[patch] hugetlb strict commit accounting - v3

Chen, Kenneth W
2006-03-10T03:14:58Z

hugetlb strict commit accounting for shared mapping - v3

The a region reservation list is implementation as a linked list
hanging off address_space i_data->private_list. It turns out that
clear_inode() was also looking at inode->i_data->private_list and
if not empty, it think inode has dirty buffers and start clearing.
Except it won't go very far before oops-ing. That could happen if
a reservation is made but no actual faulting. hugetlbfs_delete_inode
and hugetlbfs_forget_inode doesn't call truncate_hugepages if there
are no actual page in the page cache, leading to clear_inode to do
bad thing. Change that to always call truncate_hugepages even if
there are no pages in page cache and to let the unreserve code to
clear out the reservation linked list.

Changes since v2:
* fix none empty i_data->private_list before calling clear_inode
* delete VMACCTPG macro

Changes since v1:

* change resv_huge_pages to normal unsigned long
* add proper lock around update/access resv_huge_pages
* resv_huge_pages record future needs of hugetlb pages
* strict commit accounting for shared mapping
* don't allow free_huge_pages to dip below reserved page in sysctl path

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>

--- ./fs/hugetlbfs/inode.c.orig 2006-03-09 15:02:25.558844840 -0800
+++ ./fs/hugetlbfs/inode.c 2006-03-09 19:39:44.786180072 -0800
@@ -56,48 +56,9 @@ static void huge_pagevec_release(struct
pagevec_reinit(pvec);
}

-/*
- * huge_pages_needed tries to determine the number of new huge pages that
- * will be required to fully populate this VMA. This will be equal to
- * the size of the VMA in huge pages minus the number of huge pages
- * (covered by this VMA) that are found in the page cache.
- *
- * Result is in bytes to be compatible with is_hugepage_mem_enough()
- */
-static unsigned long
-huge_pages_needed(struct address_space *mapping, struct vm_area_struct *vma)
-{
- int i;
- struct pagevec pvec;
- unsigned long start = vma->vm_start;
- unsigned long end = vma->vm_end;
- unsigned long hugepages = (end - start) >> HPAGE_SHIFT;
- pgoff_t next = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
- pgoff_t endpg = next + hugepages;
-
- pagevec_init(&pvec, 0);
- while (next < endpg) {
- if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
- break;
- for (i = 0; i < pagevec_count(&pvec); i++) {
- struct page *page = pvec.pages[i];
- if (page->index > next)
- next = page->index;
- if (page->index >= endpg)
- break;
- next++;
- hugepages--;
- }
- huge_pagevec_release(&pvec);
- }
- return hugepages << HPAGE_SHIFT;
-}
-
static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
struct inode *inode = file->f_dentry->d_inode;
- struct address_space *mapping = inode->i_mapping;
- unsigned long bytes;
loff_t len, vma_len;
int ret;

@@ -113,10 +74,6 @@ static int hugetlbfs_file_mmap(struct fi
if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
return -EINVAL;

- bytes = huge_pages_needed(mapping, vma);
- if (!is_hugepage_mem_enough(bytes))
- return -ENOMEM;
-
vma_len = (loff_t)(vma->vm_end - vma->vm_start);

mutex_lock(&inode->i_mutex);
@@ -129,6 +86,10 @@ static int hugetlbfs_file_mmap(struct fi
if (!(vma->vm_flags & VM_WRITE) && len > inode->i_size)
goto out;

+ if (vma->vm_flags & VM_MAYSHARE)
+ if (hugetlb_reserve_pages(inode, vma))
+ goto out;
+
ret = 0;
hugetlb_prefault_arch_hook(vma->vm_mm);
if (inode->i_size < len)
@@ -232,7 +193,7 @@ static void truncate_hugepages(struct ad
const pgoff_t start = lstart >> HPAGE_SHIFT;
struct pagevec pvec;
pgoff_t next;
- int i;
+ int i, freed = 0;

pagevec_init(&pvec, 0);
next = start;
@@ -254,16 +215,17 @@ static void truncate_hugepages(struct ad
truncate_huge_page(page);
unlock_page(page);
hugetlb_put_quota(mapping);
+ freed++;
}
huge_pagevec_release(&pvec);
}
BUG_ON(!lstart && mapping->nrpages);
+ hugetlb_unreserve_pages(mapping->host, start, freed);
}

static void hugetlbfs_delete_inode(struct inode *inode)
{
- if (inode->i_data.nrpages)
- truncate_hugepages(&inode->i_data, 0);
+ truncate_hugepages(&inode->i_data, 0);
clear_inode(inode);
}

