From patchwork Thu Jun 18 07:49:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11611579 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3873F13A0 for ; Thu, 18 Jun 2020 07:49:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21B182166E for ; Thu, 18 Jun 2020 07:49:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728200AbgFRHt6 (ORCPT ); Thu, 18 Jun 2020 03:49:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:35866 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726282AbgFRHt6 (ORCPT ); Thu, 18 Jun 2020 03:49:58 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id E2EC7ABF4 for ; Thu, 18 Jun 2020 07:49:55 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v3 1/3] btrfs: add comments for check_can_nocow() and can_nocow_extent() Date: Thu, 18 Jun 2020 15:49:48 +0800 Message-Id: <20200618074950.136553-2-wqu@suse.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200618074950.136553-1-wqu@suse.com> References: <20200618074950.136553-1-wqu@suse.com> MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org These two functions have extra conditions that their callers need to meet, and some not-that-common parameters used for return value. So adding some comments may save reviewers some time. Signed-off-by: Qu Wenruo --- fs/btrfs/file.c | 19 +++++++++++++++++++ fs/btrfs/inode.c | 19 +++++++++++++++++-- 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index fccf5862cd3e..0e4f57fb2737 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1533,6 +1533,25 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages, return ret; } +/* + * Check if we can do nocow write into the range [@pos, @pos + @write_bytes) + * + * This function will flush ordered extents in the range to ensure proper + * nocow checks for (nowait == false) case. + * + * Return >0 and update @write_bytes if we can do nocow write into the range. + * Return 0 if we can't do nocow write. + * Return -EAGAIN if we can't get the needed lock, or for (nowait == true) case, + * there are ordered extents need to be flushed. + * Return <0 for if other error happened. + * + * NOTE: For wait (nowait==false) calls, callers need to release the drew write + * lock of inode->root->snapshot_lock if return value > 0. + * + * @pos: File offset of the range + * @write_bytes: The length of the range to check, also contains the nocow + * writable length if we can do nocow write + */ static noinline int check_can_nocow(struct btrfs_inode *inode, loff_t pos, size_t *write_bytes, bool nowait) { diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 86f7aa377da9..48e16eae7278 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6922,8 +6922,23 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode, } /* - * returns 1 when the nocow is safe, < 1 on error, 0 if the - * block must be cow'd + * Check if we can write into [@offset, @offset + @len) of @inode. + * + * Return >0 and update @len if we can do nocow write into [@offset, @offset + + * @len). + * Return 0 if we can't do nocow write. + * Return <0 if error happened. + * + * NOTE: This only checks the file extents, caller is responsible to wait for + * any ordered extents. + * + * @offset: File offset + * @len: The length to write, will be updated to the nocow writable + * range + * + * @orig_start: (Optional) Return the original file offset of the file extent + * @orig_len: (Optional) Return the original on-disk length of the file extent + * @ram_bytes: (Optional) Return the ram_bytes of the file extent */ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len, u64 *orig_start, u64 *orig_block_len,