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LD_SCSI: Introduce get_lba_status in read()

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For large continous reads I may be benifical to check if the blocks
that are going to be read are allocated. If they are not allocated
they do not need to be read which massivly speeds up the read.

This behaviour is optional and can be turned on with environment
variable LD_ISCSI_GET_LBA_STATUS=1
This commit is contained in:
Peter Lieven
2012-10-21 09:24:19 +02:00
parent 08bfabcd36
commit bfac1f85a3
1 changed files with 57 additions and 2 deletions
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59
src/ld_iscsi.c
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@@ -51,6 +51,7 @@ struct iscsi_fd_list {
uint64_t num_blocks;
off_t offset;
mode_t mode;
int get_lba_status;
};
static struct iscsi_fd_list iscsi_fd_list[ISCSI_MAX_FD];
@@ -148,6 +149,14 @@ int open(const char *path, int flags, mode_t mode)
iscsi_fd_list[fd].lun = iscsi_url->lun;
iscsi_fd_list[fd].mode = mode;
if (getenv("LD_ISCSI_GET_LBA_STATUS") != NULL) {
iscsi_fd_list[fd].get_lba_status = atoi(getenv("LD_ISCSI_GET_LBA_STATUS"));
if (rc16->lbpme == 0){
LD_ISCSI_DPRINTF(1,"Logical unit is fully provisioned. Will skip get_lba_status tasks");
iscsi_fd_list[fd].get_lba_status = 0;
}
}
scsi_free_scsi_task(task);
iscsi_destroy_url(iscsi_url);
@@ -272,6 +281,7 @@ ssize_t read(int fd, void *buf, size_t count)
uint64_t offset;
uint64_t num_blocks, lba;
struct scsi_task *task;
struct scsi_get_lba_status *lbas;
if (iscsi_fd_list[fd].dup2fd >= 0) {
return read(iscsi_fd_list[fd].dup2fd, buf, count);
@@ -290,13 +300,58 @@ ssize_t read(int fd, void *buf, size_t count)
count = num_blocks * iscsi_fd_list[fd].block_size;
}
iscsi_fd_list[fd].in_flight = 1;
if (iscsi_fd_list[fd].get_lba_status != 0) {
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) {
LD_ISCSI_DPRINTF(0,"failed to send get_lba_status command");
iscsi_fd_list[fd].in_flight = 0;
errno = EIO;
return -1;
}
lbas = scsi_datain_unmarshall(task);
if (lbas == NULL) {
LD_ISCSI_DPRINTF(0,"failed to unmarshall get_lba_status data");
scsi_free_scsi_task(task);
iscsi_fd_list[fd].in_flight = 0;
errno = EIO;
return -1;
}
u_int32_t i;
LD_ISCSI_DPRINTF(5,"get_lba_status: num_descriptors: %d",lbas->num_descriptors);
u_int32_t _num_allocated=0;
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);
if (lbasd->lba != _num_blocks+lba) {
LD_ISCSI_DPRINTF(0,"get_lba_status response is non-continuous");
scsi_free_scsi_task(task);
iscsi_fd_list[fd].in_flight = 0;
errno = EIO;
return -1;
}
_num_allocated+=(lbasd->provisioning==0x00)?lbasd->num_blocks:0;
_num_blocks+=lbasd->num_blocks;
}
scsi_free_scsi_task(task);
if (_num_allocated == 0 && _num_blocks >= 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,"read16_sync: 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);
iscsi_fd_list[fd].in_flight = 1;
task = iscsi_read16_sync(iscsi_fd_list[fd].iscsi, iscsi_fd_list[fd].lun, lba, num_blocks * iscsi_fd_list[fd].block_size, iscsi_fd_list[fd].block_size, 0, 0, 0, 0, 0);
iscsi_fd_list[fd].in_flight = 0;
if (task == NULL || task->status != SCSI_STATUS_GOOD) {
LD_ISCSI_DPRINTF(0,"failed to send read10 command");
LD_ISCSI_DPRINTF(0,"failed to send read16 command");
errno = EIO;
return -1;
}