Squashfs: Generalise paging handling in the decompressors

Further generalise the decompressors by adding a page handler
abstraction.  This adds helpers to allow the decompressors
to access and process the output buffers in an implementation
independant manner.

This allows different types of output buffer to be passed
to the decompressors, with the implementation specific
aspects handled at decompression time, but without the
knowledge being held in the decompressor wrapper code.

This will allow the decompressors to handle Squashfs
cache buffers, and page cache pages.

This patch adds the abstraction and an implementation for
the caches.

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

13 files changed, 163 insertions, 67 deletions

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 4dd402597f22..0cea9b9236d0 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -36,6 +36,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 /*
  * Read the metadata block length, this is stored in the first two
@@ -86,16 +87,16 @@ static struct buffer_head *get_block_length(struct super_block *sb,
  * generated a larger block - this does occasionally happen with compression
  * algorithms).
  */
-int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
-                        int length, u64 *next_index, int srclength, int pages)
+int squashfs_read_data(struct super_block *sb, u64 index, int length,
+                u64 *next_index, struct squashfs_page_actor *output)
 {
         struct squashfs_sb_info *msblk = sb->s_fs_info;
         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, i;
+        int bytes, compressed, b = 0, k = 0, avail, i;
 
-        bh = kcalloc(((srclength + msblk->devblksize - 1)
+        bh = kcalloc(((output->length + msblk->devblksize - 1)
                 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
         if (bh == NULL)
                 return -ENOMEM;
@@ -111,9 +112,9 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
                         *next_index = index + length;
 
                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
-                        index, compressed ? "" : "un", length, srclength);
+                        index, compressed ? "" : "un", length, output->length);
 
-                if (length < 0 || length > srclength ||
+                if (length < 0 || length > output->length ||
                                 (index + length) > msblk->bytes_used)
                         goto read_failure;
 
@@ -145,7 +146,7 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
                                 compressed ? "" : "un", length);
 
-                if (length < 0 || length > srclength ||
+                if (length < 0 || length > output->length ||
                                         (index + length) > msblk->bytes_used)
                         goto block_release;
 
@@ -165,8 +166,8 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
         }
 
         if (compressed) {
-                length = squashfs_decompress(msblk, buffer, bh, b, offset,
-                         length, srclength, pages);
+                length = squashfs_decompress(msblk, bh, b, offset, length,
+                        output);
                 if (length < 0)
                         goto read_failure;
         } else {
@@ -174,19 +175,20 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
                  * Block is uncompressed.
                  */
                 int in, pg_offset = 0;
+                void *data = squashfs_first_page(output);
 
                 for (bytes = length; k < b; k++) {
                         in = min(bytes, msblk->devblksize - offset);
                         bytes -= in;
                         while (in) {
                                 if (pg_offset == PAGE_CACHE_SIZE) {
-                                        page++;
+                                        data = squashfs_next_page(output);
                                         pg_offset = 0;
                                 }
                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
                                                 pg_offset);
-                                memcpy(buffer[page] + pg_offset,
-                                                bh[k]->b_data + offset, avail);
+                                memcpy(data + pg_offset, bh[k]->b_data + offset,
+                                                avail);
                                 in -= avail;
                                 pg_offset += avail;
                                 offset += avail;
@@ -194,6 +196,7 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
                         offset = 0;
                         put_bh(bh[k]);
                 }
+                squashfs_finish_page(output);
         }
 
         kfree(bh);
diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index af0b73802592..1cb70a0b2168 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -56,6 +56,7 @@
 #include "squashfs_fs.h"
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
+#include "page_actor.h"
 
 /*
  * Look-up block in cache, and increment usage count.  If not in cache, read
@@ -119,9 +120,8 @@ struct squashfs_cache_entry *squashfs_cache_get(struct super_block *sb,
                         entry->error = 0;
                         spin_unlock(&cache->lock);
 
-                        entry->length = squashfs_read_data(sb, entry->data,
-                                block, length, &entry->next_index,
-                                cache->block_size, cache->pages);
+                        entry->length = squashfs_read_data(sb, block, length,
+                                &entry->next_index, entry->actor);
 
                         spin_lock(&cache->lock);
 
