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LD_ISCSI: cache last result of get_lba_status

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get_lba_status returns provisioning for a range of blocks starting
from given lba. Especially for sequential reads its likely that
the next block read is already covered by the last result.

In case there is write support added to ld_iscsi there needs
to be an invalidation code for the cache.
This commit is contained in:
Peter Lieven
2012-10-21 20:29:39 +02:00
parent bfac1f85a3
commit afc963c312
1 changed files with 16 additions and 1 deletions
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17
src/ld_iscsi.c
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@@ -52,6 +52,8 @@ struct iscsi_fd_list {
off_t offset;
mode_t mode;
int get_lba_status;
struct scsi_lba_status_descriptor lbasd_cached;
int lbasd_cache_valid;
};
static struct iscsi_fd_list iscsi_fd_list[ISCSI_MAX_FD];
@@ -302,6 +304,17 @@ ssize_t read(int fd, void *buf, size_t count)
iscsi_fd_list[fd].in_flight = 1;
if (iscsi_fd_list[fd].get_lba_status != 0) {
if (iscsi_fd_list[fd].lbasd_cache_valid==1) {
LD_ISCSI_DPRINTF(5,"cached get_lba_status_descriptor is lba %lu, num_blocks %d, provisioning %d",iscsi_fd_list[fd].lbasd_cached.lba,iscsi_fd_list[fd].lbasd_cached.num_blocks,iscsi_fd_list[fd].lbasd_cached.provisioning);
if (iscsi_fd_list[fd].lbasd_cached.provisioning != 0x00 && lba >= iscsi_fd_list[fd].lbasd_cached.lba && lba+num_blocks < iscsi_fd_list[fd].lbasd_cached.lba+iscsi_fd_list[fd].lbasd_cached.num_blocks)
{
LD_ISCSI_DPRINTF(4,"skipped read16_sync for non-allocated blocks: lun %d, lba %lu, num_blocks: %lu, block_size: %d, offset: %lu count: %lu",iscsi_fd_list[fd].lun,lba,num_blocks,iscsi_fd_list[fd].block_size,offset,count);
memset(buf, 0x00, count);
iscsi_fd_list[fd].offset += count;
iscsi_fd_list[fd].in_flight = 0;
return count;
}
}
LD_ISCSI_DPRINTF(4,"get_lba_status_sync: lun %d, lba %lu, num_blocks: %lu",iscsi_fd_list[fd].lun,lba,num_blocks);
task = iscsi_get_lba_status_sync(iscsi_fd_list[fd].iscsi, iscsi_fd_list[fd].lun, lba, 8+16);
if (task == NULL || task->status != SCSI_STATUS_GOOD) {
@@ -325,7 +338,7 @@ ssize_t read(int fd, void *buf, size_t count)
u_int32_t _num_blocks=0;
for (i=0;i<lbas->num_descriptors;i++) {
struct scsi_lba_status_descriptor *lbasd = &lbas->descriptors[i];
LD_ISCSI_DPRINTF(5,"get_lba_status_descriptor %d, lba %lu, num_blocks %d, type %d",i,lbasd->lba,lbasd->num_blocks,lbasd->provisioning);
LD_ISCSI_DPRINTF(5,"get_lba_status_descriptor %d, lba %lu, num_blocks %d, provisioning %d",i,lbasd->lba,lbasd->num_blocks,lbasd->provisioning);
if (lbasd->lba != _num_blocks+lba) {
LD_ISCSI_DPRINTF(0,"get_lba_status response is non-continuous");
scsi_free_scsi_task(task);
@@ -335,6 +348,8 @@ ssize_t read(int fd, void *buf, size_t count)
}
_num_allocated+=(lbasd->provisioning==0x00)?lbasd->num_blocks:0;
_num_blocks+=lbasd->num_blocks;
iscsi_fd_list[fd].lbasd_cached=lbas->descriptors[i];
iscsi_fd_list[fd].lbasd_cache_valid=1;
}
scsi_free_scsi_task(task);
if (_num_allocated == 0 && _num_blocks >= num_blocks) {