zlib: slim down zlib_deflate() workspace when possible

Instead of always creating a huge (268K) deflate_workspace with the
maximum compression parameters (windowBits=15, memLevel=8), allow the
caller to obtain a smaller workspace by specifying smaller parameter
values.

For example, when capturing oops and panic reports to a medium with
limited capacity, such as NVRAM, compression may be the only way to
capture the whole report.  In this case, a small workspace (24K works
fine) is a win, whether you allocate the workspace when you need it (i.e.,
during an oops or panic) or at boot time.

I've verified that this patch works with all accepted values of windowBits
(positive and negative), memLevel, and compression level.

Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/crypto/deflate.c b/crypto/deflate.c
index cbc7a33a9600..b5ccae29be74 100644
--- a/crypto/deflate.c
+++ b/crypto/deflate.c
@@ -48,7 +48,8 @@ static int deflate_comp_init(struct deflate_ctx *ctx)
         int ret = 0;
         struct z_stream_s *stream = &ctx->comp_stream;
 
-        stream->workspace = vzalloc(zlib_deflate_workspacesize());
+        stream->workspace = vzalloc(zlib_deflate_workspacesize(
+                                -DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL));
         if (!stream->workspace) {
                 ret = -ENOMEM;
                 goto out;