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hugetlb: disable region_add file_region coalescing

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A follow up patch in this series adds hugetlb cgroup uncharge info the
file_region entries in resv->regions.  The cgroup uncharge info may differ
for different regions, so they can no longer be coalesced at region_add
time.  So, disable region coalescing in region_add in this patch.

Behavior change:

Say a resv_map exists like this [0->1], [2->3], and [5->6].

Then a region_chg/add call comes in region_chg/add(f=0, t=5).

Old code would generate resv->regions: [0->5], [5->6].
New code would generate resv->regions: [0->1], [1->2], [2->3], [3->5],
[5->6].

Special care needs to be taken to handle the resv->adds_in_progress
variable correctly.  In the past, only 1 region would be added for every
region_chg and region_add call.  But now, each call may add multiple
regions, so we can no longer increment adds_in_progress by 1 in
region_chg, or decrement adds_in_progress by 1 after region_add or
region_abort.  Instead, region_chg calls add_reservation_in_range() to
count the number of regions needed and allocates those, and that info is
passed to region_add and region_abort to decrement adds_in_progress
correctly.

We've also modified the assumption that region_add after region_chg never
fails.  region_chg now pre-allocates at least 1 region for region_add.  If
region_add needs more regions than region_chg has allocated for it, then
it may fail.

