From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miklos Szeredi Subject: Re: [PATCH 10/16] fuse: Implement writepages callback Date: Fri, 19 Jul 2013 18:50:37 +0200 Message-ID: <20130719165037.GA18358@tucsk.piliscsaba.szeredi.hu> References: <20130629172211.20175.70154.stgit@maximpc.sw.ru> <20130629174525.20175.18987.stgit@maximpc.sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: riel@redhat.com, dev@parallels.com, xemul@parallels.com, fuse-devel@lists.sourceforge.net, bfoster@redhat.com, linux-kernel@vger.kernel.org, jbottomley@parallels.com, linux-mm@kvack.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org, fengguang.wu@intel.com, devel@openvz.org, mgorman@suse.de To: Maxim Patlasov Return-path: Content-Disposition: inline In-Reply-To: <20130629174525.20175.18987.stgit@maximpc.sw.ru> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Sat, Jun 29, 2013 at 09:45:29PM +0400, Maxim Patlasov wrote: > From: Pavel Emelyanov > > The .writepages one is required to make each writeback request carry more than > one page on it. The patch enables optimized behaviour unconditionally, > i.e. mmap-ed writes will benefit from the patch even if fc->writeback_cache=0. I rewrote this a bit, so we won't have to do the thing in two passes, which makes it simpler and more robust. Waiting for page writeback here is wrong anyway, see comment above fuse_page_mkwrite(). BTW we had a race there because fuse_page_mkwrite() didn't take the page lock. I've also fixed that up and pushed a series containing these patches up to implementing ->writepages() to git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git writepages Passed some trivial testing but more is needed. I'll get to the rest of the patches next week. Thanks, Miklos Subject: fuse: Implement writepages callback From: Pavel Emelyanov Date: Sat, 29 Jun 2013 21:45:29 +0400 The .writepages one is required to make each writeback request carry more than one page on it. The patch enables optimized behaviour unconditionally, i.e. mmap-ed writes will benefit from the patch even if fc->writeback_cache=0. [SzM: simplify, add comments] Signed-off-by: Maxim Patlasov Signed-off-by: Miklos Szeredi --- fs/fuse/file.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 139 insertions(+) --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1579,6 +1579,144 @@ static int fuse_writepage(struct page *p return err; } +struct fuse_fill_wb_data { + struct fuse_req *req; + struct fuse_file *ff; + struct inode *inode; +}; + +static void fuse_writepages_send(struct fuse_fill_wb_data *data) +{ + struct fuse_req *req = data->req; + struct inode *inode = data->inode; + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_inode *fi = get_fuse_inode(inode); + + req->ff = fuse_file_get(data->ff); + spin_lock(&fc->lock); + list_add_tail(&req->list, &fi->queued_writes); + fuse_flush_writepages(inode); + spin_unlock(&fc->lock); +} + +static int fuse_writepages_fill(struct page *page, + struct writeback_control *wbc, void *_data) +{ + struct fuse_fill_wb_data *data = _data; + struct fuse_req *req = data->req; + struct inode *inode = data->inode; + struct fuse_conn *fc = get_fuse_conn(inode); + struct page *tmp_page; + int err; + + if (req) { + BUG_ON(!req->num_pages); + if (req->num_pages == FUSE_MAX_PAGES_PER_REQ || + (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_write || + req->pages[req->num_pages - 1]->index + 1 != page->index) { + + fuse_writepages_send(data); + data->req = NULL; + } + } + err = -ENOMEM; + tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM); + if (!tmp_page) + goto out_unlock; + + /* + * The page must not be redirtied until the writeout is completed + * (i.e. userspace has sent a reply to the write request). Otherwise + * there could be more than one temporary page instance for each real + * page. + * + * This is ensured by holding the page lock in page_mkwrite() while + * checking fuse_page_is_writeback(). We already hold the page lock + * since clear_page_dirty_for_io() and keep it held until we add the + * request to the fi->writepages list and increment req->num_pages. + * After this fuse_page_is_writeback() will indicate that the page is + * under writeback, so we can release the page lock. + */ + if (data->req == NULL) { + struct fuse_inode *fi = get_fuse_inode(inode); + + err = -ENOMEM; + req = fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ); + if (!req) { + __free_page(tmp_page); + goto out_unlock; + } + + fuse_write_fill(req, data->ff, page_offset(page), 0); + req->misc.write.in.write_flags |= FUSE_WRITE_CACHE; + req->in.argpages = 1; + req->background = 1; + req->num_pages = 0; + req->end = fuse_writepage_end; + req->inode = inode; + + spin_lock(&fc->lock); + list_add(&req->writepages_entry, &fi->writepages); + spin_unlock(&fc->lock); + + data->req = req; + } + set_page_writeback(page); + + copy_highpage(tmp_page, page); + req->pages[req->num_pages] = tmp_page; + req->page_descs[req->num_pages].offset = 0; + req->page_descs[req->num_pages].length = PAGE_SIZE; + + inc_bdi_stat(page->mapping->backing_dev_info, BDI_WRITEBACK); + inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); + end_page_writeback(page); + + /* + * Protected by fc->lock against concurrent access by + * fuse_page_is_writeback(). + */ + spin_lock(&fc->lock); + req->num_pages++; + spin_unlock(&fc->lock); + + err = 0; +out_unlock: + unlock_page(page); + + return err; +} + +static int fuse_writepages(struct address_space *mapping, + struct writeback_control *wbc) +{ + struct inode *inode = mapping->host; + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_fill_wb_data data; + int err; + + err = -EIO; + if (is_bad_inode(inode)) + goto out; + + data.req = NULL; + data.inode = inode; + data.ff = fuse_write_file(fc, get_fuse_inode(inode)); + if (!data.ff) + goto out; + + err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data); + if (data.req) { + /* Ignore errors if we can write at least one page */ + BUG_ON(!data.req->num_pages); + fuse_writepages_send(&data); + err = 0; + } + fuse_file_put(data.ff, false); +out: + return err; +} + static int fuse_launder_page(struct page *page) { int err = 0; @@ -2589,6 +2727,7 @@ static const struct file_operations fuse static const struct address_space_operations fuse_file_aops = { .readpage = fuse_readpage, .writepage = fuse_writepage, + .writepages = fuse_writepages, .launder_page = fuse_launder_page, .readpages = fuse_readpages, .set_page_dirty = __set_page_dirty_nobuffers, -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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