From: Ritesh Harjani <riteshh@codeaurora.org>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-block@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 01/33] block: add a lower-level bio_add_page interface
Date: Thu, 17 May 2018 09:48:30 +0530 [thread overview]
Message-ID: <c8993a13-1084-454c-4d58-17a9e6d96f8e@codeaurora.org> (raw)
In-Reply-To: <20180516180503.GA6627@lst.de>
On 5/16/2018 11:35 PM, Christoph Hellwig wrote:
> On Wed, May 16, 2018 at 10:36:14AM +0530, Ritesh Harjani wrote:
>> 1. if bio_full is true that means no space in bio->bio_io_vec[] no?
>> Than how come we are still proceeding ahead with only warning?
>> While originally in bio_add_page we used to return after checking
>> bio_full. Callers can still call __bio_add_page directly right.
>
> I you don't know if the bio is full or not don't use __bio_add_page,
> keep using bio_add_page. The WARN_ON is just a debug tool to catch
> cases where the developer did use it incorrectly.
>
>> 2. IF above is correct why don't we set the bio->bi_max_vecs to the size
>> of the slab instead of keeeping it to nr_iovecs which user requested?
>> (in bio_alloc_bioset)
>
> Because we limit the user to the number that the user requested. Not
> that this patch changes anything about that.
>
>> 3. Could you please help understand why for cloned bio we still allow
>> __bio_add_page to work? why not WARN and return like in original code?
>
> It doesn't work, and I have now added the WARN_ON to deal with any
> incorrect usage.
>
>>> - if (bio->bi_vcnt >= bio->bi_max_vecs)
>>> - return 0;
>> Originally here we were supposed to return and not proceed further.
>> Should __bio_add_page not have similar checks to safeguard crossing
>> the bio_io_vec[] boundary?
>
> No, __bio_add_page is the "I know what I am doing" interface.
>
Thanks for explaining. I guess I missed reading the comment made on top
of function __bio_add_page.
"The caller must ensure that @bio has space for another bvec"
This discussion helped me understand a bit about bios & bio_vec.
Thanks!!
Ritesh
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2018-05-17 4:18 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-09 7:47 stop using buffer heads in xfs and iomap Christoph Hellwig
2018-05-09 7:47 ` [PATCH 01/33] block: add a lower-level bio_add_page interface Christoph Hellwig
2018-05-09 15:12 ` Matthew Wilcox
2018-05-10 6:40 ` Christoph Hellwig
2018-05-10 21:49 ` Andreas Dilger
2018-05-11 6:29 ` Christoph Hellwig
2018-05-15 16:47 ` Jens Axboe
2018-05-10 8:52 ` Ming Lei
2018-05-11 6:24 ` Christoph Hellwig
2018-05-16 5:06 ` Ritesh Harjani
2018-05-16 18:05 ` Christoph Hellwig
2018-05-17 4:18 ` Ritesh Harjani [this message]
2018-05-09 7:47 ` [PATCH 02/33] fs: factor out a __generic_write_end helper Christoph Hellwig
2018-05-09 15:15 ` Matthew Wilcox
2018-05-10 6:40 ` Christoph Hellwig
2018-05-09 7:48 ` [PATCH 03/33] fs: move page_cache_seek_hole_data to iomap.c Christoph Hellwig
2018-05-09 7:48 ` [PATCH 04/33] fs: remove the buffer_unwritten check in page_seek_hole_data Christoph Hellwig
2018-05-17 11:33 ` Andreas Grünbacher
2018-05-09 7:48 ` [PATCH 05/33] fs: use ->is_partially_uptodate in page_cache_seek_hole_data Christoph Hellwig
2018-05-09 7:48 ` [PATCH 06/33] mm: give the 'ret' variable a better name __do_page_cache_readahead Christoph Hellwig
