Hi Richard,
On 5/1/07, Richard Purdie <rpurdie@xxxxxxxxxxxxxx> wrote:
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 <rpurdie@xxxxxxxxxxxxxx>
---
[...]
+++ b/fs/jffs2/compr_lzo.c
[...]
+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;
+}
+
+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.
Thanks,
Satyam
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