[almasrymina@google.com: fix file_region entry allocations]
  Link: http://lkml.kernel.org/r/20200219012736.20363-1-almasrymina@google.com
Signed-off-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: http://lkml.kernel.org/r/20200211213128.73302-4-almasrymina@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mina Almasry 2020-04-01 21:11:25 -07:00 committed by Linus Torvalds
parent e9fe92ae0c
commit 0db9d74ed8
1 changed files with 227 additions and 107 deletions
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334
mm/hugetlb.c
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@ -245,107 +245,217 @@ struct file_region {
long to;
};
/* Helper that removes a struct file_region from the resv_map cache and returns
* it for use.
*/
static struct file_region *
get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
{
struct file_region *nrg = NULL;
VM_BUG_ON(resv->region_cache_count <= 0);
resv->region_cache_count--;
nrg = list_first_entry(&resv->region_cache, struct file_region, link);
VM_BUG_ON(!nrg);
list_del(&nrg->link);
nrg->from = from;
nrg->to = to;
return nrg;
}
/* Must be called with resv->lock held. Calling this with count_only == true
* will count the number of pages to be added but will not modify the linked
* list.
* list. If regions_needed != NULL and count_only == true, then regions_needed
* will indicate the number of file_regions needed in the cache to carry out to
* add the regions for this range.
*/
static long add_reservation_in_range(struct resv_map *resv, long f, long t,
bool count_only)
long *regions_needed, bool count_only)
{
long chg = 0;
long add = 0;
struct list_head *head = &resv->regions;
long last_accounted_offset = f;
struct file_region *rg = NULL, *trg = NULL, *nrg = NULL;
/* Locate the region we are before or in. */
list_for_each_entry(rg, head, link)
if (f <= rg->to)
break;
if (regions_needed)
*regions_needed = 0;
/* Round our left edge to the current segment if it encloses us. */
if (f > rg->from)
f = rg->from;
/* In this loop, we essentially handle an entry for the range
* [last_accounted_offset, rg->from), at every iteration, with some
* bounds checking.
*/
list_for_each_entry_safe(rg, trg, head, link) {
/* Skip irrelevant regions that start before our range. */
if (rg->from < f) {
/* If this region ends after the last accounted offset,
* then we need to update last_accounted_offset.
*/
if (rg->to > last_accounted_offset)
last_accounted_offset = rg->to;
continue;
}
chg = t - f;
/* Check for and consume any regions we now overlap with. */
nrg = rg;
list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
if (&rg->link == head)
break;
/* When we find a region that starts beyond our range, we've
* finished.
*/
if (rg->from > t)
break;
/* We overlap with this area, if it extends further than
* us then we must extend ourselves. Account for its
* existing reservation.
/* Add an entry for last_accounted_offset -> rg->from, and
* update last_accounted_offset.
*/
if (rg->to > t) {
chg += rg->to - t;
t = rg->to;
if (rg->from > last_accounted_offset) {
add += rg->from - last_accounted_offset;
if (!count_only) {
nrg = get_file_region_entry_from_cache(
resv, last_accounted_offset, rg->from);
list_add(&nrg->link, rg->link.prev);
} else if (regions_needed)
*regions_needed += 1;
}
chg -= rg->to - rg->from;
if (!count_only && rg != nrg) {
last_accounted_offset = rg->to;
}
/* Handle the case where our range extends beyond
* last_accounted_offset.
*/
if (last_accounted_offset < t) {
add += t - last_accounted_offset;
if (!count_only) {
nrg = get_file_region_entry_from_cache(
resv, last_accounted_offset, t);
list_add(&nrg->link, rg->link.prev);
} else if (regions_needed)
*regions_needed += 1;
}
VM_BUG_ON(add < 0);
return add;
}
/* Must be called with resv->lock acquired. Will drop lock to allocate entries.
*/
static int allocate_file_region_entries(struct resv_map *resv,
int regions_needed)
__must_hold(&resv->lock)
{
struct list_head allocated_regions;
int to_allocate = 0, i = 0;
struct file_region *trg = NULL, *rg = NULL;
VM_BUG_ON(regions_needed < 0);
INIT_LIST_HEAD(&allocated_regions);
/*
* Check for sufficient descriptors in the cache to accommodate
* the number of in progress add operations plus regions_needed.
*
* This is a while loop because when we drop the lock, some other call
* to region_add or region_del may have consumed some region_entries,
* so we keep looping here until we finally have enough entries for
* (adds_in_progress + regions_needed).
*/
while (resv->region_cache_count <
(resv->adds_in_progress + regions_needed)) {
to_allocate = resv->adds_in_progress + regions_needed -
resv->region_cache_count;
/* At this point, we should have enough entries in the cache
* for all the existings adds_in_progress. We should only be
* needing to allocate for regions_needed.
*/
VM_BUG_ON(resv->region_cache_count < resv->adds_in_progress);
spin_unlock(&resv->lock);
for (i = 0; i < to_allocate; i++) {
trg = kmalloc(sizeof(*trg), GFP_KERNEL);
if (!trg)
