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bdev: cleanup child iov rewind code

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When we run out of bdev_io's child iovs and we had
to round down I/O size to nearest block size boundary,
we used to decrease the existing child_iovcnt and
set a new "child_iov_run_out" flag to terminate the
uppermost splitting loop.

We can get rid of that new flag by just not decreasing
child_iovcnt when rewinding the last few iovs - it
will make the uppermost loop naturally terminate using
the existing checks.

Change-Id: Ie40c7ce135e7fb8fe284afdf7beeebd10af85cb7
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/459911
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
This commit is contained in:
Darek Stojaczyk 2019-07-01 06:43:05 +02:00 committed by Ben Walker
parent 5926236661
commit fcbbcf4905
1 changed files with 8 additions and 11 deletions
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19
lib/bdev/bdev.c
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@ -1601,7 +1601,6 @@ _spdk_bdev_io_split(void *_bdev_io)
uint64_t parent_iov_offset, iov_len;
uint32_t parent_iovpos, parent_iovcnt, child_iovcnt, iovcnt;
void *md_buf = NULL;
bool child_iov_run_out = false;
int rc;
remaining = bdev_io->u.bdev.split_remaining_num_blocks;
@ -1657,16 +1656,19 @@ _spdk_bdev_io_split(void *_bdev_io)
* size and then adjust to_next_boundary before starting the
* child I/O.
*/
assert(child_iovcnt == BDEV_IO_NUM_CHILD_IOV);
to_last_block_bytes = to_next_boundary_bytes % blocklen;
if (to_last_block_bytes != 0) {
to_next_boundary_bytes += _to_next_boundary(to_next_boundary_bytes, blocklen);;
uint32_t child_iovpos = child_iovcnt - 1;
/* don't decrease child_iovcnt so the loop will naturally end */
to_next_boundary_bytes += _to_next_boundary(to_next_boundary_bytes, blocklen);
while (to_last_block_bytes > 0 && iovcnt > 0) {
iov_len = spdk_min(to_last_block_bytes,
bdev_io->child_iov[child_iovcnt - 1].iov_len);
bdev_io->child_iov[child_iovcnt - 1].iov_len -= iov_len;
if (bdev_io->child_iov[child_iovcnt - 1].iov_len == 0) {
child_iovcnt--;
bdev_io->child_iov[child_iovpos].iov_len);
bdev_io->child_iov[child_iovpos].iov_len -= iov_len;
if (bdev_io->child_iov[child_iovpos].iov_len == 0) {
child_iovpos--;
iovcnt--;
}
to_last_block_bytes -= iov_len;
@ -1674,7 +1676,6 @@ _spdk_bdev_io_split(void *_bdev_io)
assert(to_last_block_bytes == 0);
}
child_iov_run_out = true;
to_next_boundary -= to_next_boundary_bytes / blocklen;
}
@ -1699,10 +1700,6 @@ _spdk_bdev_io_split(void *_bdev_io)
remaining -= to_next_boundary;
bdev_io->u.bdev.split_current_offset_blocks = current_offset;
bdev_io->u.bdev.split_remaining_num_blocks = remaining;
/* stop splitting until child_iov is available */
if (spdk_unlikely(child_iov_run_out)) {
return;
}
} else {
bdev_io->u.bdev.split_outstanding--;
if (rc == -ENOMEM) {