@@ -296,8 +258,7 @@ static void hugetlbfs_forget_inode(struc
inode->i_state |= I_FREEING;
inodes_stat.nr_inodes--;
spin_unlock(&inode_lock);
- if (inode->i_data.nrpages)
- truncate_hugepages(&inode->i_data, 0);
+ truncate_hugepages(&inode->i_data, 0);
clear_inode(inode);
destroy_inode(inode);
}
@@ -401,6 +362,7 @@ static struct inode *hugetlbfs_get_inode
inode->i_mapping->a_ops = &hugetlbfs_aops;
inode->i_mapping->backing_dev_info =&hugetlbfs_backing_dev_info;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ INIT_LIST_HEAD(&inode->i_mapping->private_list);
info = HUGETLBFS_I(inode);
mpol_shared_policy_init(&info->policy, MPOL_DEFAULT, NULL);
switch (mode & S_IFMT) {
--- ./include/linux/hugetlb.h.orig 2006-03-09 15:02:25.559821402 -0800
+++ ./include/linux/hugetlb.h 2006-03-09 16:54:55.444504341 -0800
@@ -26,6 +26,8 @@ struct page *alloc_huge_page(struct vm_a
void free_huge_page(struct page *);
int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, int write_access);
+int hugetlb_reserve_pages(struct inode *inode, struct vm_area_struct *vma);
+void hugetlb_unreserve_pages(struct inode *inode, pgoff_t offset, int freed);

extern unsigned long max_huge_pages;
extern const unsigned long hugetlb_zero, hugetlb_infinity;
--- ./mm/hugetlb.c.orig 2006-03-09 15:02:25.559821402 -0800
+++ ./mm/hugetlb.c 2006-03-09 19:46:21.034222092 -0800
@@ -20,7 +20,7 @@
#include <linux/hugetlb.h>

const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
-static unsigned long nr_huge_pages, free_huge_pages;
+static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
unsigned long max_huge_pages;
static struct list_head hugepage_freelists[MAX_NUMNODES];
static unsigned int nr_huge_pages_node[MAX_NUMNODES];
@@ -98,6 +98,12 @@ struct page *alloc_huge_page(struct vm_a
int i;

spin_lock(&hugetlb_lock);
+ if (vma->vm_flags & VM_MAYSHARE)
+ resv_huge_pages--;
+ else if (free_huge_pages <= resv_huge_pages) {
+ spin_unlock(&hugetlb_lock);
+ return NULL;
+ }
page = dequeue_huge_page(vma, addr);
if (!page) {
spin_unlock(&hugetlb_lock);
@@ -199,6 +205,7 @@ static unsigned long set_max_huge_pages(
return nr_huge_pages;

spin_lock(&hugetlb_lock);
+ count = max(count, resv_huge_pages);
try_to_free_low(count);
while (count < nr_huge_pages) {
struct page *page = dequeue_huge_page(NULL, 0);
@@ -225,9 +232,11 @@ int hugetlb_report_meminfo(char *buf)
return sprintf(buf,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
+ "HugePages_Resv: %5lu\n"
"Hugepagesize: %5lu kB\n",
nr_huge_pages,
free_huge_pages,
+ resv_huge_pages,
HPAGE_SIZE/1024);
}

