Commit e52a8250 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: realloc page array 



Writeback caching currently allocates requests with the maximum number of
possible pages, while the actual number of pages per request depends on a
couple of factors that cannot be determined when the request is allocated
(whether page is already under writeback, whether page is contiguous with
previous pages already added to a request).

This patch allows such requests to start with no page allocation (all pages
inline) and grow the page array on demand.

If the max_pages tunable remains the default value, then this will mean
just one allocation that is the same size as before.  If the tunable is
larger, then this adds at most 3 additional memory allocations (which is
generously compensated by the improved performance from the larger
request).

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 5da784cc

fs/fuse/dev.c

+45 −4
Original line number Diff line number Diff line
@@ -54,6 +54,18 @@ static void fuse_request_init(struct fuse_req *req, struct page **pages, 
	__set_bit(FR_PENDING, &req->flags);

}



static struct page **fuse_req_pages_alloc(unsigned int npages, gfp_t flags,

					  struct fuse_page_desc **desc)

{

	struct page **pages;



	pages = kzalloc(npages * (sizeof(struct page *) +

				  sizeof(struct fuse_page_desc)), flags);

	*desc = (void *) pages + npages * sizeof(struct page *);



	return pages;

}



static struct fuse_req *__fuse_request_alloc(unsigned npages, gfp_t flags)

{

	struct fuse_req *req = kmem_cache_zalloc(fuse_req_cachep, flags);
@@ -63,13 +75,12 @@ static struct fuse_req *__fuse_request_alloc(unsigned npages, gfp_t flags) 


		WARN_ON(npages > FUSE_MAX_MAX_PAGES);

		if (npages > FUSE_REQ_INLINE_PAGES) {

			pages = kzalloc(npages * (sizeof(*pages) +

						  sizeof(*page_descs)), flags);

			pages = fuse_req_pages_alloc(npages, flags,

						     &page_descs);

			if (!pages) {

				kmem_cache_free(fuse_req_cachep, req);

				return NULL;

			}

			page_descs = (void *) pages + npages * sizeof(*pages);

		} else if (npages) {

			pages = req->inline_pages;

			page_descs = req->inline_page_descs;
@@ -91,11 +102,41 @@ struct fuse_req *fuse_request_alloc_nofs(unsigned npages) 
	return __fuse_request_alloc(npages, GFP_NOFS);

}



void fuse_request_free(struct fuse_req *req)

static void fuse_req_pages_free(struct fuse_req *req)

{

	if (req->pages != req->inline_pages)

		kfree(req->pages);

}



bool fuse_req_realloc_pages(struct fuse_conn *fc, struct fuse_req *req,

			    gfp_t flags)

{

	struct page **pages;

	struct fuse_page_desc *page_descs;

	unsigned int npages = min_t(unsigned int,

				    max_t(unsigned int, req->max_pages * 2,

					  FUSE_DEFAULT_MAX_PAGES_PER_REQ),

				    fc->max_pages);

	WARN_ON(npages <= req->max_pages);



	pages = fuse_req_pages_alloc(npages, flags, &page_descs);

	if (!pages)

		return false;



	memcpy(pages, req->pages, sizeof(struct page *) * req->max_pages);

	memcpy(page_descs, req->page_descs,

	       sizeof(struct fuse_page_desc) * req->max_pages);

	fuse_req_pages_free(req);

	req->pages = pages;

	req->page_descs = page_descs;

	req->max_pages = npages;



	return true;

}



void fuse_request_free(struct fuse_req *req)

{

	fuse_req_pages_free(req);

	kmem_cache_free(fuse_req_cachep, req);

}

fs/fuse/file.c

+7 −1
Original line number Diff line number Diff line
@@ -1827,7 +1827,13 @@ static int fuse_writepages_fill(struct page *page, 
	     data->orig_pages[req->num_pages - 1]->index + 1 != page->index)) {

		fuse_writepages_send(data);

		data->req = NULL;

	} else if (req && req->num_pages == req->max_pages) {

		if (!fuse_req_realloc_pages(fc, req, GFP_NOFS)) {

			fuse_writepages_send(data);

			req = data->req = NULL;

		}

	}



	err = -ENOMEM;

	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);

	if (!tmp_page)
@@ -1850,7 +1856,7 @@ static int fuse_writepages_fill(struct page *page, 
		struct fuse_inode *fi = get_fuse_inode(inode);



		err = -ENOMEM;

		req = fuse_request_alloc_nofs(fc->max_pages);

		req = fuse_request_alloc_nofs(FUSE_REQ_INLINE_PAGES);

		if (!req) {

			__free_page(tmp_page);

			goto out_unlock;

fs/fuse/fuse_i.h

+4 −0
Original line number Diff line number Diff line
@@ -879,6 +879,10 @@ struct fuse_req *fuse_request_alloc(unsigned npages); 


struct fuse_req *fuse_request_alloc_nofs(unsigned npages);



bool fuse_req_realloc_pages(struct fuse_conn *fc, struct fuse_req *req,

			    gfp_t flags);





/**

 * Free a request

 */

CRA Git | Maintained and supported by SUSTech CRA and CCSE