simplify-some-code-in-read-mmp_block

   1 ext4: simplify some code in read_mmp_block()
   2
   3 From: Dan Carpenter <dan.carpenter@oracle.com>
   4
   5 My static check complains because we have:
   6
   7         if (!*bh)
   8                 return -ENOMEM;
   9         if (*bh) {
  10
  11 The second check is unnecessary.
  12
  13 I've simplified this code by moving the "if (!*bh)" checks around.  Also
  14 Andreas Dilger says we should probably print a warning if sb_getblk()
  15 fails.
  16
  17 [ Restructured the code so that we print a warning message as well if
  18   the mmp block doesn't check out, and to print the error code to
  19   disambiguate between the error cases.  - TYT ]
  20
  21 Reviewed-by: Andreas Dilger <adilger@dilger.ca>
  22 Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
  23 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  24 ---
  25  fs/ext4/mmp.c | 46 +++++++++++++++++++++++++---------------------
  26  1 file changed, 25 insertions(+), 21 deletions(-)
  27
  28 diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
  29 index 8313ca3..048c52a 100644
  30 --- a/fs/ext4/mmp.c
  31 +++ b/fs/ext4/mmp.c
  32 @@ -69,6 +69,7 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
  33                           ext4_fsblk_t mmp_block)
  34  {
  35         struct mmp_struct *mmp;
  36 +       int ret;
  37
  38         if (*bh)
  39                 clear_buffer_uptodate(*bh);
  40 @@ -76,33 +77,36 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
  41         /* This would be sb_bread(sb, mmp_block), except we need to be sure
  42          * that the MD RAID device cache has been bypassed, and that the read
  43          * is not blocked in the elevator. */
  44 -       if (!*bh)
  45 +       if (!*bh) {
  46                 *bh = sb_getblk(sb, mmp_block);
  47 -       if (!*bh)
  48 -               return -ENOMEM;
  49 -       if (*bh) {
  50 -               get_bh(*bh);
  51 -               lock_buffer(*bh);
  52 -               (*bh)->b_end_io = end_buffer_read_sync;
  53 -               submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh);
  54 -               wait_on_buffer(*bh);
  55 -               if (!buffer_uptodate(*bh)) {
  56 -                       brelse(*bh);
  57 -                       *bh = NULL;
  58 +               if (!*bh) {
  59 +                       ret = -ENOMEM;
  60 +                       goto warn_exit;
  61                 }
  62         }
  63 -       if (unlikely(!*bh)) {
  64 -               ext4_warning(sb, "Error while reading MMP block %llu",
  65 -                            mmp_block);
  66 -               return -EIO;
  67 +
  68 +       get_bh(*bh);
  69 +       lock_buffer(*bh);
  70 +       (*bh)->b_end_io = end_buffer_read_sync;
  71 +       submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh);
  72 +       wait_on_buffer(*bh);
  73 +       if (!buffer_uptodate(*bh)) {
  74 +               brelse(*bh);
  75 +               *bh = NULL;
  76 +               ret = -EIO;
  77 +               goto warn_exit;
  78         }
  79
  80         mmp = (struct mmp_struct *)((*bh)->b_data);
  81 -       if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
  82 -           !ext4_mmp_csum_verify(sb, mmp))
  83 -               return -EINVAL;
  84 -
  85 -       return 0;
  86 +       if (le32_to_cpu(mmp->mmp_magic) == EXT4_MMP_MAGIC &&
  87 +           ext4_mmp_csum_verify(sb, mmp))
  88 +               return 0;
  89 +       ret = -EINVAL;
  90 +
  91 +warn_exit:
  92 +       ext4_warning(sb, "Error %d while reading MMP block %llu",
  93 +                    ret, mmp_block);
  94 +       return ret;
  95  }
  96
  97  /*