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target/user: Refactor data area allocation code
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Introduce alloc_and_scatter_data_area()/gather_and_free_data_area()
functions that allocate/deallocate space from the data area and copy
data to/from a given scatter-gather list. These functions are needed so
the next patch, introducing support for bidirectional commands in TCMU,
can use the same code path both for t_data_sg and for t_bidi_data_sg.

Signed-off-by: Ilias Tsitsimpis <[email protected]>
Signed-off-by: Vangelis Koukis <[email protected]>
Reviewed-by: Andy Grover <[email protected]>
Signed-off-by: Nicholas Bellinger <[email protected]>
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@iliastsi
iliastsi authored and Nicholas Bellinger committed May 31, 2015
1 parent b32bd0a commit f97ec7d
Showing 1 changed file with 106 additions and 83 deletions.
189 changes: 106 additions & 83 deletions drivers/target/target_core_user.c
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
/*
* Copyright (C) 2013 Shaohua Li <[email protected]>
* Copyright (C) 2014 Red Hat, Inc.
* Copyright (C) 2015 Arrikto, Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
Expand Down Expand Up @@ -224,9 +225,104 @@ static inline size_t head_to_end(size_t head, size_t size)

#define UPDATE_HEAD(head, used, size) smp_store_release(&head, ((head % size) + used) % size)

static void alloc_and_scatter_data_area(struct tcmu_dev *udev,
struct scatterlist *data_sg, unsigned int data_nents,
struct iovec **iov, int *iov_cnt, bool copy_data)
{
int i;
void *from, *to;
size_t copy_bytes;
struct scatterlist *sg;

for_each_sg(data_sg, sg, data_nents, i) {
copy_bytes = min_t(size_t, sg->length,
head_to_end(udev->data_head, udev->data_size));
from = kmap_atomic(sg_page(sg)) + sg->offset;
to = (void *) udev->mb_addr + udev->data_off + udev->data_head;

if (copy_data) {
memcpy(to, from, copy_bytes);
tcmu_flush_dcache_range(to, copy_bytes);
}

/* Even iov_base is relative to mb_addr */
(*iov)->iov_len = copy_bytes;
(*iov)->iov_base = (void __user *) udev->data_off +
udev->data_head;
(*iov_cnt)++;
(*iov)++;

UPDATE_HEAD(udev->data_head, copy_bytes, udev->data_size);

/* Uh oh, we wrapped the buffer. Must split sg across 2 iovs. */
if (sg->length != copy_bytes) {
from += copy_bytes;
copy_bytes = sg->length - copy_bytes;

(*iov)->iov_len = copy_bytes;
(*iov)->iov_base = (void __user *) udev->data_off +
udev->data_head;

if (copy_data) {
to = (void *) udev->mb_addr +
udev->data_off + udev->data_head;
memcpy(to, from, copy_bytes);
tcmu_flush_dcache_range(to, copy_bytes);
}

(*iov_cnt)++;
(*iov)++;

UPDATE_HEAD(udev->data_head,
copy_bytes, udev->data_size);
}

kunmap_atomic(from);
}
}

static void gather_and_free_data_area(struct tcmu_dev *udev,
struct scatterlist *data_sg, unsigned int data_nents)
{
int i;
void *from, *to;
size_t copy_bytes;
struct scatterlist *sg;

/* It'd be easier to look at entry's iovec again, but UAM */
for_each_sg(data_sg, sg, data_nents, i) {
copy_bytes = min_t(size_t, sg->length,
head_to_end(udev->data_tail, udev->data_size));

to = kmap_atomic(sg_page(sg)) + sg->offset;
WARN_ON(sg->length + sg->offset > PAGE_SIZE);
from = (void *) udev->mb_addr +
udev->data_off + udev->data_tail;
tcmu_flush_dcache_range(from, copy_bytes);
memcpy(to, from, copy_bytes);

UPDATE_HEAD(udev->data_tail, copy_bytes, udev->data_size);

/* Uh oh, wrapped the data buffer for this sg's data */
if (sg->length != copy_bytes) {
from = (void *) udev->mb_addr +
udev->data_off + udev->data_tail;
WARN_ON(udev->data_tail);
to += copy_bytes;
copy_bytes = sg->length - copy_bytes;
tcmu_flush_dcache_range(from, copy_bytes);
memcpy(to, from, copy_bytes);

UPDATE_HEAD(udev->data_tail,
copy_bytes, udev->data_size);
}
kunmap_atomic(to);
}
}

