jffs2: Add LZO compression support to jffs2

Add LZO1X compression/decompression support to jffs2.

LZO's interface doesn't entirely match that required by jffs2 so a buffer and memcpy is unavoidable.

Signed-off-by Richard Purdie <[email protected]>

---

fs/Kconfig +0 -0

index a42f767..1645dfa 100644
@@ -1310,6 +1310,16 @@ config JFFS2_ZLIB
 
           Say 'Y' if unsure.

Add LZO1X compression/decompression support to jffs2.

LZO's interface doesn't entirely match that required by jffs2 so a buffer and memcpy is unavoidable.

Signed-off-by Richard Purdie <[email protected]>

---
[...]
+++ b/fs/jffs2/compr_lzo.c
[...]

fs/jffs2/compr_lzo.c new file +23 -0

+static void *lzo_mem;
+static void *lzo_compress_buf;
+static DEFINE_MUTEX(deflate_mutex);
+
+static void free_workspace(void)
+{
+       vfree(lzo_mem);
+       vfree(lzo_compress_buf);
+}
+
+static int __init alloc_workspace(void)
+{
+       lzo_mem = vmalloc(LZO1X_MEM_COMPRESS);
+       lzo_compress_buf = vmalloc(lzo1x_worst_compress(PAGE_SIZE));
+
+       if (!lzo_mem || !lzo_compress_buf) {
+               printk(KERN_WARNING "Failed to allocate lzo deflate workspace\n");
+               free_workspace();
+               return -ENOMEM;
+       }
+
+       return 0;
+}

Quoted 25 lines · Richard Purdie

+++ b/fs/jffs2/compr_lzo.c
[...]

fs/jffs2/compr_lzo.c new file +23 -0

+static void *lzo_mem;
+static void *lzo_compress_buf;
+static DEFINE_MUTEX(deflate_mutex);
+
+static void free_workspace(void)
+{
+       vfree(lzo_mem);
+       vfree(lzo_compress_buf);
+}
+
+static int __init alloc_workspace(void)
+{
+       lzo_mem = vmalloc(LZO1X_MEM_COMPRESS);
+       lzo_compress_buf = vmalloc(lzo1x_worst_compress(PAGE_SIZE));
+
+       if (!lzo_mem || !lzo_compress_buf) {
+               printk(KERN_WARNING "Failed to allocate lzo deflate workspace\n");
+               free_workspace();
+               return -ENOMEM;
+       }
+
+       return 0;
+}

fs/jffs2/compr_lzo.c line 54

Quoted 10 lines

fs/jffs2/compr_lzo.c new file +10 -0

+
+static int jffs2_lzo_compress(unsigned char *data_in, unsigned char *cpage_out,
+                             uint32_t *sourcelen, uint32_t *dstlen, void *model)
+{
+       unsigned long compress_size;
+       int ret;
+
+       mutex_lock(&deflate_mutex);
+       ret = lzo1x_1_compress(data_in, *sourcelen, lzo_compress_buf, &compress_size, lzo_mem);
+       mutex_unlock(&deflate_mutex);

Considering we do have to memcpy() the entire compressed result to the

destination output buffer later anyway (note that fs/jffs2/compr_zlib.c doesn't need to do that), do we really gain much by avoiding vmalloc() and vfree() in jffs2_lzo_compress() itself and keeping the workspace buffers pre-allocated? I ask because I always found these global static workspace buffers ugly, and all the associated code + mutex could go away if we make them local to jffs2_lzo_compress() -- as long as it doesn't hurt performance terribly, of course.