static int
shm_dotruncate(struct shmfd *shmfd, off_t length)
{
vm_object_t object;
vm_page_t m;
vm_pindex_t nobjsize;
vm_ooffset_t delta;
object = shmfd->shm_object;
VM_OBJECT_LOCK(object);
if (length == shmfd->shm_size) {
VM_OBJECT_UNLOCK(object);
return (0);
}
nobjsize = OFF_TO_IDX(length + PAGE_MASK);
/* Are we shrinking? If so, trim the end. */
if (length < shmfd->shm_size) {
delta = ptoa(object->size - nobjsize);
/* Toss in memory pages. */
if (nobjsize < object->size)
vm_object_page_remove(object, nobjsize, object->size,
FALSE);
/* Toss pages from swap. */
if (object->type == OBJT_SWAP)
swap_pager_freespace(object, nobjsize, delta);
/* Free the swap accounted for shm */
swap_release_by_uid(delta, object->uip);
object->charge -= delta;
/*
* If the last page is partially mapped, then zero out
* the garbage at the end of the page. See comments
* in vnode_pager_setsize() for more details.
*
* XXXJHB: This handles in memory pages, but what about
* a page swapped out to disk?
*/
if ((length & PAGE_MASK) &&
(m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL &&
m->valid != 0) {
int base = (int)length & PAGE_MASK;
int size = PAGE_SIZE - base;
pmap_zero_page_area(m, base, size);
/*
* Update the valid bits to reflect the blocks that
* have been zeroed. Some of these valid bits may
* have already been set.
*/
vm_page_set_valid(m, base, size);
/*
* Round "base" to the next block boundary so that the
* dirty bit for a partially zeroed block is not
* cleared.
*/
base = roundup2(base, DEV_BSIZE);
vm_page_lock_queues();
vm_page_clear_dirty(m, base, PAGE_SIZE - base);
vm_page_unlock_queues();
} else if ((length & PAGE_MASK) &&
__predict_false(object->cache != NULL)) {
vm_page_cache_free(object, OFF_TO_IDX(length),
nobjsize);
}
} else {
/* Attempt to reserve the swap */
delta = ptoa(nobjsize - object->size);
if (!swap_reserve_by_uid(delta, object->uip)) {
VM_OBJECT_UNLOCK(object);
return (ENOMEM);
}
object->charge += delta;
}
shmfd->shm_size = length;
mtx_lock(&shm_timestamp_lock);
vfs_timestamp(&shmfd->shm_ctime);
shmfd->shm_mtime = shmfd->shm_ctime;
mtx_unlock(&shm_timestamp_lock);
object->size = nobjsize;
VM_OBJECT_UNLOCK(object);
return (0);
}
/*
* spec_getpages() - get pages associated with device vnode.
*
* Note that spec_read and spec_write do not use the buffer cache, so we
* must fully implement getpages here.
*/
static int
devfs_spec_getpages(struct vop_getpages_args *ap)
{
vm_offset_t kva;
int error;
int i, pcount, size;
struct buf *bp;
vm_page_t m;
vm_ooffset_t offset;
int toff, nextoff, nread;
struct vnode *vp = ap->a_vp;
int blksiz;
int gotreqpage;
error = 0;
pcount = round_page(ap->a_count) / PAGE_SIZE;
/*
* Calculate the offset of the transfer and do sanity check.
*/
offset = IDX_TO_OFF(ap->a_m[0]->pindex) + ap->a_offset;
/*
* Round up physical size for real devices. We cannot round using
* v_mount's block size data because v_mount has nothing to do with
* the device. i.e. it's usually '/dev'. We need the physical block
* size for the device itself.
*
* We can't use v_rdev->si_mountpoint because it only exists when the
* block device is mounted. However, we can use v_rdev.
*/
if (vn_isdisk(vp, NULL))
blksiz = vp->v_rdev->si_bsize_phys;
else
blksiz = DEV_BSIZE;
size = (ap->a_count + blksiz - 1) & ~(blksiz - 1);
bp = getpbuf_kva(NULL);
kva = (vm_offset_t)bp->b_data;
/*
* Map the pages to be read into the kva.