@@ -572,3 +581,165 @@ int follow_hugetlb_page(struct mm_struct

return i;
}
+
+struct file_region {
+ struct list_head link;
+ int from;
+ int to;
+};
+
+static int region_add(struct list_head *head, int f, int t)
+{
+ struct file_region *rg;
+ struct file_region *nrg;
+ struct file_region *trg;
+
+ /* Locate the region we are either in or before. */
+ list_for_each_entry(rg, head, link)
+ if (f <= rg->to)
+ break;
+
+ /* Round our left edge to the current segment if it encloses us. */
+ if (f > rg->from)
+ f = rg->from;
+
+ /* 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;
+ if (rg->from > t)
+ break;
+
+ /* If this area reaches higher then extend our area to
+ * include it completely. If this is not the first area
+ * which we intend to reuse, free it. */
+ if (rg->to > t)
+ t = rg->to;
+ if (rg != nrg) {
+ list_del(&rg->link);
+ kfree(rg);
+ }
+ }
+ nrg->from = f;
+ nrg->to = t;
+ return 0;
+}
+
+static int region_chg(struct list_head *head, int f, int t)
+{
+ struct file_region *rg;
+ struct file_region *nrg;
+ loff_t chg = 0;
+
+ /* Locate the region we are before or in. */
+ list_for_each_entry(rg, head, link)
+ if (f <= rg->to)
+ break;
+
+ /* If we are below the current region then a new region is required.
+ * Subtle, allocate a new region at the position but make it zero
+ * size such that we can guarentee to record the reservation. */
+ if (&rg->link == head || t < rg->from) {
+ nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
+ if (nrg == 0)
+ return -ENOMEM;
+ nrg->from = f;
+ nrg->to = f;
+ INIT_LIST_HEAD(&nrg->link);
+ list_add(&nrg->link, rg->link.prev);
+
+ return t - f;
+ }
+
+ /* Round our left edge to the current segment if it encloses us. */
+ if (f > rg->from)
+ f = rg->from;
+ chg = t - f;
+
+ /* Check for and consume any regions we now overlap with. */
+ list_for_each_entry(rg, rg->link.prev, link) {
+ if (&rg->link == head)
+ break;
+ if (rg->from > t)
+ return chg;
+
+ /* We overlap with this area, if it extends futher than
+ * us then we must extend ourselves. Account for its
+ * existing reservation. */
+ if (rg->to > t) {
+ chg += rg->to - t;
+ t = rg->to;
+ }
+ chg -= rg->to - rg->from;
+ }
+ return chg;
+}
+
+static int region_truncate(struct list_head *head, int end)
+{
+ struct file_region *rg;
+ struct file_region *trg;
+ int chg = 0;
+
+ /* Locate the region we are either in or before. */
+ list_for_each_entry(rg, head, link)
+ if (end <= rg->to)
+ break;
+ if (&rg->link == head)
+ return 0;
+
+ /* If we are in the middle of a region then adjust it. */
+ if (end > rg->from) {
+ chg = rg->to - end;
+ rg->to = end;
+ rg = list_entry(rg->link.next, typeof(*rg), link);
+ }
+
+ /* Drop any remaining regions. */
+ list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
+ if (&rg->link == head)
+ break;
+ chg += rg->to - rg->from;
+ list_del(&rg->link);
+ kfree(rg);
+ }
+ return chg;
+}
+
+static int hugetlb_acct_memory(long delta)
+{
+ int ret = -ENOMEM;
+
+ spin_lock(&hugetlb_lock);
+ if ((delta + resv_huge_pages) <= free_huge_pages) {
+ resv_huge_pages += delta;
+ ret = 0;
+ }
+ spin_unlock(&hugetlb_lock);
+ return ret;
+}
+
+int hugetlb_reserve_pages(struct inode *inode, struct vm_area_struct *vma)
+{
+ int ret, chg;
+ int from = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
+ int to = (vma->vm_pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)) >>
+ (HPAGE_SHIFT - PAGE_SHIFT);
+
+ chg = region_chg(&inode->i_mapping->private_list, from, to);
+ if (chg < 0)
+ return chg;
+ ret = hugetlb_acct_memory(chg);
+ if (ret < 0)
+ return ret;
+ region_add(&inode->i_mapping->private_list, from, to);
+ return 0;
+}
+
+void hugetlb_unreserve_pages(struct inode *inode, pgoff_t offset, int freed)
+{
+ int chg;
+ chg = region_truncate(&inode->i_mapping->private_list, offset);
+ hugetlb_acct_memory(freed - chg);
+}