Date: Wed, 10 Sep 2014 05:52:30 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r271351 - head/sys/vm Message-ID: <201409100552.s8A5qUjC039448@svn.freebsd.org>
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Author: alc Date: Wed Sep 10 05:52:30 2014 New Revision: 271351 URL: http://svnweb.freebsd.org/changeset/base/271351 Log: Fix a boundary case error in vm_reserv_alloc_contig(): If a reservation isn't being allocated for the last of the requested pages, because a reservation won't fit in the gap between allocated pages, then the reservation structure shouldn't be initialized. While I'm here, improve the nearby comments. Reported by: jeff, pho MFC after: 1 week Sponsored by: EMC / Isilon Storage Division Modified: head/sys/vm/vm_reserv.c Modified: head/sys/vm/vm_reserv.c ============================================================================== --- head/sys/vm/vm_reserv.c Wed Sep 10 05:44:15 2014 (r271350) +++ head/sys/vm/vm_reserv.c Wed Sep 10 05:52:30 2014 (r271351) @@ -364,7 +364,7 @@ vm_reserv_populate(vm_reserv_t rv, int i /* * Allocates a contiguous set of physical pages of the given size "npages" - * from an existing or newly-created reservation. All of the physical pages + * from existing or newly created reservations. All of the physical pages * must be at or above the given physical address "low" and below the given * physical address "high". The given value "alignment" determines the * alignment of the first physical page in the set. If the given value @@ -436,8 +436,8 @@ vm_reserv_alloc_contig(vm_object_t objec /* * Could at least one reservation fit between the first index to the - * left that can be used and the first index to the right that cannot - * be used? + * left that can be used ("leftcap") and the first index to the right + * that cannot be used ("rightcap")? */ first = pindex - VM_RESERV_INDEX(object, pindex); if (mpred != NULL) { @@ -459,6 +459,13 @@ vm_reserv_alloc_contig(vm_object_t objec if (first + maxpages > rightcap) { if (maxpages == VM_LEVEL_0_NPAGES) return (NULL); + + /* + * At least one reservation will fit between "leftcap" + * and "rightcap". However, a reservation for the + * last of the requested pages will not fit. Reduce + * the size of the upcoming allocation accordingly. + */ allocpages = minpages; } } @@ -482,16 +489,23 @@ vm_reserv_alloc_contig(vm_object_t objec } /* - * Allocate and populate the new reservations. The alignment and - * boundary specified for this allocation may be different from the - * alignment and boundary specified for the requested pages. For - * instance, the specified index may not be the first page within the - * first new reservation. + * Allocate the physical pages. The alignment and boundary specified + * for this allocation may be different from the alignment and + * boundary specified for the requested pages. For instance, the + * specified index may not be the first page within the first new + * reservation. */ m = vm_phys_alloc_contig(allocpages, low, high, ulmax(alignment, VM_LEVEL_0_SIZE), boundary > VM_LEVEL_0_SIZE ? boundary : 0); if (m == NULL) return (NULL); + + /* + * The allocated physical pages always begin at a reservation + * boundary, but they do not always end at a reservation boundary. + * Initialize every reservation that is completely covered by the + * allocated physical pages. + */ m_ret = NULL; index = VM_RESERV_INDEX(object, pindex); do { @@ -525,7 +539,7 @@ vm_reserv_alloc_contig(vm_object_t objec m += VM_LEVEL_0_NPAGES; first += VM_LEVEL_0_NPAGES; allocpages -= VM_LEVEL_0_NPAGES; - } while (allocpages > 0); + } while (allocpages >= VM_LEVEL_0_NPAGES); return (m_ret); /*
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