*/
pmap_qenter(kva, ap->a_m, pcount);
/* Build a minimal buffer header. */
bp->b_cmd = BUF_CMD_READ;
bp->b_bcount = size;
bp->b_resid = 0;
bsetrunningbufspace(bp, size);
bp->b_bio1.bio_offset = offset;
bp->b_bio1.bio_done = devfs_spec_getpages_iodone;
mycpu->gd_cnt.v_vnodein++;
mycpu->gd_cnt.v_vnodepgsin += pcount;
/* Do the input. */
vn_strategy(ap->a_vp, &bp->b_bio1);
crit_enter();
/* We definitely need to be at splbio here. */
while (bp->b_cmd != BUF_CMD_DONE)
tsleep(bp, 0, "spread", 0);
crit_exit();
if (bp->b_flags & B_ERROR) {
if (bp->b_error)
error = bp->b_error;
else
error = EIO;
}
/*
* If EOF is encountered we must zero-extend the result in order
* to ensure that the page does not contain garabge. When no
* error occurs, an early EOF is indicated if b_bcount got truncated.
* b_resid is relative to b_bcount and should be 0, but some devices
* might indicate an EOF with b_resid instead of truncating b_bcount.
*/
nread = bp->b_bcount - bp->b_resid;
if (nread < ap->a_count)
bzero((caddr_t)kva + nread, ap->a_count - nread);
pmap_qremove(kva, pcount);
gotreqpage = 0;
for (i = 0, toff = 0; i < pcount; i++, toff = nextoff) {
nextoff = toff + PAGE_SIZE;
m = ap->a_m[i];
m->flags &= ~PG_ZERO;
/*
* NOTE: vm_page_undirty/clear_dirty etc do not clear the
* pmap modified bit. pmap modified bit should have
* already been cleared.
*/
if (nextoff <= nread) {
m->valid = VM_PAGE_BITS_ALL;
vm_page_undirty(m);
} else if (toff < nread) {
/*
* Since this is a VM request, we have to supply the
* unaligned offset to allow vm_page_set_valid()
* to zero sub-DEV_BSIZE'd portions of the page.
*/
vm_page_set_valid(m, 0, nread - toff);
vm_page_clear_dirty_end_nonincl(m, 0, nread - toff);
} else {
m->valid = 0;
vm_page_undirty(m);
}
if (i != ap->a_reqpage) {
/*
* Just in case someone was asking for this page we
* now tell them that it is ok to use.
*/
if (!error || (m->valid == VM_PAGE_BITS_ALL)) {
if (m->valid) {
if (m->flags & PG_REFERENCED) {
vm_page_activate(m);
} else {
vm_page_deactivate(m);
}
vm_page_wakeup(m);
} else {
vm_page_free(m);
}
} else {
vm_page_free(m);
}
} else if (m->valid) {
gotreqpage = 1;
/*
* Since this is a VM request, we need to make the
* entire page presentable by zeroing invalid sections.
*/
if (m->valid != VM_PAGE_BITS_ALL)
vm_page_zero_invalid(m, FALSE);
}
}
if (!gotreqpage) {
m = ap->a_m[ap->a_reqpage];
devfs_debug(DEVFS_DEBUG_WARNING,
"spec_getpages:(%s) I/O read failure: (error=%d) bp %p vp %p\n",
devtoname(vp->v_rdev), error, bp, bp->b_vp);
devfs_debug(DEVFS_DEBUG_WARNING,
" size: %d, resid: %d, a_count: %d, valid: 0x%x\n",
size, bp->b_resid, ap->a_count, m->valid);
devfs_debug(DEVFS_DEBUG_WARNING,
" nread: %d, reqpage: %d, pindex: %lu, pcount: %d\n",
nread, ap->a_reqpage, (u_long)m->pindex, pcount);
/*
* Free the buffer header back to the swap buffer pool.
*/
relpbuf(bp, NULL);
return VM_PAGER_ERROR;
}
/*
* Free the buffer header back to the swap buffer pool.
*/
relpbuf(bp, NULL);
if (DEVFS_NODE(ap->a_vp))
nanotime(&DEVFS_NODE(ap->a_vp)->mtime);
return VM_PAGER_OK;
}