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Fix a boundary case error in vm_reserv_alloc_contig(): If a reservation

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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
This commit is contained in:
Alan Cox 2014-09-10 05:52:30 +00:00
parent b3f7f76b8a
commit 64f096eeb2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=271351
1 changed files with 23 additions and 9 deletions
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32
sys/vm/vm_reserv.c
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@ -364,7 +364,7 @@ vm_reserv_populate(vm_reserv_t rv, int index)
/*
* 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 object, vm_pindex_t pindex, u_long npages,
/*
* 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 object, vm_pindex_t pindex, u_long npages,
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 object, vm_pindex_t pindex, u_long npages,
}
/*
* 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 object, vm_pindex_t pindex, u_long npages,
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);
/*