Squashfs: Refactor decompressor interface and code

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

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>

1 files changed, 49 insertions, 40 deletions

diff --git a/fs/squashfs/xz_wrapper.c b/fs/squashfs/xz_wrapper.c
index 1760b7d108f6..5d1d07cca6b4 100644
--- a/fs/squashfs/xz_wrapper.c
+++ b/fs/squashfs/xz_wrapper.c
@@ -38,38 +38,63 @@ struct squashfs_xz {
 	struct xz_buf buf;
 };
 
-struct comp_opts {
+struct disk_comp_opts {
 	__le32 dictionary_size;
 	__le32 flags;
 };
 
-static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff,
-	int len)
+struct comp_opts {
+	int dict_size;
+};
+
+static void *squashfs_xz_comp_opts(struct squashfs_sb_info *msblk,
+	void *buff, int len)
 {
-	struct comp_opts *comp_opts = buff;
-	struct squashfs_xz *stream;
-	int dict_size = msblk->block_size;
-	int err, n;
+	struct disk_comp_opts *comp_opts = buff;
+	struct comp_opts *opts;
+	int err = 0, n;
+
+	opts = kmalloc(sizeof(*opts), GFP_KERNEL);
+	if (opts == NULL) {
+		err = -ENOMEM;
+		goto out2;
+	}
 
 	if (comp_opts) {
 		/* check compressor options are the expected length */
 		if (len < sizeof(*comp_opts)) {
 			err = -EIO;
-			goto failed;
+			goto out;
 		}
 
-		dict_size = le32_to_cpu(comp_opts->dictionary_size);
+		opts->dict_size = le32_to_cpu(comp_opts->dictionary_size);
 
 		/* the dictionary size should be 2^n or 2^n+2^(n+1) */
-		n = ffs(dict_size) - 1;
-		if (dict_size != (1 << n) && dict_size != (1 << n) +
+		n = ffs(opts->dict_size) - 1;
+		if (opts->dict_size != (1 << n) && opts->dict_size != (1 << n) +
 						(1 << (n + 1))) {
 			err = -EIO;
-			goto failed;
+			goto out;
 		}
-	}
+	} else
+		/* use defaults */
+		opts->dict_size = max_t(int, msblk->block_size,
+							SQUASHFS_METADATA_SIZE);
 
-	dict_size = max_t(int, dict_size, SQUASHFS_METADATA_SIZE);
+	return opts;
+
+out:
+	kfree(opts);
+out2:
+	return ERR_PTR(err);
+}
+
+
+static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff)
+{
+	struct comp_opts *comp_opts = buff;
+	struct squashfs_xz *stream;
+	int err;
 
 	stream = kmalloc(sizeof(*stream), GFP_KERNEL);
 	if (stream == NULL) {
@@ -77,7 +102,7 @@ static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff,
 		goto failed;
 	}
 
-	stream->state = xz_dec_init(XZ_PREALLOC, dict_size);
+	stream->state = xz_dec_init(XZ_PREALLOC, comp_opts->dict_size);
 	if (stream->state == NULL) {
 		kfree(stream);
 		err = -ENOMEM;
@@ -103,15 +128,13 @@ static void squashfs_xz_free(void *strm)
 }
 
 
-static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void **buffer,
-	struct buffer_head **bh, int b, int offset, int length, int srclength,
-	int pages)
+static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
+	void **buffer, struct buffer_head **bh, int b, int offset, int length,
+	int srclength, int pages)
 {
 	enum xz_ret xz_err;
 	int avail, total = 0, k = 0, page = 0;
-	struct squashfs_xz *stream = msblk->stream;
-
-	mutex_lock(&msblk->read_data_mutex);
+	struct squashfs_xz *stream = strm;
 
 	xz_dec_reset(stream->state);
 	stream->buf.in_pos = 0;
@@ -124,10 +147,6 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void **buffer,
 		if (stream->buf.in_pos == stream->buf.in_size && k < b) {
 			avail = min(length, msblk->devblksize - offset);
 			length -= avail;
-			wait_on_buffer(bh[k]);
-			if (!buffer_uptodate(bh[k]))
-				goto release_mutex;
-
 			stream->buf.in = bh[k]->b_data + offset;
 			stream->buf.in_size = avail;
 			stream->buf.in_pos = 0;
@@ -147,23 +166,12 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void **buffer,
 			put_bh(bh[k++]);
 	} while (xz_err == XZ_OK);
 
-	if (xz_err != XZ_STREAM_END) {
-		ERROR("xz_dec_run error, data probably corrupt\n");
-		goto release_mutex;
-	}
-
-	if (k < b) {
-		ERROR("xz_uncompress error, input remaining\n");
-		goto release_mutex;
-	}
-
-	total += stream->buf.out_pos;
-	mutex_unlock(&msblk->read_data_mutex);
-	return total;
+	if (xz_err != XZ_STREAM_END || k < b)
+		goto out;
 
-release_mutex:
-	mutex_unlock(&msblk->read_data_mutex);
+	return total + stream->buf.out_pos;
 
+out:
 	for (; k < b; k++)
 		put_bh(bh[k]);
 
@@ -172,6 +180,7 @@ release_mutex:
 
 const struct squashfs_decompressor squashfs_xz_comp_ops = {
 	.init = squashfs_xz_init,
+	.comp_opts = squashfs_xz_comp_opts,
 	.free = squashfs_xz_free,
 	.decompress = squashfs_xz_uncompress,
 	.id = XZ_COMPRESSION,