scsi: target: tcmu: Join tcmu_cmd_get_data_length() and tcmu_cmd_get_block_cnt()

Simplify code by joining tcmu_cmd_get_data_length() and
tcmu_cmd_get_block_cnt() into tcmu_cmd_set_block_cnts().  The new function
sets tcmu_cmd->dbi_cnt and also the new field tcmu_cmd->dbi_bidi_cnt which
is needed for further enhancements in following patches.  Simplify some
code by using tcmu_cmd->dbi(_bidi)_cnt instead of calculation from length.

Please note: The calculation of the number of dbis needed for bidi was
wrong. It was based on the length of the first bidi sg only. I changed it
to correctly sum up entire length of all bidi sgs.

Link: https://lore.kernel.org/r/20200910155041.17654-2-bstroesser@ts.fujitsu.com
Acked-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 9775670..411172d 100644 (file)
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -177,6 +177,7 @@ struct tcmu_cmd {
        /* Can't use se_cmd when cleaning up expired cmds, because if
           cmd has been completed then accessing se_cmd is off limits */
        uint32_t dbi_cnt;
+       uint32_t dbi_bidi_cnt;
        uint32_t dbi_cur;
        uint32_t *dbi;
 
@@ -558,25 +559,20 @@ static inline void tcmu_free_cmd(struct tcmu_cmd *tcmu_cmd)
        kmem_cache_free(tcmu_cmd_cache, tcmu_cmd);
 }
 
-static inline size_t tcmu_cmd_get_data_length(struct tcmu_cmd *tcmu_cmd)
+static inline void tcmu_cmd_set_block_cnts(struct tcmu_cmd *cmd)
 {
-       struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
-       size_t data_length = round_up(se_cmd->data_length, DATA_BLOCK_SIZE);
+       int i, len;
+       struct se_cmd *se_cmd = cmd->se_cmd;
+
+       cmd->dbi_cnt = DIV_ROUND_UP(se_cmd->data_length, DATA_BLOCK_SIZE);
 
        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
-               data_length += round_up(se_cmd->t_bidi_data_sg->length,
-                               DATA_BLOCK_SIZE);
+               for (i = 0, len = 0; i < se_cmd->t_bidi_data_nents; i++)
+                       len += se_cmd->t_bidi_data_sg[i].length;
+               cmd->dbi_bidi_cnt = DIV_ROUND_UP(len, DATA_BLOCK_SIZE);
+               cmd->dbi_cnt += cmd->dbi_bidi_cnt;
        }
-
-       return data_length;
-}
-
-static inline uint32_t tcmu_cmd_get_block_cnt(struct tcmu_cmd *tcmu_cmd)
-{
-       size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);
-
-       return data_length / DATA_BLOCK_SIZE;
 }
 
 static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
@@ -593,8 +589,7 @@ static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
        tcmu_cmd->se_cmd = se_cmd;
        tcmu_cmd->tcmu_dev = udev;
 
-       tcmu_cmd_reset_dbi_cur(tcmu_cmd);
-       tcmu_cmd->dbi_cnt = tcmu_cmd_get_block_cnt(tcmu_cmd);
+       tcmu_cmd_set_block_cnts(tcmu_cmd);
        tcmu_cmd->dbi = kcalloc(tcmu_cmd->dbi_cnt, sizeof(uint32_t),
                                GFP_NOIO);
        if (!tcmu_cmd->dbi) {
@@ -767,13 +762,12 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                data_sg = se_cmd->t_data_sg;
                data_nents = se_cmd->t_data_nents;
        } else {
-
                /*
                 * For bidi case, the first count blocks are for Data-Out
                 * buffer blocks, and before gathering the Data-In buffer
-                * the Data-Out buffer blocks should be discarded.
+                * the Data-Out buffer blocks should be skipped.
                 */
-               count = DIV_ROUND_UP(se_cmd->data_length, DATA_BLOCK_SIZE);
+               count = cmd->dbi_cnt - cmd->dbi_bidi_cnt;
 
                data_sg = se_cmd->t_bidi_data_sg;
                data_nents = se_cmd->t_bidi_data_nents;
@@ -827,11 +821,9 @@ static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh)
  * Called with ring lock held.
  */
 static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
-               size_t cmd_size, size_t data_needed)
+                               size_t cmd_size)
 {
        struct tcmu_mailbox *mb = udev->mb_addr;
-       uint32_t blocks_needed = (data_needed + DATA_BLOCK_SIZE - 1)
-                               / DATA_BLOCK_SIZE;
        size_t space, cmd_needed;
        u32 cmd_head;
 
@@ -855,23 +847,23 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                return false;
        }
 
-       if (!data_needed)
+       if (!cmd || !cmd->dbi_cnt)
                return true;
 
        /* try to check and get the data blocks as needed */
        space = spc_bitmap_free(udev->data_bitmap, udev->dbi_thresh);
-       if ((space * DATA_BLOCK_SIZE) < data_needed) {
+       if (space < cmd->dbi_cnt) {
                unsigned long blocks_left =
                                (udev->max_blocks - udev->dbi_thresh) + space;
 
-               if (blocks_left < blocks_needed) {
+               if (blocks_left < cmd->dbi_cnt) {
                        pr_debug("no data space: only %lu available, but ask for %zu\n",
                                        blocks_left * DATA_BLOCK_SIZE,
-                                       data_needed);
+                                       cmd->dbi_cnt * DATA_BLOCK_SIZE);
                        return false;
                }
 
-               udev->dbi_thresh += blocks_needed;
+               udev->dbi_thresh += cmd->dbi_cnt;
                if (udev->dbi_thresh > udev->max_blocks)
                        udev->dbi_thresh = udev->max_blocks;
        }
@@ -990,7 +982,8 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
        uint32_t cmd_head;
        uint64_t cdb_off;
        bool copy_to_data_area;
-       size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);
+       /* size of data buffer needed */
+       size_t data_length = (size_t)tcmu_cmd->dbi_cnt * DATA_BLOCK_SIZE;
 
        *scsi_err = TCM_NO_SENSE;
 
@@ -1031,7 +1024,7 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
                return -1;
        }
 
-       if (!is_ring_space_avail(udev, tcmu_cmd, command_size, data_length)) {
+       if (!is_ring_space_avail(udev, tcmu_cmd, command_size)) {
                /*
                 * Don't leave commands partially setup because the unmap
                 * thread might need the blocks to make forward progress.
@@ -1145,7 +1138,7 @@ queue_tmr_ring(struct tcmu_dev *udev, struct tcmu_tmr *tmr)
        cmd_size = round_up(sizeof(*entry) + id_list_sz, TCMU_OP_ALIGN_SIZE);
 
        if (!list_empty(&udev->tmr_queue) ||
-           !is_ring_space_avail(udev, NULL, cmd_size, 0)) {
+           !is_ring_space_avail(udev, NULL, cmd_size)) {
                list_add_tail(&tmr->queue_entry, &udev->tmr_queue);
                pr_debug("adding tmr %p on dev %s to TMR ring space wait queue\n",
                         tmr, udev->name);