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From: Josef Bacik <josef@toxicpanda.com>
To: Omar Sandoval <osandov@osandov.com>,
	linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>, Jann Horn <jannh@google.com>,
	Amir Goldstein <amir73il@gmail.com>,
	Aleksa Sarai <cyphar@cyphar.com>,
	linux-api@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v5 8/9] btrfs: implement RWF_ENCODED reads
Date: Mon, 24 Aug 2020 15:54:29 -0400	[thread overview]
Message-ID: <06545b90-976e-35a7-182d-8e005fc6b199@toxicpanda.com> (raw)
In-Reply-To: <a52f9e7743bb924cdfa87906295e422bc48801c7.1597993855.git.osandov@osandov.com>

On 8/21/20 3:38 AM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> There are 4 main cases:
> 
> 1. Inline extents: we copy the data straight out of the extent buffer.
> 2. Hole/preallocated extents: we fill in zeroes.
> 3. Regular, uncompressed extents: we read the sectors we need directly
>     from disk.
> 4. Regular, compressed extents: we read the entire compressed extent
>     from disk and indicate what subset of the decompressed extent is in
>     the file.
> 
> This initial implementation simplifies a few things that can be improved
> in the future:
> 
> - We hold the inode lock during the operation.
> - Cases 1, 3, and 4 allocate temporary memory to read into before
>    copying out to userspace.
> 
> Signed-off-by: Omar Sandoval <osandov@fb.com>


<snip>

> +	tmp = kmalloc(count, GFP_NOFS);
> +	if (!tmp) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +	read_extent_buffer(leaf, tmp, ptr, count);
> +	btrfs_free_path(path);

Why not just btrfs_release_path(), you're freeing below anyway.

Also a mention that we're explicitly not handling read repairs and backup copies 
would be good in the changelog as well.  Thanks,

Josef

  reply	other threads:[~2020-08-24 19:54 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21  7:38 [PATCH v5 0/9] fs: interface for directly reading/writing compressed data Omar Sandoval
2020-08-21  7:38 ` [PATCH man-pages v5] Document encoded I/O Omar Sandoval
2020-08-21  9:24   ` Amir Goldstein
2020-08-24 18:15     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 1/9] iov_iter: add copy_struct_from_iter() Omar Sandoval
2020-08-24 18:52   ` Josef Bacik
2020-08-24 21:09     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 2/9] fs: add O_ALLOW_ENCODED open flag Omar Sandoval
2020-08-24 18:28   ` Josef Bacik
2020-08-24 21:11     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 3/9] fs: add RWF_ENCODED for reading/writing compressed data Omar Sandoval
2020-08-21  8:47   ` Amir Goldstein
2020-08-24 23:49     ` Omar Sandoval
2020-08-25  8:25       ` Amir Goldstein
2020-08-25 17:20         ` Omar Sandoval
2020-08-24 19:07   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 4/9] btrfs: don't advance offset for compressed bios in btrfs_csum_one_bio() Omar Sandoval
2020-08-24 19:17   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 5/9] btrfs: add ram_bytes and offset to btrfs_ordered_extent Omar Sandoval
2020-08-24 19:23   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 6/9] btrfs: support different disk extent size for delalloc Omar Sandoval
2020-08-24 19:26   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 7/9] btrfs: optionally extend i_size in cow_file_range_inline() Omar Sandoval
2020-08-24 19:33   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 8/9] btrfs: implement RWF_ENCODED reads Omar Sandoval
2020-08-24 19:54   ` Josef Bacik [this message]
2020-08-24 21:23     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 9/9] btrfs: implement RWF_ENCODED writes Omar Sandoval
2020-08-24 20:30   ` Josef Bacik
2020-08-24 21:30     ` Omar Sandoval

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