From: David Sterba <dsterba@suse.cz>
To: David Sterba <dsterba@suse.cz>
Cc: Josef Bacik <josef@toxicpanda.com>,
linux-btrfs@vger.kernel.org, kernel-team@fb.com,
stable@vger.kernel.org
Subject: Re: [PATCH] btrfs: save i_size in compress_file_range
Date: Mon, 4 Nov 2019 20:59:33 +0100 [thread overview]
Message-ID: <20191104195933.GG3001@twin.jikos.cz> (raw)
In-Reply-To: <20191023165102.GC3001@twin.jikos.cz>
On Wed, Oct 23, 2019 at 06:51:02PM +0200, David Sterba wrote:
> On Fri, Oct 11, 2019 at 09:03:54AM -0400, Josef Bacik wrote:
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -474,6 +474,7 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
> > u64 start = async_chunk->start;
> > u64 end = async_chunk->end;
> > u64 actual_end;
> > + loff_t i_size = i_size_read(inode);
> > int ret = 0;
> > struct page **pages = NULL;
> > unsigned long nr_pages;
> > @@ -488,7 +489,13 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
> > inode_should_defrag(BTRFS_I(inode), start, end, end - start + 1,
> > SZ_16K);
> >
> > - actual_end = min_t(u64, i_size_read(inode), end + 1);
> > + /*
> > + * We need to save i_size before now because it could change in between
> > + * us evaluating the size and assigning it. This is because we lock and
> > + * unlock the page in truncate and fallocate, and then modify the i_size
> > + * later on.
> > + */
> > + actual_end = min_t(u64, i_size, end + 1);
>
> Ping. This is not a future proof fix, please update the changelog and
> code according to the reply I sent.
The vfs i_size_read patch is being ignored so I guess we're on our own.
I have postponed last weeks pull request so I'll add this patch on top
and send in a day or two. The READ_ONCE will be simulated by barrier()s,
I've verified the assembly and actually that's alwo what read once does
among other things.
prev parent reply other threads:[~2019-11-04 19:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 13:03 [PATCH] btrfs: save i_size in compress_file_range Josef Bacik
2019-10-11 15:28 ` Filipe Manana
2019-10-11 17:15 ` Josef Bacik
2019-10-14 11:52 ` David Sterba
2019-10-23 16:51 ` David Sterba
2019-11-04 19:59 ` David Sterba [this message]
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