From: Christoph Hellwig <hch@lst.de>
To: Brian Foster <bfoster@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 23/24] iomap: add support for sub-pagesize buffered I/O without buffer heads
Date: Wed, 20 Jun 2018 09:56:55 +0200 [thread overview]
Message-ID: <20180620075655.GA2668@lst.de> (raw)
In-Reply-To: <20180619165211.GD2806@bfoster>
On Tue, Jun 19, 2018 at 12:52:11PM -0400, Brian Foster wrote:
> > + /*
> > + * Move the caller beyond our range so that it keeps making progress.
> > + * For that we have to include any leading non-uptodate ranges, but
>
> Do you mean "leading uptodate ranges" here? E.g., pos is pushed forward
> past those ranges we don't have to read, so (pos - orig_pos) reflects
> the initial uptodate range while plen reflects the length we have to
> read..?
Yes.
> > +
> > + do {
>
> Kind of a nit, but this catches my eye and manages to confuse me every
> time I look at it. A comment along the lines of:
>
> /*
> * Pass in the block aligned start/end so we get back block
> * aligned/adjusted poff/plen and can compare with unaligned
> * from/to below.
> */
>
> ... would be nice here, IMO.
Fine with me.
> > + iomap_adjust_read_range(inode, iop, &block_start,
> > + block_end - block_start, &poff, &plen);
> > + if (plen == 0)
> > + break;
> > +
> > + if ((from > poff && from < poff + plen) ||
> > + (to > poff && to < poff + plen)) {
> > + status = iomap_read_page_sync(inode, block_start, page,
> > + poff, plen, from, to, iomap);
>
> After taking another look at the buffer head path, it does look like we
> have slightly different behavior here. IIUC, the former reads only the
> !uptodate blocks that fall along the from/to boundaries. Here, if say
> from = 1, to = PAGE_SIZE and the page is fully !uptodate, it looks like
> we'd read the entire page worth of blocks (assuming contiguous 512b
> blocks, for example). Intentional? Doesn't seem like a big deal, but
> could be worth a followup fix.
It wasn't actuall intentional, but I actually think it is the right thing
in then end, as it means we'll often do a single read instead of two
separate ones.
next prev parent reply other threads:[~2018-06-20 8:26 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-15 13:01 stop using buffer heads in xfs v6 Christoph Hellwig
2018-06-15 13:01 ` [PATCH 01/24] iomap: add an iomap-based readpage and readpages implementation Christoph Hellwig
2018-06-29 14:44 ` [PATCH] iomap: Add inline data support to iomap_readpage_actor Andreas Gruenbacher
2018-07-01 6:21 ` Christoph Hellwig
2018-07-01 21:43 ` Andreas Gruenbacher
2018-07-02 12:52 ` Christoph Hellwig
2018-07-02 15:05 ` Andreas Gruenbacher
2018-06-15 13:01 ` [PATCH 02/24] xfs: use iomap for blocksize == PAGE_SIZE readpage and readpages Christoph Hellwig
2018-06-15 13:01 ` [PATCH 03/24] iomap: add initial support for writes without buffer heads Christoph Hellwig
2018-06-15 13:01 ` [PATCH 04/24] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-06-15 13:01 ` [PATCH 05/24] xfs: simplify xfs_aops_discard_page Christoph Hellwig
2018-06-15 13:01 ` [PATCH 06/24] xfs: move locking into xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-06-19 5:26 ` Darrick J. Wong
2018-06-15 13:01 ` [PATCH 07/24] xfs: do not set the page uptodate in xfs_writepage_map Christoph Hellwig
2018-06-15 13:01 ` [PATCH 08/24] xfs: don't clear imap_valid for a non-uptodate buffers Christoph Hellwig
2018-06-15 13:01 ` [PATCH 09/24] xfs: don't use XFS_BMAPI_IGSTATE in xfs_map_blocks Christoph Hellwig
2018-06-19 5:27 ` Darrick J. Wong
2018-06-15 13:01 ` [PATCH 10/24] xfs: remove xfs_reflink_trim_irec_to_next_cow Christoph Hellwig
2018-06-19 5:30 ` Darrick J. Wong
2018-06-15 13:01 ` [PATCH 11/24] xfs: remove xfs_map_cow Christoph Hellwig
2018-06-18 17:38 ` Brian Foster
2018-06-19 5:35 ` Darrick J. Wong
2018-06-19 16:53 ` Christoph Hellwig
2018-06-20 0:37 ` Darrick J. Wong
2018-06-15 13:01 ` [PATCH 12/24] xfs: rename the offset variable in xfs_writepage_map Christoph Hellwig
2018-06-19 5:37 ` Darrick J. Wong
2018-06-15 13:01 ` [PATCH 13/24] xfs: make xfs_writepage_map extent map centric Christoph Hellwig
2018-06-18 17:38 ` Brian Foster
2018-06-19 5:43 ` Darrick J. Wong
2018-06-19 16:52 ` Christoph Hellwig
2018-06-15 13:01 ` [PATCH 14/24] xfs: remove the now unused XFS_BMAPI_IGSTATE flag Christoph Hellwig
2018-06-15 13:02 ` [PATCH 15/24] xfs: remove xfs_reflink_find_cow_mapping Christoph Hellwig
2018-06-15 13:02 ` [PATCH 16/24] xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly Christoph Hellwig
2018-06-15 13:02 ` [PATCH 17/24] xfs: remove the imap_valid flag Christoph Hellwig
2018-06-15 13:02 ` [PATCH 18/24] xfs: don't look at buffer heads in xfs_add_to_ioend Christoph Hellwig
2018-06-15 13:02 ` [PATCH 19/24] xfs: move all writeback buffer_head manipulation into xfs_map_at_offset Christoph Hellwig
2018-06-15 13:02 ` [PATCH 20/24] xfs: remove xfs_start_page_writeback Christoph Hellwig
2018-06-15 13:02 ` [PATCH 21/24] xfs: refactor the tail of xfs_writepage_map Christoph Hellwig
2018-06-15 13:02 ` [PATCH 22/24] xfs: allow writeback on pages without buffer heads Christoph Hellwig
2018-06-15 13:02 ` [PATCH 23/24] iomap: add support for sub-pagesize buffered I/O " Christoph Hellwig
2018-06-19 16:52 ` Brian Foster
2018-06-20 7:56 ` Christoph Hellwig [this message]
2018-06-20 14:32 ` Brian Foster
2018-06-20 16:08 ` Darrick J. Wong
2018-06-20 18:12 ` Brian Foster
2018-06-20 19:02 ` Darrick J. Wong
2018-06-21 8:46 ` Christoph Hellwig
2018-06-23 13:06 ` Brian Foster
2018-06-29 15:59 ` Christoph Hellwig
2018-07-02 12:50 ` Christoph Hellwig
2018-07-02 18:16 ` Brian Foster
2018-06-21 7:53 ` Christoph Hellwig
2018-06-15 13:02 ` [PATCH 24/24] xfs: add support for sub-pagesize writeback without buffer_heads Christoph Hellwig
2018-06-19 6:15 ` Darrick J. Wong
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