goto out_of_memory;
list_add(&trg->link, &allocated_regions);
}
spin_lock(&resv->lock);
list_for_each_entry_safe(rg, trg, &allocated_regions, link) {
list_del(&rg->link);
kfree(rg);
list_add(&rg->link, &resv->region_cache);
resv->region_cache_count++;
}
}
if (!count_only) {
nrg->from = f;
nrg->to = t;
}
return 0;
return chg;
out_of_memory:
list_for_each_entry_safe(rg, trg, &allocated_regions, link) {
list_del(&rg->link);
kfree(rg);
}
return -ENOMEM;
}
/*
* Add the huge page range represented by [f, t) to the reserve
* map. Existing regions will be expanded to accommodate the specified
* range, or a region will be taken from the cache. Sufficient regions
* must exist in the cache due to the previous call to region_chg with
* the same range.
* map. Regions will be taken from the cache to fill in this range.
* Sufficient regions should exist in the cache due to the previous
* call to region_chg with the same range, but in some cases the cache will not
* have sufficient entries due to races with other code doing region_add or
* region_del. The extra needed entries will be allocated.
*
* Return the number of new huge pages added to the map. This
* number is greater than or equal to zero.
* regions_needed is the out value provided by a previous call to region_chg.
*
* Return the number of new huge pages added to the map. This number is greater
* than or equal to zero. If file_region entries needed to be allocated for
* this operation and we were not able to allocate, it ruturns -ENOMEM.
* region_add of regions of length 1 never allocate file_regions and cannot
* fail; region_chg will always allocate at least 1 entry and a region_add for
* 1 page will only require at most 1 entry.
*/
static long region_add(struct resv_map *resv, long f, long t)
static long region_add(struct resv_map *resv, long f, long t,
long in_regions_needed)
{
struct list_head *head = &resv->regions;
struct file_region *rg, *nrg;
long add = 0;
long add = 0, actual_regions_needed = 0;
spin_lock(&resv->lock);
/* Locate the region we are either in or before. */
list_for_each_entry(rg, head, link)
if (f <= rg->to)
break;
retry:
/* Count how many regions are actually needed to execute this add. */
add_reservation_in_range(resv, f, t, &actual_regions_needed, true);
/*
* If no region exists which can be expanded to include the
* specified range, pull a region descriptor from the cache
* and use it for this range.
* Check for sufficient descriptors in the cache to accommodate
* this add operation. Note that actual_regions_needed may be greater
* than in_regions_needed, as the resv_map may have been modified since
* the region_chg call. In this case, we need to make sure that we
* allocate extra entries, such that we have enough for all the
* existing adds_in_progress, plus the excess needed for this
* operation.
*/
if (&rg->link == head || t < rg->from) {
VM_BUG_ON(resv->region_cache_count <= 0);
if (actual_regions_needed > in_regions_needed &&
resv->region_cache_count <
resv->adds_in_progress +
(actual_regions_needed - in_regions_needed)) {
/* region_add operation of range 1 should never need to
* allocate file_region entries.
*/
VM_BUG_ON(t - f <= 1);
resv->region_cache_count--;
nrg = list_first_entry(&resv->region_cache, struct file_region,
link);
list_del(&nrg->link);
if (allocate_file_region_entries(
resv, actual_regions_needed - in_regions_needed)) {
return -ENOMEM;
}
nrg->from = f;
nrg->to = t;
list_add(&nrg->link, rg->link.prev);
add += t - f;
goto out_locked;
goto retry;
}
add = add_reservation_in_range(resv, f, t, false);
add = add_reservation_in_range(resv, f, t, NULL, false);
resv->adds_in_progress -= in_regions_needed;
out_locked:
resv->adds_in_progress--;
spin_unlock(&resv->lock);
VM_BUG_ON(add < 0);
return add;
@ -358,46 +468,36 @@ out_locked:
* call to region_add that will actually modify the reserve
* map to add the specified range [f, t). region_chg does
* not change the number of huge pages represented by the
* map. A new file_region structure is added to the cache
* as a placeholder, so that the subsequent region_add
* call will have all the regions it needs and will not fail.
* map. A number of new file_region structures is added to the cache as a
* placeholder, for the subsequent region_add call to use. At least 1
* file_region structure is added.
*
* out_regions_needed is the number of regions added to the
* resv->adds_in_progress. This value needs to be provided to a follow up call
* to region_add or region_abort for proper accounting.
*
* Returns the number of huge pages that need to be added to the existing
* reservation map for the range [f, t). This number is greater or equal to
* zero. -ENOMEM is returned if a new file_region structure or cache entry
* is needed and can not be allocated.
*/
static long region_chg(struct resv_map *resv, long f, long t)
static long region_chg(struct resv_map *resv, long f, long t,
long *out_regions_needed)
{
long chg = 0;
spin_lock(&resv->lock);
retry_locked:
resv->adds_in_progress++;
