From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id 606426B0390 for ; Mon, 26 Jun 2017 08:15:19 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id y141so47698380qka.13 for ; Mon, 26 Jun 2017 05:15:19 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id o57si10874593qta.56.2017.06.26.05.15.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Jun 2017 05:15:18 -0700 (PDT) From: Ming Lei Subject: [PATCH v2 15/51] btrfs: comment on direct access bvec table Date: Mon, 26 Jun 2017 20:09:58 +0800 Message-Id: <20170626121034.3051-16-ming.lei@redhat.com> In-Reply-To: <20170626121034.3051-1-ming.lei@redhat.com> References: <20170626121034.3051-1-ming.lei@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jens Axboe , Christoph Hellwig , Huang Ying , Andrew Morton , Alexander Viro Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ming Lei , Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba Cc: linux-btrfs@vger.kernel.org Signed-off-by: Ming Lei --- fs/btrfs/compression.c | 4 ++++ fs/btrfs/inode.c | 12 ++++++++++++ 2 files changed, 16 insertions(+) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 2c0b7b57fcd5..5972f74354ca 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -541,6 +541,10 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, /* we need the actual starting offset of this extent in the file */ read_lock(&em_tree->lock); + /* + * It is still safe to retrieve the 1st page of the bio + * in this way after supporting multipage bvec. + */ em = lookup_extent_mapping(em_tree, page_offset(bio->bi_io_vec->bv_page), PAGE_SIZE); diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 4ab02b34f029..7e725d84917b 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8055,6 +8055,12 @@ static void btrfs_retry_endio_nocsum(struct bio *bio) if (bio->bi_status) goto end; + /* + * WARNING: + * + * With multipage bvec, the following way of direct access to + * bvec table is only safe if the bio includes single page. + */ ASSERT(bio->bi_vcnt == 1); io_tree = &BTRFS_I(inode)->io_tree; failure_tree = &BTRFS_I(inode)->io_failure_tree; @@ -8146,6 +8152,12 @@ static void btrfs_retry_endio(struct bio *bio) uptodate = 1; + /* + * WARNING: + * + * With multipage bvec, the following way of direct access to + * bvec table is only safe if the bio includes single page. + */ ASSERT(bio->bi_vcnt == 1); ASSERT(bio->bi_io_vec->bv_len == btrfs_inode_sectorsize(done->inode)); -- 2.9.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org