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When the function blist_fill() was added to the kernel in r107913, the swap

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pager used a different scheme for striping the allocation of swap space
across multiple devices.  And, although blist_fill() was intended to support
fill operations with large counts, the old striping scheme never performed a
fill larger than the stripe size.  Consequently, the misplacement of a
sanity check in blst_meta_fill() went undetected.  Now, moving forward in
time to r118390, a new scheme for striping was introduced that maintained a
blist allocator per device, but as noted in r318995, swapoff_one() was not
fully and correctly converted to the new scheme.  This change completes what
was started in r318995 by fixing the underlying bug in blst_meta_fill() that
stops swapoff_one() from simply performing a single blist_fill() operation.

Reviewed by:	kib
MFC after:	5 days
Differential Revision:	https://reviews.freebsd.org/D11043
This commit is contained in:
Alan Cox 2017-06-06 03:32:17 +00:00
parent e28f9b7d03
commit 03bdd65f18
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=319612
2 changed files with 4 additions and 12 deletions
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5
sys/kern/subr_blist.c
View File

@ -769,6 +769,8 @@ blst_meta_fill(
int next_skip = ((u_int)skip / BLIST_META_RADIX);
int nblks = 0;
if (count > radix)
panic("blist_meta_fill: allocation too large");
if (count == radix || scan->u.bmu_avail == 0) {
/*
* ALL-ALLOCATED special case
@ -800,9 +802,6 @@ blst_meta_fill(
radix /= BLIST_META_RADIX;
}
if (count > radix)
panic("blist_meta_fill: allocation too large");
i = (allocBlk - blk) / radix;
blk += i * radix;
i = i * next_skip + 1;

11
sys/vm/swap_pager.c
View File

@ -2271,7 +2271,7 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap)
static int
swapoff_one(struct swdevt *sp, struct ucred *cred)
{
u_long nblks, dvbase;
u_long nblks;
#ifdef MAC
int error;
#endif
@ -2300,14 +2300,7 @@ swapoff_one(struct swdevt *sp, struct ucred *cred)
*/
mtx_lock(&sw_dev_mtx);
sp->sw_flags |= SW_CLOSING;
for (dvbase = 0; dvbase < nblks; dvbase += BLIST_BMAP_RADIX) {
/*
* blist_fill() cannot allocate more than BLIST_BMAP_RADIX
* blocks per call.
*/
swap_pager_avail -= blist_fill(sp->sw_blist,
dvbase, ulmin(nblks - dvbase, BLIST_BMAP_RADIX));
}
swap_pager_avail -= blist_fill(sp->sw_blist, 0, nblks);
swap_total -= (vm_ooffset_t)nblks * PAGE_SIZE;
mtx_unlock(&sw_dev_mtx);