update ZFS submodule to debian/0.7.9-2

[zfsonlinux.git] / zfs-patches / 0025-Fix-zdb-R-decompression.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Chunwei Chen <david.chen@nutanix.com>
Date: Thu, 1 Feb 2018 16:19:36 -0800
Subject: [PATCH] Fix zdb -R decompression
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There are some issues in the zdb -R decompression implementation.

The first is that ZLE can easily decompress non-ZLE streams. So we add
ZDB_NO_ZLE env to make zdb skip ZLE.

The second is the random bytes appended to pabd, pbuf2 stuff. This serve
no purpose at all, those bytes shouldn't be read during decompression
anyway. Instead, we randomize lbuf2, so that we can make sure
decompression fill exactly to lsize by bcmp lbuf and lbuf2.

The last one is the condition to detect fail is wrong.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Closes #7099
Closes #4984
(cherry picked from commit 18c662b84566cd34e6f6fb982d6a01a415a4e3cd)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 cmd/zdb/zdb.c  | 38 ++++++++++++++++++--------------------
 man/man8/zdb.8 |  4 +++-
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index 0cc1656a8..2d80589ca 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -3895,13 +3895,6 @@ name:
 	return (NULL);
 }
 
-/* ARGSUSED */
-static int
-random_get_pseudo_bytes_cb(void *buf, size_t len, void *unused)
-{
-	return (random_get_pseudo_bytes(buf, len));
-}
-
 /*
  * Read a block from a pool and print it out.  The syntax of the
  * block descriptor is:
@@ -4064,17 +4057,8 @@ zdb_read_block(char *thing, spa_t *spa)
 		 * every decompress function at every inflated blocksize.
 		 */
 		enum zio_compress c;
-		void *pbuf2 = umem_alloc(SPA_MAXBLOCKSIZE, UMEM_NOFAIL);
 		void *lbuf2 = umem_alloc(SPA_MAXBLOCKSIZE, UMEM_NOFAIL);
 
-		abd_copy_to_buf(pbuf2, pabd, psize);
-
-		VERIFY0(abd_iterate_func(pabd, psize, SPA_MAXBLOCKSIZE - psize,
-		    random_get_pseudo_bytes_cb, NULL));
-
-		VERIFY0(random_get_pseudo_bytes((uint8_t *)pbuf2 + psize,
-		    SPA_MAXBLOCKSIZE - psize));
-
 		/*
 		 * XXX - On the one hand, with SPA_MAXBLOCKSIZE at 16MB,
 		 * this could take a while and we should let the user know
@@ -4084,13 +4068,29 @@ zdb_read_block(char *thing, spa_t *spa)
 		for (lsize = psize + SPA_MINBLOCKSIZE;
 		    lsize <= SPA_MAXBLOCKSIZE; lsize += SPA_MINBLOCKSIZE) {
 			for (c = 0; c < ZIO_COMPRESS_FUNCTIONS; c++) {
+				/*
+				 * ZLE can easily decompress non zle stream.
+				 * So have an option to disable it.
+				 */
+				if (c == ZIO_COMPRESS_ZLE &&
+				    getenv("ZDB_NO_ZLE"))
+					continue;
+
 				(void) fprintf(stderr,
 				    "Trying %05llx -> %05llx (%s)\n",
 				    (u_longlong_t)psize, (u_longlong_t)lsize,
 				    zio_compress_table[c].ci_name);
+
+				/*
+				 * We randomize lbuf2, and decompress to both
+				 * lbuf and lbuf2. This way, we will know if
+				 * decompression fill exactly to lsize.
+				 */
+				VERIFY0(random_get_pseudo_bytes(lbuf2, lsize));
+
 				if (zio_decompress_data(c, pabd,
 				    lbuf, psize, lsize) == 0 &&
-				    zio_decompress_data_buf(c, pbuf2,
+				    zio_decompress_data(c, pabd,
 				    lbuf2, psize, lsize) == 0 &&
 				    bcmp(lbuf, lbuf2, lsize) == 0)
 					break;
@@ -4098,11 +4098,9 @@ zdb_read_block(char *thing, spa_t *spa)
 			if (c != ZIO_COMPRESS_FUNCTIONS)
 				break;
 		}
-
-		umem_free(pbuf2, SPA_MAXBLOCKSIZE);
 		umem_free(lbuf2, SPA_MAXBLOCKSIZE);
 
-		if (lsize <= psize) {
+		if (lsize > SPA_MAXBLOCKSIZE) {
 			(void) printf("Decompress of %s failed\n", thing);
 			goto out;
 		}
diff --git a/man/man8/zdb.8 b/man/man8/zdb.8
index 4e47de7be..d991aae4c 100644
--- a/man/man8/zdb.8
+++ b/man/man8/zdb.8
@@ -246,7 +246,9 @@ and, optionally,
 .It Sy b Ar offset
 Print block pointer
 .It Sy d
-Decompress the block
+Decompress the block. Set environment variable
+.Nm ZBD_NO_ZLE
+to skip zle when guessing.
 .It Sy e
 Byte swap the block
 .It Sy g
-- 
2.14.2