@@ -220,6 +220,7 @@ void squashfs_cache_delete(struct squashfs_cache *cache)
                                 kfree(cache->entry[i].data[j]);
                         kfree(cache->entry[i].data);
                 }
+                kfree(cache->entry[i].actor);
         }
 
         kfree(cache->entry);
@@ -280,6 +281,13 @@ struct squashfs_cache *squashfs_cache_init(char *name, int entries,
                                 goto cleanup;
                         }
                 }
+
+                entry->actor = squashfs_page_actor_init(entry->data,
+                                                cache->pages, 0);
+                if (entry->actor == NULL) {
+                        ERROR("Failed to allocate %s cache entry\n", name);
+                        goto cleanup;
+                }
         }
 
         return cache;
@@ -410,6 +418,7 @@ void *squashfs_read_table(struct super_block *sb, u64 block, int length)
         int pages = (length + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
         int i, res;
         void *table, *buffer, **data;
+        struct squashfs_page_actor *actor;
 
         table = buffer = kmalloc(length, GFP_KERNEL);
         if (table == NULL)
@@ -421,19 +430,28 @@ void *squashfs_read_table(struct super_block *sb, u64 block, int length)
                 goto failed;
         }
 
+        actor = squashfs_page_actor_init(data, pages, length);
+        if (actor == NULL) {
+                res = -ENOMEM;
+                goto failed2;
+        }
+
         for (i = 0; i < pages; i++, buffer += PAGE_CACHE_SIZE)
                 data[i] = buffer;
 
-        res = squashfs_read_data(sb, data, block, length |
-                SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, length, pages);
+        res = squashfs_read_data(sb, block, length |
+                SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, actor);
 
         kfree(data);
+        kfree(actor);
 
         if (res < 0)
                 goto failed;
 
         return table;
 
+failed2:
+        kfree(data);
 failed:
         kfree(table);
         return ERR_PTR(res);
diff --git a/fs/squashfs/decompressor.c b/fs/squashfs/decompressor.c
index 234291f79ba5..ac22fe73b0ad 100644
--- a/fs/squashfs/decompressor.c
+++ b/fs/squashfs/decompressor.c
@@ -30,6 +30,7 @@
 #include "squashfs_fs_sb.h"
 #include "decompressor.h"
 #include "squashfs.h"
+#include "page_actor.h"
 
 /*
  * This file (and decompressor.h) implements a decompressor framework for
@@ -87,6 +88,7 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
 {
         struct squashfs_sb_info *msblk = sb->s_fs_info;
         void *buffer = NULL, *comp_opts;
+        struct squashfs_page_actor *actor = NULL;
         int length = 0;
 
         /*
@@ -99,9 +101,14 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
                         goto out;
                 }
 
-                length = squashfs_read_data(sb, &buffer,
-                        sizeof(struct squashfs_super_block), 0, NULL,
-                                PAGE_CACHE_SIZE, 1);
+                actor = squashfs_page_actor_init(&buffer, 1, 0);
+                if (actor == NULL) {
+                        comp_opts = ERR_PTR(-ENOMEM);
+                        goto out;
+                }
+
+                length = squashfs_read_data(sb,
+                        sizeof(struct squashfs_super_block), 0, NULL, actor);
 
                 if (length < 0) {
                         comp_opts = ERR_PTR(length);
@@ -112,6 +119,7 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
         comp_opts = squashfs_comp_opts(msblk, buffer, length);
 
 out:
+        kfree(actor);
         kfree(buffer);
         return comp_opts;
 }
diff --git a/fs/squashfs/decompressor.h b/fs/squashfs/decompressor.h
index 6cdb20a3878a..af0985321808 100644
--- a/fs/squashfs/decompressor.h
+++ b/fs/squashfs/decompressor.h
@@ -27,8 +27,9 @@ struct squashfs_decompressor {
         void    *(*init)(struct squashfs_sb_info *, void *);
         void    *(*comp_opts)(struct squashfs_sb_info *, void *, int);
         void    (*free)(void *);
-        int     (*decompress)(struct squashfs_sb_info *, void *, void **,
-                struct buffer_head **, int, int, int, int, int);
+        int     (*decompress)(struct squashfs_sb_info *, void *,
+                struct buffer_head **, int, int, int,
+                struct squashfs_page_actor *);
         int     id;
         char    *name;
         int     supported;
diff --git a/fs/squashfs/decompressor_multi.c b/fs/squashfs/decompressor_multi.c
index 462731db5130..ae54675a3526 100644
--- a/fs/squashfs/decompressor_multi.c
+++ b/fs/squashfs/decompressor_multi.c
@@ -183,15 +183,14 @@ wait:
 }
 