/*
* We can't queue a command until we have space available on the cmd ring *and* space
* space avail on the data ring.
* We can't queue a command until we have space available on the cmd ring *and*
* space available on the data ring.
*
* Called with ring lock held.
*/
Expand Down Expand Up @@ -274,12 +370,11 @@ static int tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
size_t base_command_size, command_size;
struct tcmu_mailbox *mb;
struct tcmu_cmd_entry *entry;
int i;
struct scatterlist *sg;
struct iovec *iov;
int iov_cnt = 0;
int iov_cnt;
uint32_t cmd_head;
uint64_t cdb_off;
bool copy_to_data_area;

if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags))
return -EINVAL;
Expand Down Expand Up @@ -360,49 +455,10 @@ static int tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
* Fix up iovecs, and handle if allocation in data ring wrapped.
*/
iov = &entry->req.iov[0];
for_each_sg(se_cmd->t_data_sg, sg, se_cmd->t_data_nents, i) {
size_t copy_bytes = min((size_t)sg->length,
head_to_end(udev->data_head, udev->data_size));
void *from = kmap_atomic(sg_page(sg)) + sg->offset;
void *to = (void *) mb + udev->data_off + udev->data_head;

if (tcmu_cmd->se_cmd->data_direction == DMA_TO_DEVICE) {
memcpy(to, from, copy_bytes);
tcmu_flush_dcache_range(to, copy_bytes);
}

/* Even iov_base is relative to mb_addr */
iov->iov_len = copy_bytes;
iov->iov_base = (void __user *) udev->data_off +
udev->data_head;
iov_cnt++;
iov++;

UPDATE_HEAD(udev->data_head, copy_bytes, udev->data_size);

/* Uh oh, we wrapped the buffer. Must split sg across 2 iovs. */
if (sg->length != copy_bytes) {
from += copy_bytes;
copy_bytes = sg->length - copy_bytes;

iov->iov_len = copy_bytes;
iov->iov_base = (void __user *) udev->data_off +
udev->data_head;

if (se_cmd->data_direction == DMA_TO_DEVICE) {
to = (void *) mb + udev->data_off + udev->data_head;
memcpy(to, from, copy_bytes);
tcmu_flush_dcache_range(to, copy_bytes);
}

iov_cnt++;
iov++;

UPDATE_HEAD(udev->data_head, copy_bytes, udev->data_size);
}

kunmap_atomic(from);
}
iov_cnt = 0;
copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE);
alloc_and_scatter_data_area(udev, se_cmd->t_data_sg,
se_cmd->t_data_nents, &iov, &iov_cnt, copy_to_data_area);
entry->req.iov_cnt = iov_cnt;
entry->req.iov_bidi_cnt = 0;
entry->req.iov_dif_cnt = 0;
Expand Down Expand Up @@ -481,41 +537,8 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
}
else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
struct scatterlist *sg;
int i;

/* It'd be easier to look at entry's iovec again, but UAM */
for_each_sg(se_cmd->t_data_sg, sg, se_cmd->t_data_nents, i) {
size_t copy_bytes;
void *to;
void *from;

copy_bytes = min((size_t)sg->length,
head_to_end(udev->data_tail, udev->data_size));

to = kmap_atomic(sg_page(sg)) + sg->offset;
WARN_ON(sg->length + sg->offset > PAGE_SIZE);
from = (void *) udev->mb_addr + udev->data_off + udev->data_tail;
tcmu_flush_dcache_range(from, copy_bytes);
memcpy(to, from, copy_bytes);

UPDATE_HEAD(udev->data_tail, copy_bytes, udev->data_size);

/* Uh oh, wrapped the data buffer for this sg's data */
if (sg->length != copy_bytes) {
from = (void *) udev->mb_addr + udev->data_off + udev->data_tail;
WARN_ON(udev->data_tail);
to += copy_bytes;
copy_bytes = sg->length - copy_bytes;
tcmu_flush_dcache_range(from, copy_bytes);
memcpy(to, from, copy_bytes);

UPDATE_HEAD(udev->data_tail, copy_bytes, udev->data_size);
}

kunmap_atomic(to);
}

gather_and_free_data_area(udev,
se_cmd->t_data_sg, se_cmd->t_data_nents);
} else if (se_cmd->data_direction == DMA_TO_DEVICE) {
UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
} else if (se_cmd->data_direction != DMA_NONE) {
Expand Down

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