zfs-patches/0025-Fix-zdb-R-decompression.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Chunwei Chen <david.chen@nutanix.com>
   3 Date: Thu, 1 Feb 2018 16:19:36 -0800
   4 Subject: [PATCH] Fix zdb -R decompression
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   7 Content-Transfer-Encoding: 8bit
   8
   9 There are some issues in the zdb -R decompression implementation.
  10
  11 The first is that ZLE can easily decompress non-ZLE streams. So we add
  12 ZDB_NO_ZLE env to make zdb skip ZLE.
  13
  14 The second is the random bytes appended to pabd, pbuf2 stuff. This serve
  15 no purpose at all, those bytes shouldn't be read during decompression
  16 anyway. Instead, we randomize lbuf2, so that we can make sure
  17 decompression fill exactly to lsize by bcmp lbuf and lbuf2.
  18
  19 The last one is the condition to detect fail is wrong.
  20
  21 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
  22 Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
  23 Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
  24 Closes #7099
  25 Closes #4984
  26 (cherry picked from commit 18c662b84566cd34e6f6fb982d6a01a415a4e3cd)
  27 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  28 ---
  29  cmd/zdb/zdb.c  | 38 ++++++++++++++++++--------------------
  30  man/man8/zdb.8 |  4 +++-
  31  2 files changed, 21 insertions(+), 21 deletions(-)
  32
  33 diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
  34 index 0cc1656a8..2d80589ca 100644
  35 --- a/cmd/zdb/zdb.c
  36 +++ b/cmd/zdb/zdb.c
  37 @@ -3895,13 +3895,6 @@ name:
  38         return (NULL);
  39  }
  40
  41 -/* ARGSUSED */
  42 -static int
  43 -random_get_pseudo_bytes_cb(void *buf, size_t len, void *unused)
  44 -{
  45 -       return (random_get_pseudo_bytes(buf, len));
  46 -}
  47 -
  48  /*
  49   * Read a block from a pool and print it out.  The syntax of the
  50   * block descriptor is:
  51 @@ -4064,17 +4057,8 @@ zdb_read_block(char *thing, spa_t *spa)
  52                  * every decompress function at every inflated blocksize.
  53                  */
  54                 enum zio_compress c;
  55 -               void *pbuf2 = umem_alloc(SPA_MAXBLOCKSIZE, UMEM_NOFAIL);
  56                 void *lbuf2 = umem_alloc(SPA_MAXBLOCKSIZE, UMEM_NOFAIL);
  57
  58 -               abd_copy_to_buf(pbuf2, pabd, psize);
  59 -
  60 -               VERIFY0(abd_iterate_func(pabd, psize, SPA_MAXBLOCKSIZE - psize,
  61 -                   random_get_pseudo_bytes_cb, NULL));
  62 -
  63 -               VERIFY0(random_get_pseudo_bytes((uint8_t *)pbuf2 + psize,
  64 -                   SPA_MAXBLOCKSIZE - psize));
  65 -
  66                 /*
  67                  * XXX - On the one hand, with SPA_MAXBLOCKSIZE at 16MB,
  68                  * this could take a while and we should let the user know
  69 @@ -4084,13 +4068,29 @@ zdb_read_block(char *thing, spa_t *spa)
  70                 for (lsize = psize + SPA_MINBLOCKSIZE;
  71                     lsize <= SPA_MAXBLOCKSIZE; lsize += SPA_MINBLOCKSIZE) {
  72                         for (c = 0; c < ZIO_COMPRESS_FUNCTIONS; c++) {
  73 +                               /*
  74 +                                * ZLE can easily decompress non zle stream.
  75 +                                * So have an option to disable it.
  76 +                                */
  77 +                               if (c == ZIO_COMPRESS_ZLE &&
  78 +                                   getenv("ZDB_NO_ZLE"))
  79 +                                       continue;
  80 +
  81                                 (void) fprintf(stderr,
  82                                     "Trying %05llx -> %05llx (%s)\n",
  83                                     (u_longlong_t)psize, (u_longlong_t)lsize,
  84                                     zio_compress_table[c].ci_name);
  85 +
  86 +                               /*
  87 +                                * We randomize lbuf2, and decompress to both
  88 +                                * lbuf and lbuf2. This way, we will know if
  89 +                                * decompression fill exactly to lsize.
  90 +                                */
  91 +                               VERIFY0(random_get_pseudo_bytes(lbuf2, lsize));
  92 +
  93                                 if (zio_decompress_data(c, pabd,
  94                                     lbuf, psize, lsize) == 0 &&
  95 -                                   zio_decompress_data_buf(c, pbuf2,
  96 +                                   zio_decompress_data(c, pabd,
  97                                     lbuf2, psize, lsize) == 0 &&
  98                                     bcmp(lbuf, lbuf2, lsize) == 0)
  99                                         break;
 100 @@ -4098,11 +4098,9 @@ zdb_read_block(char *thing, spa_t *spa)
 101                         if (c != ZIO_COMPRESS_FUNCTIONS)
 102                                 break;
 103                 }
 104 -
 105 -               umem_free(pbuf2, SPA_MAXBLOCKSIZE);
 106                 umem_free(lbuf2, SPA_MAXBLOCKSIZE);
 107
 108 -               if (lsize <= psize) {
 109 +               if (lsize > SPA_MAXBLOCKSIZE) {
 110                         (void) printf("Decompress of %s failed\n", thing);
 111                         goto out;
 112                 }
 113 diff --git a/man/man8/zdb.8 b/man/man8/zdb.8
 114 index 4e47de7be..d991aae4c 100644
 115 --- a/man/man8/zdb.8
 116 +++ b/man/man8/zdb.8
 117 @@ -246,7 +246,9 @@ and, optionally,
 118  .It Sy b Ar offset
 119  Print block pointer
 120  .It Sy d
 121 -Decompress the block
 122 +Decompress the block. Set environment variable
 123 +.Nm ZBD_NO_ZLE
 124 +to skip zle when guessing.
 125  .It Sy e
 126  Byte swap the block
 127  .It Sy g
 128 --
 129 2.14.2
 130