 
-int squashfs_decompress(struct squashfs_sb_info *msblk,
-        void **buffer, struct buffer_head **bh, int b, int offset, int length,
-        int srclength, int pages)
+int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
+        int b, int offset, int length, struct squashfs_page_actor *output)
 {
         int res;
         struct squashfs_stream *stream = msblk->stream;
         struct decomp_stream *decomp_stream = get_decomp_stream(msblk, stream);
         res = msblk->decompressor->decompress(msblk, decomp_stream->stream,
-                buffer, bh, b, offset, length, srclength, pages);
+                bh, b, offset, length, output);
         put_decomp_stream(decomp_stream, stream);
         if (res < 0)
                 ERROR("%s decompression failed, data probably corrupt\n",
diff --git a/fs/squashfs/decompressor_multi_percpu.c b/fs/squashfs/decompressor_multi_percpu.c
index 0e7b679bc4ad..23a9c28ad8ea 100644
--- a/fs/squashfs/decompressor_multi_percpu.c
+++ b/fs/squashfs/decompressor_multi_percpu.c
@@ -74,15 +74,14 @@ void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
         }
 }
 
-int squashfs_decompress(struct squashfs_sb_info *msblk,
-        void **buffer, struct buffer_head **bh, int b, int offset, int length,
-        int srclength, int pages)
+int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
+        int b, int offset, int length, struct squashfs_page_actor *output)
 {
         struct squashfs_stream __percpu *percpu =
                         (struct squashfs_stream __percpu *) msblk->stream;
         struct squashfs_stream *stream = get_cpu_ptr(percpu);
-        int res = msblk->decompressor->decompress(msblk, stream->stream, buffer,
-                bh, b, offset, length, srclength, pages);
+        int res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
+                offset, length, output);
         put_cpu_ptr(stream);
 
         if (res < 0)
diff --git a/fs/squashfs/decompressor_single.c b/fs/squashfs/decompressor_single.c
index f857cf6f22d4..a6c75929a00e 100644
--- a/fs/squashfs/decompressor_single.c
+++ b/fs/squashfs/decompressor_single.c
@@ -61,16 +61,15 @@ void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
         }
 }
 
-int squashfs_decompress(struct squashfs_sb_info *msblk,
-        void **buffer, struct buffer_head **bh, int b, int offset, int length,
-        int srclength, int pages)
+int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
+        int b, int offset, int length, struct squashfs_page_actor *output)
 {
         int res;
         struct squashfs_stream *stream = msblk->stream;
 
         mutex_lock(&stream->mutex);
-        res = msblk->decompressor->decompress(msblk, stream->stream, buffer,
-                bh, b, offset, length, srclength, pages);
+        res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
+                offset, length, output);
         mutex_unlock(&stream->mutex);
 
         if (res < 0)
diff --git a/fs/squashfs/lzo_wrapper.c b/fs/squashfs/lzo_wrapper.c
index 75c3b5779172..244b9fbfff7b 100644
--- a/fs/squashfs/lzo_wrapper.c
+++ b/fs/squashfs/lzo_wrapper.c
@@ -31,6 +31,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 struct squashfs_lzo {
         void    *input;
@@ -75,13 +76,13 @@ static void lzo_free(void *strm)
 
 
 static int lzo_uncompress(struct squashfs_sb_info *msblk, void *strm,
-        void **buffer, struct buffer_head **bh, int b, int offset, int length,
-        int srclength, int pages)
+        struct buffer_head **bh, int b, int offset, int length,
+        struct squashfs_page_actor *output)
 {
         struct squashfs_lzo *stream = strm;
-        void *buff = stream->input;
+        void *buff = stream->input, *data;
         int avail, i, bytes = length, res;
-        size_t out_len = srclength;
+        size_t out_len = output->length;
 
         for (i = 0; i < b; i++) {
                 avail = min(bytes, msblk->devblksize - offset);
@@ -98,12 +99,20 @@ static int lzo_uncompress(struct squashfs_sb_info *msblk, void *strm,
                 goto failed;
 
