linux-kernel - [PATCH 7/8] lib/zlib: DFLTCC support inflate with small window

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Message-Id: <20230126131428.1222214-8-zaslonko@linux.ibm.com>
Date:   Thu, 26 Jan 2023 14:14:27 +0100
From:   Mikhail Zaslonko <zaslonko@...ux.ibm.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Mikhail Zaslonko <zaslonko@...ux.ibm.com>
Subject: [PATCH 7/8] lib/zlib: DFLTCC support inflate with small window

There is no hardware control for DFLTCC window size.
After this change, software and hardware window formats no longer
match: the software will use wbits and wsize, and the hardware will use
HB_BITS and HB_SIZE.

Since neither dictionary manipulation nor internal allocation functions
are relevant to kernel zlib and zlib_inflate_workspacesize() always use
MAX_WBITS for window size calculation, only dfltcc_can_inflate() and
dfltcc_inflate() functions are affected by this patch.

This commit is based on:
  https://github.com/zlib-ng/zlib-ng/commit/3eab317

Signed-off-by: Mikhail Zaslonko <zaslonko@...ux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 lib/zlib_dfltcc/dfltcc_inflate.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/lib/zlib_dfltcc/dfltcc_inflate.c b/lib/zlib_dfltcc/dfltcc_inflate.c
index a16f416c8811..5786030c6dc2 100644
--- a/lib/zlib_dfltcc/dfltcc_inflate.c
+++ b/lib/zlib_dfltcc/dfltcc_inflate.c
@@ -22,10 +22,6 @@ int dfltcc_can_inflate(
             zlib_dfltcc_support == ZLIB_DFLTCC_DEFLATE_ONLY)
         return 0;
 
-    /* Unsupported compression settings */
-    if (state->wbits != HB_BITS)
-        return 0;
-
     /* Unsupported hardware */
     return is_bit_set(dfltcc_state->af.fns, DFLTCC_XPND) &&
                is_bit_set(dfltcc_state->af.fmts, DFLTCC_FMT0);
@@ -129,8 +125,6 @@ dfltcc_inflate_action dfltcc_inflate(
     /* Translate stream to parameter block */
     param->cvt = CVT_ADLER32;
     param->sbb = state->bits;
-    param->hl = state->whave; /* Software and hardware history formats match */
-    param->ho = (state->write - state->whave) & ((1 << HB_BITS) - 1);
     if (param->hl)
         param->nt = 0; /* Honor history for the first block */
     param->cv = state->check;
@@ -144,8 +138,6 @@ dfltcc_inflate_action dfltcc_inflate(
     strm->msg = oesc_msg(dfltcc_state->msg, param->oesc);
     state->last = cc == DFLTCC_CC_OK;
     state->bits = param->sbb;
-    state->whave = param->hl;
-    state->write = (param->ho + param->hl) & ((1 << HB_BITS) - 1);
     state->check = param->cv;
     if (cc == DFLTCC_CC_OP2_CORRUPT && param->oesc != 0) {
         /* Report an error if stream is corrupted */
-- 
2.34.1