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Message-ID: <20131014021145.GH6847@bbox>
Date: Mon, 14 Oct 2013 11:11:45 +0900
From: Minchan Kim <minchan@...nel.org>
To: Phillip Lougher <phillip@...ashfs.org.uk>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Squashfs: Refactor decompressor interface and code
On Tue, Oct 08, 2013 at 03:14:10AM +0100, Phillip Lougher wrote:
> The decompressor interface and code was written from
> the point of view of single-threaded operation. In doing
> so it mixed a lot of single-threaded implementation specific
> aspects into the decompressor code and elsewhere which makes it
> difficult to seamlessly support multiple different decompressor
> implementations.
>
> This patch does the following:
>
> 1. It removes compressor_options parsing from the decompressor
> init() function. This allows the decompressor init() function
> to be dynamically called to instantiate multiple decompressors,
> without the compressor options needing to be read and parsed each
> time.
>
> 2. It moves threading and all sleeping operations out of the
> decompressors. In doing so, it makes the decompressors
> non-blocking wrappers which only deal with interfacing with
> the decompressor implementation.
>
> 3. It splits decompressor.[ch] into decompressor generic functions
> in decompressor.[ch], and moves the single threaded
> decompressor implementation into decompressor_single.c.
>
> The result of this patch is Squashfs should now be able to
> support multiple decompressors by adding new decompressor_xxx.c
> files with specialised implementations of the functions in
> decompressor_single.c
>
> This has the following functions
>
> decompressor_create()
> - Called at mount time to initialise internal decompressor state.
> - An opaque pointer to the decompressor private state is returned (or error).
> - The function is called with a pointer to the parsed and swapped comp_opts
> structure returned by the new decompressor comp_opts() call.
>
> decompressor_destroy()
> - Destroy all decompressor private state
> - kfree the comp_opts buffer
>
> decompress()
> - Select a decompressor or create a new decompressor
> - Call using whatever locking scheme is necessary
>
> All decompressor implementation specific private state has been moved from the
> squashfs_sb_info structure into the opaque private state returned by
> decompressor_create(). This is deliberate, now all implementation specific
> code has been moved to decompressor_xxx.c, no other code needs to/or should need
> to access anything within it.
>
> Signed-off-by: Phillip Lougher <phillip@...ashfs.org.uk>
> ---
> fs/squashfs/Makefile | 2 +-
> fs/squashfs/block.c | 11 ++--
> fs/squashfs/decompressor.c | 47 +++++++++++------
> fs/squashfs/decompressor.h | 21 +++-----
> fs/squashfs/decompressor_single.c | 107 ++++++++++++++++++++++++++++++++++++++
> fs/squashfs/lzo_wrapper.c | 24 ++-------
> fs/squashfs/squashfs.h | 9 +++-
> fs/squashfs/squashfs_fs_sb.h | 3 +-
> fs/squashfs/super.c | 10 ++--
> fs/squashfs/xz_wrapper.c | 89 +++++++++++++++++--------------
> fs/squashfs/zlib_wrapper.c | 50 ++++++------------
> 11 files changed, 237 insertions(+), 136 deletions(-)
> create mode 100644 fs/squashfs/decompressor_single.c
>
> diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
> index 110b047..c223c84 100644
> --- a/fs/squashfs/Makefile
> +++ b/fs/squashfs/Makefile
> @@ -4,7 +4,7 @@
>
> obj-$(CONFIG_SQUASHFS) += squashfs.o
> squashfs-y += block.o cache.o dir.o export.o file.o fragment.o id.o inode.o
> -squashfs-y += namei.o super.o symlink.o decompressor.o
> +squashfs-y += namei.o super.o symlink.o decompressor.o decompressor_single.o
> squashfs-$(CONFIG_SQUASHFS_XATTR) += xattr.o xattr_id.o
> squashfs-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o
> squashfs-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o
> diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
> index 41d108e..10993e9 100644
> --- a/fs/squashfs/block.c
> +++ b/fs/squashfs/block.c
> @@ -93,7 +93,7 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
> struct buffer_head **bh;
> int offset = index & ((1 << msblk->devblksize_log2) - 1);
> u64 cur_index = index >> msblk->devblksize_log2;
> - int bytes, compressed, b = 0, k = 0, page = 0, avail;
> + int bytes, compressed, b = 0, k = 0, page = 0, avail, i;
>
> bh = kcalloc(((srclength + msblk->devblksize - 1)
> >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
> @@ -158,6 +158,12 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
> ll_rw_block(READ, b - 1, bh + 1);
> }
>
> + for (i = 0; i < b; i++) {
> + wait_on_buffer(bh[i]);
> + if (!buffer_uptodate(bh[i]))
> + goto block_release;
> + }
Please, use tab instead of white space.
--
Kind regards,
Minchan Kim
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