         res = bytes = (int)out_len;
-        for (i = 0, buff = stream->output; bytes && i < pages; i++) {
-                avail = min_t(int, bytes, PAGE_CACHE_SIZE);
-                memcpy(buffer[i], buff, avail);
-                buff += avail;
-                bytes -= avail;
+        data = squashfs_first_page(output);
+        buff = stream->output;
+        while (data) {
+                if (bytes <= PAGE_CACHE_SIZE) {
+                        memcpy(data, buff, bytes);
+                        break;
+                } else {
+                        memcpy(data, buff, PAGE_CACHE_SIZE);
+                        buff += PAGE_CACHE_SIZE;
+                        bytes -= PAGE_CACHE_SIZE;
+                        data = squashfs_next_page(output);
+                }
         }
+        squashfs_finish_page(output);
 
         return res;
 
diff --git a/fs/squashfs/page_actor.h b/fs/squashfs/page_actor.h
new file mode 100644
index 000000000000..5b0ba5a7133a
--- /dev/null
+++ b/fs/squashfs/page_actor.h
@@ -0,0 +1,49 @@
+#ifndef PAGE_ACTOR_H
+#define PAGE_ACTOR_H
+/*
+ * Copyright (c) 2013
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+struct squashfs_page_actor {
+        void    **page;
+        int     pages;
+        int     length;
+        int     next_page;
+};
+
+static inline struct squashfs_page_actor *squashfs_page_actor_init(void **page,
+        int pages, int length)
+{
+        struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
+
+        if (actor == NULL)
+                return NULL;
+
+        actor->length = length ? : pages * PAGE_CACHE_SIZE;
+        actor->page = page;
+        actor->pages = pages;
+        actor->next_page = 0;
+        return actor;
+}
+
+static inline void *squashfs_first_page(struct squashfs_page_actor *actor)
+{
+        actor->next_page = 1;
+        return actor->page[0];
+}
+
+static inline void *squashfs_next_page(struct squashfs_page_actor *actor)
+{
+        return actor->next_page == actor->pages ? NULL :
+                actor->page[actor->next_page++];
+}
+
+static inline void squashfs_finish_page(struct squashfs_page_actor *actor)
+{
+        /* empty */
+}
+#endif
diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 2e2751df8452..6a97e63ca173 100644
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -28,8 +28,8 @@
 #define WARNING(s, args...)     pr_warning("SQUASHFS: "s, ## args)
 
 /* block.c */
-extern int squashfs_read_data(struct super_block *, void **, u64, int, u64 *,
-                                int, int);
+extern int squashfs_read_data(struct super_block *, u64, int, u64 *,
+                                struct squashfs_page_actor *);
 
 /* cache.c */
 extern struct squashfs_cache *squashfs_cache_init(char *, int, int);
@@ -53,8 +53,8 @@ extern void *squashfs_decompressor_setup(struct super_block *, unsigned short);
 /* decompressor_xxx.c */
 extern void *squashfs_decompressor_create(struct squashfs_sb_info *, void *);
 extern void squashfs_decompressor_destroy(struct squashfs_sb_info *);
-extern int squashfs_decompress(struct squashfs_sb_info *, void **,
-        struct buffer_head **, int, int, int, int, int);
+extern int squashfs_decompress(struct squashfs_sb_info *, struct buffer_head **,
+        int, int, int, struct squashfs_page_actor *);
 extern int squashfs_max_decompressors(void);
 
 /* export.c */
diff --git a/fs/squashfs/squashfs_fs_sb.h b/fs/squashfs/squashfs_fs_sb.h
index 9cdcf4150d59..1da565cb50c3 100644
--- a/fs/squashfs/squashfs_fs_sb.h
+++ b/fs/squashfs/squashfs_fs_sb.h
@@ -50,6 +50,7 @@ struct squashfs_cache_entry {
         wait_queue_head_t       wait_queue;
         struct squashfs_cache   *cache;
         void                    **data;
+        struct squashfs_page_actor      *actor;
 };
 
 struct squashfs_sb_info {
diff --git a/fs/squashfs/xz_wrapper.c b/fs/squashfs/xz_wrapper.c
index 5d1d07cca6b4..c609624e4b8a 100644
--- a/fs/squashfs/xz_wrapper.c
+++ b/fs/squashfs/xz_wrapper.c
@@ -32,6 +32,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 struct squashfs_xz {
         struct xz_dec *state;
@@ -129,11 +130,11 @@ static void squashfs_xz_free(void *strm)
 
