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tcmu: simplify dbi thresh handling 

We do not really save a lot by trying to increase thresh
a multiple of the existing value. This just simplifies the
code by increasing it to whatever is needed for the command
being executed.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Mike Christie 2017-11-28 12:40:38 -06:00 committed by Nicholas Bellinger
parent 6fd0ce7972
commit f890f5799a
1 changed files with 3 additions and 19 deletions
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22
drivers/target/target_core_user.c
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@ -79,7 +79,6 @@
#define DATA_BLOCK_SIZE PAGE_SIZE
#define DATA_BLOCK_BITS (256 * 1024)
#define DATA_SIZE (DATA_BLOCK_BITS * DATA_BLOCK_SIZE)
#define DATA_BLOCK_INIT_BITS 128
/* The total size of the ring is 8M + 256K * PAGE_SIZE */
#define TCMU_RING_SIZE (CMDR_SIZE + DATA_SIZE)
@ -700,7 +699,6 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
if ((space * DATA_BLOCK_SIZE) < data_needed) {
unsigned long blocks_left = DATA_BLOCK_BITS - udev->dbi_thresh +
space;
unsigned long grow;
if (blocks_left < blocks_needed) {
pr_debug("no data space: only %lu available, but ask for %zu\n",
@ -709,23 +707,9 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
return false;
}
/* Try to expand the thresh */
if (!udev->dbi_thresh) {
/* From idle state */
uint32_t init_thresh = DATA_BLOCK_INIT_BITS;
udev->dbi_thresh = max(blocks_needed, init_thresh);
} else {
/*
* Grow the data area by max(blocks needed,
* dbi_thresh / 2), but limited to the max
* DATA_BLOCK_BITS size.
*/
grow = max(blocks_needed, udev->dbi_thresh / 2);
udev->dbi_thresh += grow;
if (udev->dbi_thresh > DATA_BLOCK_BITS)
udev->dbi_thresh = DATA_BLOCK_BITS;
}
udev->dbi_thresh += blocks_needed;
if (udev->dbi_thresh > DATA_BLOCK_BITS)
udev->dbi_thresh = DATA_BLOCK_BITS;
}
return tcmu_get_empty_blocks(udev, cmd);