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scst: Micro-optimize the overflow checks in scst_tape_generic_parse()

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Use shift operations instead of multiplication operations. See also commit
6258844d60 ("scst: fix overflows handling for tapes").


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@9331 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2021-01-10 01:17:29 +00:00
parent 5d630c2514
commit 94a84adbf7
1 changed files with 12 additions and 16 deletions
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28
scst/src/scst_lib.c
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@@ -12441,21 +12441,20 @@ int scst_tape_generic_parse(struct scst_cmd *cmd)
*/
if (cmd->op_flags & SCST_TRANSFER_LEN_TYPE_FIXED && cmd->cdb[1] & 1) {
int block_size = cmd->dev->block_size;
uint64_t b, ob;
bool overflow;
uint32_t block_size = cmd->dev->block_size;
uint32_t block_shift = cmd->dev->block_shift;
bool overflow = shift_left_overflows(cmd->bufflen, block_shift) ||
shift_left_overflows(cmd->data_len, block_shift) ||
shift_left_overflows(cmd->out_bufflen, block_shift);
b = ((uint64_t)cmd->bufflen) * block_size;
ob = ((uint64_t)cmd->out_bufflen) * block_size;
overflow = (b > 0xFFFFFFFF) ||
(ob > 0xFFFFFFFF);
BUILD_BUG_ON(sizeof(cmd->bufflen) != 4);
BUILD_BUG_ON(sizeof(cmd->out_bufflen) != 4);
if (unlikely(overflow)) {
PRINT_WARNING("bufflen %u, data_len %llu or out_bufflen"
" %u too large for device %s (block size"
" %u, b %llu, ob %llu)", cmd->bufflen,
" %u)", cmd->bufflen,
cmd->data_len, cmd->out_bufflen,
cmd->dev->virt_name, block_size, b, ob);
cmd->dev->virt_name, block_size);
PRINT_BUFFER("CDB", cmd->cdb, cmd->cdb_len);
scst_set_cmd_error(cmd, SCST_LOAD_SENSE(
scst_sense_block_out_range_error));
@@ -12463,12 +12462,9 @@ int scst_tape_generic_parse(struct scst_cmd *cmd)
goto out;
}
cmd->bufflen = b;
cmd->out_bufflen = ob;
/* cmd->data_len is 64-bit, so can't overflow here */
BUILD_BUG_ON(sizeof(cmd->data_len) < 8);
cmd->data_len *= block_size;
cmd->bufflen <<= block_shift;
cmd->out_bufflen <<= block_shift;
cmd->data_len <<= block_shift;
}
if ((cmd->op_flags & (SCST_SMALL_TIMEOUT | SCST_LONG_TIMEOUT)) == 0)