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Commit 7c190c8b authored by Maxim Patlasov's avatar Maxim Patlasov Committed by Miklos Szeredi
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fuse: optimize fuse_get_user_pages() 



Let fuse_get_user_pages() pack as many iov-s to a single fuse_req as
possible. This is very beneficial in case of iov[] consisting of many
iov-s of relatively small sizes (e.g. PAGE_SIZE).

Signed-off-by: default avatarMaxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent b98d023a

fs/fuse/file.c

+51 −28
Original line number Diff line number Diff line
@@ -1047,29 +1047,37 @@ static void fuse_release_user_pages(struct fuse_req *req, int write) 
	}

}



static inline void fuse_page_descs_length_init(struct fuse_req *req)

static inline void fuse_page_descs_length_init(struct fuse_req *req,

		unsigned index, unsigned nr_pages)

{

	int i;



	for (i = 0; i < req->num_pages; i++)

	for (i = index; i < index + nr_pages; i++)

		req->page_descs[i].length = PAGE_SIZE -

			req->page_descs[i].offset;

}



static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)

{

	return (unsigned long)ii->iov->iov_base + ii->iov_offset;

}



static inline size_t fuse_get_frag_size(const struct iov_iter *ii,

					size_t max_size)

{

	return min(iov_iter_single_seg_count(ii), max_size);

}



static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,

			       size_t *nbytesp, int write)

{

	size_t nbytes = *nbytesp;

	size_t frag_size = min(iov_iter_single_seg_count(ii), nbytes);

	unsigned long user_addr;

	unsigned offset;

	int npages;



	user_addr = (unsigned long)ii->iov->iov_base + ii->iov_offset;

	offset = user_addr & ~PAGE_MASK;

	size_t nbytes = 0;  /* # bytes already packed in req */



	/* Special case for kernel I/O: can copy directly into the buffer */

	if (segment_eq(get_fs(), KERNEL_DS)) {

		unsigned long user_addr = fuse_get_user_addr(ii);

		size_t frag_size = fuse_get_frag_size(ii, *nbytesp);



		if (write)

			req->in.args[1].value = (void *) user_addr;

		else
@@ -1080,30 +1088,45 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii, 
		return 0;

	}



	nbytes = min_t(size_t, frag_size, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);

	npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

	npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);

	npages = get_user_pages_fast(user_addr, npages, !write, req->pages);

	if (npages < 0)

		return npages;

	while (nbytes < *nbytesp && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {

		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;



	req->num_pages = npages;

	req->page_descs[0].offset = offset;

	fuse_page_descs_length_init(req);

		unsigned n = FUSE_MAX_PAGES_PER_REQ - req->num_pages;

		frag_size = min_t(size_t, frag_size, n << PAGE_SHIFT);



		npages = (frag_size + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

		npages = clamp(npages, 1U, n);



		ret = get_user_pages_fast(user_addr, npages, !write,

					  &req->pages[req->num_pages]);

		if (ret < 0)

			return ret;



		npages = ret;

		frag_size = min_t(size_t, frag_size,

				  (npages << PAGE_SHIFT) - offset);

		iov_iter_advance(ii, frag_size);



		req->page_descs[req->num_pages].offset = offset;

		fuse_page_descs_length_init(req, req->num_pages, npages);



		req->num_pages += npages;

		req->page_descs[req->num_pages - 1].length -=

			(npages << PAGE_SHIFT) - offset - frag_size;



		nbytes += frag_size;

	}



	if (write)

		req->in.argpages = 1;

	else

		req->out.argpages = 1;



	nbytes = (req->num_pages << PAGE_SHIFT) - req->page_descs[0].offset;



	if (frag_size < nbytes)

		req->page_descs[req->num_pages - 1].length -=

			nbytes - frag_size;



	*nbytesp = min(frag_size, nbytes);

	iov_iter_advance(ii, *nbytesp);

	*nbytesp = nbytes;



	return 0;

}
@@ -1948,7 +1971,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg, 
	}

	memcpy(req->pages, pages, sizeof(req->pages[0]) * num_pages);

	req->num_pages = num_pages;

	fuse_page_descs_length_init(req);

	fuse_page_descs_length_init(req, 0, req->num_pages);



	/* okay, let's send it to the client */

	req->in.h.opcode = FUSE_IOCTL;