From: Mike Marshall <hubcap@omnibond.com>
To: David Howells <dhowells@redhat.com>, Mike Marshall <hubcap@omnibond.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH v2] implement orangefs_readahead
Date: Sat, 24 Apr 2021 21:43:20 -0400 [thread overview]
Message-ID: <CAOg9mSTwNKPdRMwr_F87YCeUyxT775pBd5WcewGpcwSZFVz5=w@mail.gmail.com> (raw)
In-Reply-To: <1612829.1618587694@warthog.procyon.org.uk>
>> What happens if bytes_remaining < PAGE_SIZE?
I think on a call where that occurs, new_len won't get set
and readahead_expand won't get called. I don't see how that's
not correct, but I question me more than I question you :-) ...
>> what happens if bytes_remaining % PAGE_SIZE != 0
I think bytes_remaining % PAGE_SIZE worth of bytes won't get read on
that call, but that the readahead callout keeps getting called until all
the bytes are read? After you asked this, I thought about adding 1 to
new_len in such cases, and did some tests that way, it seems to me like it
works out as is.
>> I wonder if you should use iov_length(&iter)
iov_length has two arguments. The first one would maybe be iter.iov and
the second one would be... ?
>> should you cache inode->i_size lest it change under you due to truncate
That seems important, but I can't return an error from the void
readahead callout. Would I react by somehow returning the pages
back to their original condition, or ?
Anywho... I see that you've force pushed a new netfs... I think you
have it applied to a linus-tree-of-the-day on top of 5.12-rc4?
I have taken these patches from
git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git (netfs-lib)
0001-iov_iter-Add-ITER_XARRAY.patch
0002-mm-Add-set-end-wait-functions-for-PG_private_2.patch
0003-mm-filemap-Pass-the-file_ra_state-in-the-ractl.patch
0004-fs-Document-file_ra_state.patch
0005-mm-readahead-Handle-ractl-nr_pages-being-modified.patch
0006-mm-Implement-readahead_control-pageset-expansion.patch
0007-netfs-Make-a-netfs-helper-module.patch
0008-netfs-Documentation-for-helper-library.patch
0009-netfs-mm-Move-PG_fscache-helper-funcs-to-linux-netfs.patch
0010-netfs-mm-Add-set-end-wait_on_page_fscache-aliases.patch
0011-netfs-Provide-readahead-and-readpage-netfs-helpers.patch
0012-netfs-Add-tracepoints.patch
0013-netfs-Gather-stats.patch
0014-netfs-Add-write_begin-helper.patch
0015-netfs-Define-an-interface-to-talk-to-a-cache.patch
0016-netfs-Add-a-tracepoint-to-log-failures-that-would-be.patch
0017-fscache-cachefiles-Add-alternate-API-to-use-kiocb-fo.patch
... and added them on top of Linux 5.12-rc8 and added my
readahead patch to that.
Now I fail one extra xfstest, I fail generic/075, generic/112,
generic/127, generic/263 and generic/438. I haven't found an
obvious (to me) problem with my patch and I can't claim to understand
everything that is going on in the patches I have of yours...
I'll keep looking...
-Mike
On Fri, Apr 16, 2021 at 11:41 AM David Howells <dhowells@redhat.com> wrote:
>
> In orangefs_readahead():
>
> loff_t bytes_remaining = inode->i_size - readahead_pos(rac);
> loff_t pages_remaining = bytes_remaining / PAGE_SIZE;
>
> What happens if bytes_remaining < PAGE_SIZE? Or even what happens if
> bytes_remaining % PAGE_SIZE != 0?
>
> if ((ret = wait_for_direct_io(ORANGEFS_IO_READ, inode,
> &offset, &iter, readahead_length(rac),
> inode->i_size, NULL, NULL, file)) < 0)
>
> I wonder if you should use iov_length(&iter) rather than
> readahead_length(rac). They *should* be the same.
>
> Also, should you cache inode->i_size lest it change under you due to truncate?
>
> David
>
next prev parent reply other threads:[~2021-04-25 1:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-31 22:25 [RFC PATCH] implement orangefs_readahead Mike Marshall
2021-02-01 13:08 ` Matthew Wilcox
2021-02-02 3:32 ` Mike Marshall
2021-03-13 15:31 ` [RFC PATCH v2] " Mike Marshall
2021-03-17 3:04 ` Mike Marshall
2021-03-24 11:10 ` David Howells
2021-03-27 2:55 ` Mike Marshall
2021-03-27 3:50 ` Matthew Wilcox
2021-03-27 8:31 ` David Howells
2021-03-27 13:56 ` Matthew Wilcox
2021-03-27 15:40 ` Mike Marshall
2021-03-27 15:56 ` Matthew Wilcox
2021-03-28 3:04 ` Mike Marshall
2021-03-29 1:51 ` Mike Marshall
2021-03-29 9:37 ` David Howells
2021-03-29 23:25 ` Mike Marshall
[not found] ` <3726695.1617284551@warthog.procyon.org.uk >
2021-04-13 15:08 ` David Howells
2021-04-16 14:36 ` Mike Marshall
2021-04-16 15:14 ` Matthew Wilcox
2021-04-25 1:51 ` Mike Marshall
2021-04-16 15:41 ` David Howells
2021-04-25 1:43 ` Mike Marshall [this message]
2021-04-25 7:49 ` David Howells
2021-04-26 14:53 ` Mike Marshall
2021-04-26 19:01 ` Mike Marshall
2021-04-26 20:01 ` David Howells
2021-04-26 8:37 ` David Howells
2021-04-01 13:42 ` David Howells
2021-04-08 20:39 ` Mike Marshall
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