Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755309Ab3JBRif (ORCPT ); Wed, 2 Oct 2013 13:38:35 -0400 Received: from relay.parallels.com ([195.214.232.42]:39814 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754951Ab3JBRid (ORCPT ); Wed, 2 Oct 2013 13:38:33 -0400 Subject: [PATCH 2/4] fuse: writepages: crop secondary requests To: miklos@szeredi.hu From: Maxim Patlasov Cc: fuse-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 02 Oct 2013 21:38:32 +0400 Message-ID: <20131002173823.31188.77171.stgit@dhcp-10-30-17-2.sw.ru> In-Reply-To: <20131002173701.31188.33547.stgit@dhcp-10-30-17-2.sw.ru> References: <20131002173701.31188.33547.stgit@dhcp-10-30-17-2.sw.ru> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4288 Lines: 123 If writeback happens while fuse is in FUSE_NOWRITE condition, the request will be queued but not processed immediately (see fuse_flush_writepages()). Until FUSE_NOWRITE becomes relaxed, more writebacks can happen. They will be queued as "secondary" requests to that first ("primary") request. Existing implementation crops only primary request. This is not correct because a subsequent extending write(2) may increase i_size and then secondary requests won't be cropped properly. The result would be stale data written to the server to a file offset where zeros must be. Similar problem may happen if secondary requests are attached to an in-flight request that was already cropped. The patch solves the issue by cropping all secondary requests in fuse_writepage_end(). Thanks to Miklos for idea. Signed-off-by: Maxim Patlasov --- fs/fuse/file.c | 52 +++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 41 insertions(+), 11 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 575e44f..a3c7123 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1435,6 +1435,22 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req) wake_up(&fi->page_waitq); } +/* Returns zero if the request is truncated off completely */ +static inline loff_t fuse_crop_request(struct fuse_req *req, loff_t size) +{ + struct fuse_write_in *inarg = &req->misc.write.in; + __u64 data_size = inarg->size ? : req->num_pages * PAGE_CACHE_SIZE; + + if (inarg->offset + data_size <= size) + inarg->size = data_size; + else if (inarg->offset < size) + inarg->size = size - inarg->offset; + else + return 0; + + return inarg->size; +} + /* Called under fc->lock, may release and reacquire it */ static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req) __releases(fc->lock) @@ -1442,22 +1458,14 @@ __acquires(fc->lock) { struct fuse_inode *fi = get_fuse_inode(req->inode); loff_t size = i_size_read(req->inode); - struct fuse_write_in *inarg = &req->misc.write.in; - __u64 data_size = req->num_pages * PAGE_CACHE_SIZE; if (!fc->connected) goto out_free; - if (inarg->offset + data_size <= size) { - inarg->size = data_size; - } else if (inarg->offset < size) { - inarg->size = size - inarg->offset; - } else { - /* Got truncated off completely */ - goto out_free; - } + req->in.args[1].size = fuse_crop_request(req, size); + if (req->in.args[1].size == 0) + goto out_free; /* Got truncated off completely */ - req->in.args[1].size = inarg->size; fi->writectr++; fuse_request_send_background_locked(fc, req); return; @@ -1495,13 +1503,24 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req) { struct inode *inode = req->inode; struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_req *drop = NULL; mapping_set_error(inode->i_mapping, req->out.h.error); spin_lock(&fc->lock); while (req->misc.write.next) { struct fuse_req *next = req->misc.write.next; + struct fuse_write_in *inarg = &req->misc.write.in; + loff_t size = inarg->offset + inarg->size; + req->misc.write.next = next->misc.write.next; next->misc.write.next = NULL; + + if (fuse_crop_request(next, size) == 0) { + next->misc.write.next = drop; + drop = next; + continue; + } + list_add(&next->writepages_entry, &fi->writepages); list_add_tail(&next->list, &fi->queued_writes); fuse_flush_writepages(inode); @@ -1510,6 +1529,17 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req) fuse_writepage_finish(fc, req); spin_unlock(&fc->lock); fuse_writepage_free(fc, req); + + while (drop) { + struct fuse_req *next = drop->misc.write.next; + struct backing_dev_info *bdi = + drop->inode->i_mapping->backing_dev_info; + dec_bdi_stat(bdi, BDI_WRITEBACK); + dec_zone_page_state(drop->pages[0], NR_WRITEBACK_TEMP); + fuse_writepage_free(fc, drop); + fuse_put_request(fc, drop); + drop = next; + } } static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/