/*
* Check for sufficient descriptors in the cache to accommodate
* the number of in progress add operations.
*/
if (resv->adds_in_progress > resv->region_cache_count) {
struct file_region *trg;
/* Count how many hugepages in this range are NOT respresented. */
chg = add_reservation_in_range(resv, f, t, out_regions_needed, true);
VM_BUG_ON(resv->adds_in_progress - resv->region_cache_count > 1);
/* Must drop lock to allocate a new descriptor. */
resv->adds_in_progress--;
spin_unlock(&resv->lock);
if (*out_regions_needed == 0)
*out_regions_needed = 1;
trg = kmalloc(sizeof(*trg), GFP_KERNEL);
if (!trg)
return -ENOMEM;
if (allocate_file_region_entries(resv, *out_regions_needed))
return -ENOMEM;
spin_lock(&resv->lock);
list_add(&trg->link, &resv->region_cache);
resv->region_cache_count++;
goto retry_locked;
}
chg = add_reservation_in_range(resv, f, t, true);
resv->adds_in_progress += *out_regions_needed;
spin_unlock(&resv->lock);
return chg;
@ -408,17 +508,20 @@ retry_locked:
* of the resv_map keeps track of the operations in progress between
* calls to region_chg and region_add. Operations are sometimes
* aborted after the call to region_chg. In such cases, region_abort
* is called to decrement the adds_in_progress counter.
* is called to decrement the adds_in_progress counter. regions_needed
* is the value returned by the region_chg call, it is used to decrement
* the adds_in_progress counter.
*
* NOTE: The range arguments [f, t) are not needed or used in this
* routine. They are kept to make reading the calling code easier as
* arguments will match the associated region_chg call.
*/
static void region_abort(struct resv_map *resv, long f, long t)
static void region_abort(struct resv_map *resv, long f, long t,
long regions_needed)
{
spin_lock(&resv->lock);
VM_BUG_ON(!resv->region_cache_count);
resv->adds_in_progress--;
resv->adds_in_progress -= regions_needed;
spin_unlock(&resv->lock);
}
@ -2004,6 +2107,7 @@ static long __vma_reservation_common(struct hstate *h,
struct resv_map *resv;
pgoff_t idx;
long ret;
long dummy_out_regions_needed;
resv = vma_resv_map(vma);
if (!resv)
@ -2012,20 +2116,29 @@ static long __vma_reservation_common(struct hstate *h,
idx = vma_hugecache_offset(h, vma, addr);
switch (mode) {
case VMA_NEEDS_RESV:
ret = region_chg(resv, idx, idx + 1);
ret = region_chg(resv, idx, idx + 1, &dummy_out_regions_needed);
/* We assume that vma_reservation_* routines always operate on
* 1 page, and that adding to resv map a 1 page entry can only
* ever require 1 region.
*/
VM_BUG_ON(dummy_out_regions_needed != 1);
break;
case VMA_COMMIT_RESV:
ret = region_add(resv, idx, idx + 1);
ret = region_add(resv, idx, idx + 1, 1);
/* region_add calls of range 1 should never fail. */
VM_BUG_ON(ret < 0);
break;
case VMA_END_RESV:
region_abort(resv, idx, idx + 1);
region_abort(resv, idx, idx + 1, 1);
ret = 0;
break;
case VMA_ADD_RESV:
if (vma->vm_flags & VM_MAYSHARE)
ret = region_add(resv, idx, idx + 1);
else {
region_abort(resv, idx, idx + 1);
if (vma->vm_flags & VM_MAYSHARE) {
ret = region_add(resv, idx, idx + 1, 1);
/* region_add calls of range 1 should never fail. */
VM_BUG_ON(ret < 0);
} else {
region_abort(resv, idx, idx + 1, 1);
ret = region_del(resv, idx, idx + 1);
}
break;
@ -4713,12 +4826,12 @@ int hugetlb_reserve_pages(struct inode *inode,
struct vm_area_struct *vma,
vm_flags_t vm_flags)
{
long ret, chg;
long ret, chg, add = -1;
struct hstate *h = hstate_inode(inode);
struct hugepage_subpool *spool = subpool_inode(inode);
struct resv_map *resv_map;
struct hugetlb_cgroup *h_cg;
long gbl_reserve;
long gbl_reserve, regions_needed = 0;
/* This should never happen */
if (from > to) {
@ -4748,7 +4861,7 @@ int hugetlb_reserve_pages(struct inode *inode,
*/
resv_map = inode_resv_map(inode);
chg = region_chg(resv_map, from, to);
chg = region_chg(resv_map, from, to, &regions_needed);
} else {
/* Private mapping. */
@ -4814,9 +4927,14 @@ int hugetlb_reserve_pages(struct inode *inode,
* else has to be done for private mappings here
*/
if (!vma || vma->vm_flags & VM_MAYSHARE) {
long add = region_add(resv_map, from, to);
add = region_add(resv_map, from, to, regions_needed);
if (unlikely(chg > add)) {
if (unlikely(add < 0)) {
hugetlb_acct_memory(h, -gbl_reserve);
/* put back original number of pages, chg */
(void)hugepage_subpool_put_pages(spool, chg);
goto out_err;
} else if (unlikely(chg > add)) {
/*
* pages in this range were added to the reserve
* map between region_chg and region_add. This
@ -4834,9 +4952,11 @@ int hugetlb_reserve_pages(struct inode *inode,
return 0;
out_err:
if (!vma || vma->vm_flags & VM_MAYSHARE)
/* Don't call region_abort if region_chg failed */
if (chg >= 0)
region_abort(resv_map, from, to);
/* Only call region_abort if the region_chg succeeded but the
* region_add failed or didn't run.
*/
if (chg >= 0 && add < 0)
region_abort(resv_map, from, to, regions_needed);
if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
kref_put(&resv_map->refs, resv_map_release);
return ret;