *ii_p;
+       int npages = 0;
+
+       while (iov_iter_count(&ii) && npages < FUSE_MAX_PAGES_PER_REQ) {
+               unsigned long user_addr = fuse_get_user_addr(&ii);
+               unsigned offset = user_addr & ~PAGE_MASK;
+               size_t frag_size = iov_iter_single_seg_count(&ii);
+
+               npages += (frag_size + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
+               iov_iter_advance(&ii, frag_size);
+       }
+
+       return min(npages, FUSE_MAX_PAGES_PER_REQ);
+}
+
 static ssize_t __fuse_direct_io(struct file *file, const struct iovec *iov,
                                unsigned long nr_segs, size_t count,
                                loff_t *ppos, int write)
@@ -1145,7 +1162,7 @@ static ssize_t __fuse_direct_io(struct file *file, const struct iovec *iov,
 
        iov_iter_init(&ii, iov, nr_segs, count, 0);
 
-       req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
+       req = fuse_get_req(fc, fuse_iter_npages(&ii));
        if (IS_ERR(req))
                return PTR_ERR(req);
 
@@ -1180,7 +1197,7 @@ static ssize_t __fuse_direct_io(struct file *file, const struct iovec *iov,
                        break;
                if (count) {
                        fuse_put_request(fc, req);
-                       req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
+                       req = fuse_get_req(fc, fuse_iter_npages(&ii));
                        if (IS_ERR(req))
                                break;
                }