 
 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)
+        struct buffer_head **bh, int b, int offset, int length,
+        struct squashfs_page_actor *output)
 {
         enum xz_ret xz_err;
-        int avail, total = 0, k = 0, page = 0;
+        int avail, total = 0, k = 0;
         struct squashfs_xz *stream = strm;
 
         xz_dec_reset(stream->state);
@@ -141,7 +142,7 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
         stream->buf.in_size = 0;
         stream->buf.out_pos = 0;
         stream->buf.out_size = PAGE_CACHE_SIZE;
-        stream->buf.out = buffer[page++];
+        stream->buf.out = squashfs_first_page(output);
 
         do {
                 if (stream->buf.in_pos == stream->buf.in_size && k < b) {
@@ -153,11 +154,12 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
                         offset = 0;
                 }
 
-                if (stream->buf.out_pos == stream->buf.out_size
-                                                        && page < pages) {
-                        stream->buf.out = buffer[page++];
-                        stream->buf.out_pos = 0;
-                        total += PAGE_CACHE_SIZE;
+                if (stream->buf.out_pos == stream->buf.out_size) {
+                        stream->buf.out = squashfs_next_page(output);
+                        if (stream->buf.out != NULL) {
+                                stream->buf.out_pos = 0;
+                                total += PAGE_CACHE_SIZE;
+                        }
                 }
 
                 xz_err = xz_dec_run(stream->state, &stream->buf);
@@ -166,6 +168,8 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
                         put_bh(bh[k++]);
         } while (xz_err == XZ_OK);
 
+        squashfs_finish_page(output);
+
         if (xz_err != XZ_STREAM_END || k < b)
                 goto out;
 
diff --git a/fs/squashfs/zlib_wrapper.c b/fs/squashfs/zlib_wrapper.c
index bb049027d15c..8727caba6882 100644
--- a/fs/squashfs/zlib_wrapper.c
+++ b/fs/squashfs/zlib_wrapper.c
@@ -32,6 +32,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 static void *zlib_init(struct squashfs_sb_info *dummy, void *buff)
 {
@@ -62,14 +63,14 @@ static void zlib_free(void *strm)
 
 
 static int zlib_uncompress(struct squashfs_sb_info *msblk, void *strm,
-        void **buffer, struct buffer_head **bh, int b, int offset, int length,
-        int srclength, int pages)
+        struct buffer_head **bh, int b, int offset, int length,
+        struct squashfs_page_actor *output)
 {
-        int zlib_err, zlib_init = 0;
-        int k = 0, page = 0;
+        int zlib_err, zlib_init = 0, k = 0;
         z_stream *stream = strm;
 
-        stream->avail_out = 0;
+        stream->avail_out = PAGE_CACHE_SIZE;
+        stream->next_out = squashfs_first_page(output);
         stream->avail_in = 0;
 
         do {
@@ -81,15 +82,18 @@ static int zlib_uncompress(struct squashfs_sb_info *msblk, void *strm,
                         offset = 0;
                 }
 
-                if (stream->avail_out == 0 && page < pages) {
-                        stream->next_out = buffer[page++];
-                        stream->avail_out = PAGE_CACHE_SIZE;
+                if (stream->avail_out == 0) {
+                        stream->next_out = squashfs_next_page(output);
+                        if (stream->next_out != NULL)
+                                stream->avail_out = PAGE_CACHE_SIZE;
                 }
 
                 if (!zlib_init) {
                         zlib_err = zlib_inflateInit(stream);
-                        if (zlib_err != Z_OK)
+                        if (zlib_err != Z_OK) {
+                                squashfs_finish_page(output);
                                 goto out;
+                        }
                         zlib_init = 1;
                 }
 
@@ -99,6 +103,8 @@ static int zlib_uncompress(struct squashfs_sb_info *msblk, void *strm,
                         put_bh(bh[k++]);
         } while (zlib_err == Z_OK);
 
+        squashfs_finish_page(output);
+
         if (zlib_err != Z_STREAM_END)
                 goto out;