[PATCH] fuse: ensure progress in read and write

In direct_io mode, send at least one page per reqest.  Previously it was
possible that reqests with zero data were sent, and hence the read/write
didn't make any progress, resulting in an infinite (though interruptible)
loop.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c989f0e9456..05dedddf428 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -475,7 +475,7 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 
         nbytes = min(nbytes, (unsigned) FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
         npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        npages = min(npages, FUSE_MAX_PAGES_PER_REQ);
+        npages = min(max(npages, 1), FUSE_MAX_PAGES_PER_REQ);
         down_read(&current->mm->mmap_sem);
         npages = get_user_pages(current, current->mm, user_addr, npages, write,
                                 0, req->pages, NULL);
@@ -506,7 +506,6 @@ static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
                 return -EINTR;
 
         while (count) {
-                size_t tmp;
                 size_t nres;
                 size_t nbytes = min(count, nmax);
                 int err = fuse_get_user_pages(req, buf, nbytes, !write);
@@ -514,8 +513,8 @@ static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
                         res = err;
                         break;
                 }
-                tmp = (req->num_pages << PAGE_SHIFT) - req->page_offset;
-                nbytes = min(nbytes, tmp);
+                nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
+                nbytes = min(count, nbytes);
                 if (write)
                         nres = fuse_send_write(req, file, inode, pos, nbytes);
                 else