In swp_pager_meta_build(), handle a race with other thread allocating
swapblk for our index while we dropped the object lock. Noted by: jeff Reviewed by: alc, markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week
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badd2a3546
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eed99cb81b
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=323224
@ -1726,7 +1726,7 @@ static void
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swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
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{
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static volatile int swblk_zone_exhausted, swpctrie_zone_exhausted;
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struct swblk *sb;
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struct swblk *sb, *sb1;
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vm_pindex_t modpi, rdpi;
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int error, i;
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@ -1776,6 +1776,15 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
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} else
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VM_WAIT;
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VM_OBJECT_WLOCK(object);
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sb = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
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rdpi);
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if (sb != NULL)
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/*
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* Somebody swapped out a nearby page,
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* allocating swblk at the rdpi index,
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* while we dropped the object lock.
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*/
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goto allocated;
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}
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for (;;) {
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error = SWAP_PCTRIE_INSERT(
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@ -1797,8 +1806,16 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
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} else
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VM_WAIT;
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VM_OBJECT_WLOCK(object);
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sb1 = SWAP_PCTRIE_LOOKUP(&object->un_pager.swp.swp_blks,
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rdpi);
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if (sb1 != NULL) {
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uma_zfree(swblk_zone, sb);
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sb = sb1;
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goto allocated;
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}
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}
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}
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allocated:
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MPASS(sb->p == rdpi);
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modpi = pindex % SWAP_META_PAGES;
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