2018-05-09 15:45 ` Matthew Wilcox
2018-05-10 6:41 ` Christoph Hellwig
2018-05-09 7:48 ` [PATCH 07/33] mm: split ->readpages calls to avoid non-contiguous pages lists Christoph Hellwig
2018-05-09 15:46 ` Matthew Wilcox
2018-05-09 7:48 ` [PATCH 08/33] iomap: use __bio_add_page in iomap_dio_zero Christoph Hellwig
2018-05-09 7:48 ` [PATCH 09/33] iomap: add a iomap_sector helper Christoph Hellwig
2018-05-09 7:48 ` [PATCH 10/33] iomap: add an iomap-based bmap implementation Christoph Hellwig
2018-05-09 16:46 ` Darrick J. Wong
2018-05-10 6:42 ` Christoph Hellwig
2018-05-10 15:08 ` Darrick J. Wong
2018-05-11 6:25 ` Christoph Hellwig
2018-05-12 1:56 ` Darrick J. Wong
2018-05-09 7:48 ` [PATCH 11/33] iomap: add an iomap-based readpage and readpages implementation Christoph Hellwig
2018-05-10 1:17 ` Dave Chinner
2018-05-10 6:44 ` Christoph Hellwig
2018-05-09 7:48 ` [PATCH 12/33] xfs: use iomap_bmap Christoph Hellwig
2018-05-09 7:48 ` [PATCH 13/33] xfs: use iomap for blocksize == PAGE_SIZE readpage and readpages Christoph Hellwig
2018-05-09 7:48 ` [PATCH 14/33] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09 7:48 ` [PATCH 15/33] xfs: simplify xfs_aops_discard_page Christoph Hellwig
2018-05-09 7:48 ` [PATCH 16/33] xfs: move locking into xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09 7:48 ` [PATCH 17/33] xfs: make xfs_writepage_map extent map centric Christoph Hellwig
2018-05-09 7:48 ` [PATCH 18/33] xfs: remove the now unused XFS_BMAPI_IGSTATE flag Christoph Hellwig
2018-05-09 7:48 ` [PATCH 19/33] xfs: remove xfs_reflink_find_cow_mapping Christoph Hellwig
2018-05-09 7:48 ` [PATCH 20/33] xfs: remove xfs_reflink_trim_irec_to_next_cow Christoph Hellwig
2018-05-09 7:48 ` [PATCH 21/33] xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly Christoph Hellwig
2018-05-09 7:48 ` [PATCH 22/33] xfs: don't clear imap_valid for a non-uptodate buffers Christoph Hellwig
2018-05-09 7:48 ` [PATCH 23/33] xfs: remove the imap_valid flag Christoph Hellwig
2018-05-09 7:48 ` [PATCH 24/33] xfs: don't look at buffer heads in xfs_add_to_ioend Christoph Hellwig
2018-05-09 7:48 ` [PATCH 25/33] xfs: move all writeback buffer_head manipulation into xfs_map_at_offset Christoph Hellwig
2018-05-09 7:48 ` [PATCH 26/33] xfs: allow writeback on pages without buffer heads Christoph Hellwig
2018-05-09 7:48 ` [PATCH 27/33] xfs: remove xfs_start_page_writeback Christoph Hellwig
2018-05-09 7:48 ` [PATCH 28/33] xfs: refactor the tail of xfs_writepage_map Christoph Hellwig
2018-05-09 7:48 ` [PATCH 29/33] xfs: do not set the page uptodate in xfs_writepage_map Christoph Hellwig
2018-05-09 7:48 ` [PATCH 30/33] iomap: add initial support for writes without buffer heads Christoph Hellwig
2018-05-09 7:48 ` [PATCH 31/33] iomap: add support for sub-pagesize buffered I/O " Christoph Hellwig
2018-05-14 16:00 ` Goldwyn Rodrigues
2018-05-15 7:26 ` Christoph Hellwig
2018-05-15 13:47 ` Goldwyn Rodrigues
2018-05-16 5:46 ` Dave Chinner
2018-05-09 7:48 ` [PATCH 32/33] xfs: add support for sub-pagesize writeback without buffer_heads Christoph Hellwig
2018-05-09 7:48 ` [PATCH 33/33] fs: remove __block_write_begin and iomap_to_bh Christoph Hellwig
2018-05-10 15:13 ` stop using buffer heads in xfs and iomap Darrick J. Wong
2018-05-11 6:22 ` Christoph Hellwig
2018-05-11 6:39 ` Darrick J. Wong
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