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Respect the caller's hints when performing swap readahead.

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The pager getpages interface allows the caller to bound the number of
readahead and readbehind pages, and vm_fault_hold() makes use of this
feature. These bounds were ignored after r305056, causing the swap pager
to potentially page in more than the specified number of pages.

Reported and reviewed by:	alc
X-MFC with:	r305056
This commit is contained in:
Mark Johnston 2016-09-04 00:25:49 +00:00
parent 664a749708
commit dd9cb6da0b
1 changed files with 5 additions and 4 deletions
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9
sys/vm/swap_pager.c
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@ -1086,7 +1086,7 @@ swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
vm_page_t mpred, msucc, p;
vm_pindex_t pindex;
daddr_t blk;
int i, j, reqcount, shift;
int i, j, maxahead, maxbehind, reqcount, shift;
reqcount = count;
@ -1094,7 +1094,7 @@ swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
bp = getpbuf(&nsw_rcount);
VM_OBJECT_WLOCK(object);
if (!swap_pager_haspage(object, m[0]->pindex, rbehind, rahead)) {
if (!swap_pager_haspage(object, m[0]->pindex, &maxbehind, &maxahead)) {
relpbuf(bp, &nsw_rcount);
return (VM_PAGER_FAIL);
}
@ -1103,15 +1103,16 @@ swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
* Clip the readahead and readbehind ranges to exclude resident pages.
*/
if (rahead != NULL) {
KASSERT(reqcount - 1 <= *rahead,
KASSERT(reqcount - 1 <= maxahead,
("page count %d extends beyond swap block", reqcount));
*rahead -= reqcount - 1;
*rahead = imin(*rahead, maxahead - (reqcount - 1));
pindex = m[reqcount - 1]->pindex;
msucc = TAILQ_NEXT(m[reqcount - 1], listq);
if (msucc != NULL && msucc->pindex - pindex - 1 < *rahead)
*rahead = msucc->pindex - pindex - 1;
}
if (rbehind != NULL) {
*rbehind = imin(*rbehind, maxbehind);
pindex = m[0]->pindex;
mpred = TAILQ_PREV(m[0], pglist, listq);
if (mpred != NULL && pindex - mpred->pindex - 1 < *rbehind)