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Fix handling of subpage BIO_WRITE and BIO_DELETE requests on swap MDs.

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Such requests would previously mark the entire page as valid, which was
incorrect since nothing guaranteed that the page's contents had been
initialized. This change also modifies subpage BIO_DELETEs so that the
entire page is marked dirty, rather than only a subrange. There is no
benefit to creating partially dirty swap pages.

Reviewed by:	alc, kib (previous version)
MFC after:	3 days
This commit is contained in:
Mark Johnston 2017-06-14 03:45:26 +00:00
parent 2d1353a21d
commit cc2fe2b0fb
1 changed files with 40 additions and 22 deletions
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62
sys/dev/md/md.c
View File

@ -972,6 +972,16 @@ unmapped_step:
return (error);
}
static void
md_swap_page_free(vm_page_t m)
{
vm_page_xunbusy(m);
vm_page_lock(m);
vm_page_free(m);
vm_page_unlock(m);
}
static int
mdstart_swap(struct md_s *sc, struct bio *bp)
{
@ -1044,15 +1054,17 @@ mdstart_swap(struct md_s *sc, struct bio *bp)
cpu_flush_dcache(p, len);
}
} else if (bp->bio_cmd == BIO_WRITE) {
if (len != PAGE_SIZE && m->valid != VM_PAGE_BITS_ALL)
if (len == PAGE_SIZE || m->valid == VM_PAGE_BITS_ALL)
rv = VM_PAGER_OK;
else
rv = vm_pager_get_pages(sc->object, &m, 1,
NULL, NULL);
else
rv = VM_PAGER_OK;
if (rv == VM_PAGER_ERROR) {
vm_page_xunbusy(m);
break;
}
} else if (rv == VM_PAGER_FAIL)
pmap_zero_page(m);
if ((bp->bio_flags & BIO_UNMAPPED) != 0) {
pmap_copy_pages(bp->bio_ma, ma_offs, &m,
offs, len);
@ -1062,34 +1074,40 @@ mdstart_swap(struct md_s *sc, struct bio *bp)
} else {
physcopyin(p, VM_PAGE_TO_PHYS(m) + offs, len);
}
m->valid = VM_PAGE_BITS_ALL;
vm_page_dirty(m);
vm_pager_page_unswapped(m);
} else if (bp->bio_cmd == BIO_DELETE) {
if (len != PAGE_SIZE && m->valid != VM_PAGE_BITS_ALL)
if (len == PAGE_SIZE || m->valid == VM_PAGE_BITS_ALL)
rv = VM_PAGER_OK;
else
rv = vm_pager_get_pages(sc->object, &m, 1,
NULL, NULL);
else
rv = VM_PAGER_OK;
if (rv == VM_PAGER_ERROR) {
vm_page_xunbusy(m);
break;
}
if (len != PAGE_SIZE) {
pmap_zero_page_area(m, offs, len);
vm_page_clear_dirty(m, offs, len);
m->valid = VM_PAGE_BITS_ALL;
} else
} else if (rv == VM_PAGER_FAIL) {
md_swap_page_free(m);
m = NULL;
} else {
/* Page is valid. */
if (len != PAGE_SIZE) {
pmap_zero_page_area(m, offs, len);
vm_page_dirty(m);
}
vm_pager_page_unswapped(m);
if (len == PAGE_SIZE) {
md_swap_page_free(m);
m = NULL;
}
}
}
vm_page_xunbusy(m);
vm_page_lock(m);
if (bp->bio_cmd == BIO_DELETE && len == PAGE_SIZE)
vm_page_free(m);
else
if (m != NULL) {
vm_page_xunbusy(m);
vm_page_lock(m);
vm_page_activate(m);
vm_page_unlock(m);
if (bp->bio_cmd == BIO_WRITE) {
vm_page_dirty(m);
vm_pager_page_unswapped(m);
vm_page_unlock(m);
}
/* Actions on further pages start at offset 0 */