struct block *blist_clone(struct block *blist, int header_len, int len,
uint32_t offset)
{
int ret;
struct block *newb = block_alloc(header_len, MEM_WAIT);
do {
ret = __blist_clone_to(blist, newb, len, offset);
if (ret)
block_add_extd(newb, ret, MEM_WAIT);
} while (ret);
return newb;
}
/* given a queue, makes a single block with header_len reserved space in the
* block main body, and the contents of [offset, len + offset) pointed to in the
* new blocks ext_data. */
struct block *qclone(struct queue *q, int header_len, int len, uint32_t offset)
{
int ret;
struct block *newb = block_alloc(header_len, MEM_WAIT);
/* the while loop should rarely be used: it would require someone
* concurrently adding to the queue. */
do {
/* TODO: RCU: protecting the q list (b->next) (need read lock) */
spin_lock_irqsave(&q->lock);
ret = __blist_clone_to(q->bfirst, newb, len, offset);
spin_unlock_irqsave(&q->lock);
if (ret)
block_add_extd(newb, ret, MEM_WAIT);
} while (ret);
return newb;
}
/*
* write to a queue. only Maxatomic bytes at a time is atomic.
*/
int qwrite(struct queue *q, void *vp, int len)
{
int n, sofar;
struct block *b;
uint8_t *p = vp;
void *ext_buf;
QDEBUG if (!islo())
printd("qwrite hi %p\n", getcallerpc(&q));
sofar = 0;
do {
n = len - sofar;
/* This is 64K, the max amount per single block. Still a good value? */
if (n > Maxatomic)
n = Maxatomic;
/* If n is small, we don't need to bother with the extra_data. But
* until the whole stack can handle extd blocks, we'll use them
* unconditionally. */
#ifdef CONFIG_BLOCK_EXTRAS
/* allocb builds in 128 bytes of header space to all blocks, but this is
* only available via padblock (to the left). we also need some space
* for pullupblock for some basic headers (like icmp) that get written
* in directly */
b = allocb(64);
ext_buf = kmalloc(n, 0);
memcpy(ext_buf, p + sofar, n);
block_add_extd(b, 1, KMALLOC_WAIT); /* returns 0 on success */
b->extra_data[0].base = (uintptr_t)ext_buf;
b->extra_data[0].off = 0;
b->extra_data[0].len = n;
b->extra_len += n;
#else
b = allocb(n);
memmove(b->wp, p + sofar, n);
b->wp += n;
#endif
qbwrite(q, b);
sofar += n;
} while (sofar < len && (q->state & Qmsg) == 0);
return len;
}
/* Append an extra data buffer @base with offset @off of length @len to block
* @b. Reuse an unused extra data slot if there's any.
* Return 0 on success or -1 on error. */
int block_append_extra(struct block *b, uintptr_t base, uint32_t off,
uint32_t len, int mem_flags)
{
unsigned int nr_bufs = b->nr_extra_bufs + 1;
struct extra_bdata *ebd;
ebd = next_unused_slot(b);
if (!ebd) {
if (block_add_extd(b, nr_bufs, mem_flags) != 0)
return -1;
ebd = next_unused_slot(b);
assert(ebd);
}
ebd->base = base;
ebd->off = off;
ebd->len = len;
b->extra_len += ebd->len;
return 0;
}
/* Helper, allocs a block and copies [from, from + len) into it. Returns the
* block on success, 0 on failure. */
static struct block *build_block(void *from, size_t len, int mem_flags)
{
struct block *b;
void *ext_buf;
/* If len is small, we don't need to bother with the extra_data. But until
* the whole stack can handle extd blocks, we'll use them unconditionally.
* */
#ifdef CONFIG_BLOCK_EXTRAS
/* allocb builds in 128 bytes of header space to all blocks, but this is
* only available via padblock (to the left). we also need some space
* for pullupblock for some basic headers (like icmp) that get written
* in directly */
b = block_alloc(64, mem_flags);
if (!b)
return 0;
ext_buf = kmalloc(len, mem_flags);
if (!ext_buf) {
kfree(b);
return 0;
}
memcpy(ext_buf, from, len);
if (block_add_extd(b, 1, mem_flags)) {
kfree(ext_buf);
kfree(b);
return 0;
}
b->extra_data[0].base = (uintptr_t)ext_buf;
b->extra_data[0].off = 0;
b->extra_data[0].len = len;
b->extra_len += len;
#else
b = block_alloc(n, mem_flags);
if (!b)
return 0;
memmove(b->wp, from, len);
b->wp += len;
#endif
return b;
}
/* given a string of blocks, fills the new block's extra_data with the contents
* of the blist [offset, len + offset)
*
* returns 0 on success. the only failure is if the extra_data array was too
* small, so this returns a positive integer saying how big the extra_data needs
* to be.
*
* callers are responsible for protecting the list structure. */
static int __blist_clone_to(struct block *blist, struct block *newb, int len,
uint32_t offset)
{
struct block *b, *first;
unsigned int nr_bufs = 0;
unsigned int b_idx, newb_idx = 0;
uint8_t *first_main_body = 0;
/* find the first block; keep offset relative to the latest b in the list */
for (b = blist; b; b = b->next) {
if (BLEN(b) > offset)
break;
offset -= BLEN(b);
}
/* qcopy semantics: if you asked for an offset outside the block list, you
* get an empty block back */
if (!b)
return 0;
first = b;
/* upper bound for how many buffers we'll need in newb */
for (/* b is set*/; b; b = b->next) {
nr_bufs += 1 + b->nr_extra_bufs; /* 1 for the main body */
}
/* we might be holding a spinlock here, so we won't wait for kmalloc */
if (block_add_extd(newb, nr_bufs, 0) != 0) {
/* caller will need to alloc these, then re-call us */
return nr_bufs;
}
for (b = first; b && len; b = b->next) {
b_idx = 0;
if (offset) {
if (offset < BHLEN(b)) {
/* off is in the main body */
len -= point_to_body(b, b->rp + offset, newb, newb_idx, len);
newb_idx++;
} else {
/* off is in one of the buffers (or just past the last one).
* we're not going to point to b's main body at all. */
offset -= BHLEN(b);
assert(b->extra_data);
/* assuming these extrabufs are packed, or at least that len
* isn't gibberish */
while (b->extra_data[b_idx].len <= offset) {
offset -= b->extra_data[b_idx].len;
b_idx++;
}
/* now offset is set to our offset in the b_idx'th buf */
len -= point_to_buf(b, b_idx, offset, newb, newb_idx, len);
newb_idx++;
b_idx++;
}
offset = 0;
} else {
len -= point_to_body(b, b->rp, newb, newb_idx, len);
newb_idx++;
}
/* knock out all remaining bufs. we only did one point_to_ op by now,
* and any point_to_ could be our last if it consumed all of len. */
for (int i = b_idx; (i < b->nr_extra_bufs) && len; i++) {
len -= point_to_buf(b, i, 0, newb, newb_idx, len);
newb_idx++;
}
}
return 0;
}