[PATCH V3 0/4] hugetlbfs: add min_size filesystem mount option

[PATCH V3 0/4] hugetlbfs: add min_size filesystem mount option

[Mike Kravetz]

hugetlbfs allocates huge pages from the global pool as needed.  Even if
the global pool contains a sufficient number pages for the filesystem
size at mount time, those global pages could be grabbed for some other
use.  As a result, filesystem huge page allocations may fail due to lack
of pages.

Applications such as a database want to use huge pages for performance
reasons.  hugetlbfs filesystem semantics with ownership and modes work
well to manage access to a pool of huge pages.  However, the application
would like some reasonable assurance that allocations will not fail due
to a lack of huge pages.  At application startup time, the application
would like to configure itself to use a specific number of huge pages.
Before starting, the application can check to make sure that enough huge
pages exist in the system global pools.  However, there are no guarantees
that those pages will be available when needed by the application.  What
the application wants is exclusive use of a subset of huge pages.

Add a new hugetlbfs mount option 'min_size=<value>' to indicate that
the specified number of pages will be available for use by the filesystem.
At mount time, this number of huge pages will be reserved for exclusive
use of the filesystem.  If there is not a sufficient number of free pages,
the mount will fail.  As pages are allocated to and freeed from the
filesystem, the number of reserved pages is adjusted so that the specified
minimum is maintained.

V3:
  Struct init and comment cleanup as suggested by Andrew Morton
  Cleaned up size option argument parsing to hopefully be more clear
  Fixed kbuild warning introduced in V2
  Made documentation more explicit and added descriptions for 'existing'
  pagesize options and ability to specify size as a percent
V2:
  Added ability to specify minimum size. Suggsted by David Rientjes
V1:
  Comments from RFC addressed/incorporated

Mike Kravetz (4):
  hugetlbfs: add minimum size tracking fields to subpool structure
  hugetlbfs: add minimum size accounting to subpools
  hugetlbfs: accept subpool min_size mount option and setup accordingly
  hugetlbfs: document min_size mount option and cleanup

 Documentation/vm/hugetlbpage.txt |  31 +++++---
 fs/hugetlbfs/inode.c             |  90 ++++++++++++++++++-----
 include/linux/hugetlb.h          |  11 ++-
 mm/hugetlb.c                     | 151 +++++++++++++++++++++++++++++++--------
 4 files changed, 224 insertions(+), 59 deletions(-)

-- 
2.1.0

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[PATCH V3 1/4] hugetlbfs: add minimum size tracking fields to subpool structure

[Mike Kravetz]

Add a field to the subpool structure to indicate the minimimum
number of huge pages to always be used by this subpool.  This
minimum count includes allocated pages as well as reserved pages.
If the minimum number of pages for the subpool have not been
allocated, pages are reserved up to this minimum.  An additional
field (rsv_hpages) is used to track the number of pages reserved
to meet this minimum size.  The hstate pointer in the subpool
is convenient to have when reserving and unreserving the pages.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb.h | 8 +++++++-
 mm/hugetlb.c            | 3 +--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 431b7fc..2ec06a1 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -22,7 +22,13 @@ struct mmu_gather;
 struct hugepage_subpool {
 	spinlock_t lock;
 	long count;
-	long max_hpages, used_hpages;
+	long max_hpages;	/* Maximum huge pages or -1 if no maximum. */
+	long used_hpages;	/* Used count against maximum, includes */
+				/* both alloced and reserved pages. */
+	struct hstate *hstate;
+	long min_hpages;	/* Minimum huge pages or -1 if no minimum. */
+	long rsv_hpages;	/* Pages reserved against global pool to */
+				/* sasitfy minimum size. */
 };
 
 struct resv_map {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 85032de..0b4a01c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -77,14 +77,13 @@ struct hugepage_subpool *hugepage_new_subpool(long nr_blocks)
 {
 	struct hugepage_subpool *spool;
 
-	spool = kmalloc(sizeof(*spool), GFP_KERNEL);
+	spool = kzalloc(sizeof(*spool), GFP_KERNEL);
 	if (!spool)
 		return NULL;
 
 	spin_lock_init(&spool->lock);
 	spool->count = 1;
 	spool->max_hpages = nr_blocks;
-	spool->used_hpages = 0;
 
 	return spool;
 }
-- 
2.1.0

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[PATCH V3 2/4] hugetlbfs: add minimum size accounting to subpools

[Mike Kravetz]

The same routines that perform subpool maximum size accounting
hugepage_subpool_get/put_pages() are modified to also perform
minimum size accounting.  When a delta value is passed to these
routines, calculate how global reservations must be adjusted
to maintain the subpool minimum size.  The routines now return
this global reserve count adjustment.  This global reserve count
adjustment is then passed to the global accounting routine
hugetlb_acct_memory().

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 100 insertions(+), 23 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0b4a01c..28a15c3 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -96,36 +96,89 @@ void hugepage_put_subpool(struct hugepage_subpool *spool)
 	unlock_or_release_subpool(spool);
 }
 
-static int hugepage_subpool_get_pages(struct hugepage_subpool *spool,
+/*
+ * Subpool accounting for allocating and reserving pages.
+ * Return -ENOMEM if there are not enough resources to satisfy the
+ * the request.  Otherwise, return the number of pages by which the
+ * global pools must be adjusted (upward).  The returned value may
+ * only be different than the passed value (delta) in the case where
+ * a subpool minimum size must be manitained.
+ */
+static long hugepage_subpool_get_pages(struct hugepage_subpool *spool,
 				      long delta)
 {
-	int ret = 0;
+	long ret = delta;
 
 	if (!spool)
-		return 0;
+		return ret;
 
 	spin_lock(&spool->lock);
-	if ((spool->used_hpages + delta) <= spool->max_hpages) {
-		spool->used_hpages += delta;
-	} else {
-		ret = -ENOMEM;
+
+	if (spool->max_hpages != -1) {		/* maximum size accounting */
+		if ((spool->used_hpages + delta) <= spool->max_hpages)
+			spool->used_hpages += delta;
+		else {
+			ret = -ENOMEM;
+			goto unlock_ret;
+		}
 	}
-	spin_unlock(&spool->lock);
 
+	if (spool->min_hpages != -1) {		/* minimum size accounting */
+		if (delta > spool->rsv_hpages) {
+			/*
+			 * Asking for more reserves than those already taken on
+			 * behalf of subpool.  Return difference.
+			 */
+			ret = delta - spool->rsv_hpages;
+			spool->rsv_hpages = 0;
+		} else {
+			ret = 0;	/* reserves already accounted for */
+			spool->rsv_hpages -= delta;
+		}
+	}
+
+unlock_ret:
+	spin_unlock(&spool->lock);
 	return ret;
 }
 
-static void hugepage_subpool_put_pages(struct hugepage_subpool *spool,
+/*
+ * Subpool accounting for freeing and unreserving pages.
+ * Return the number of global page reservations that must be dropped.
+ * The return value may only be different than the passed value (delta)
+ * in the case where a subpool minimum size must be maintained.
+ */
+static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
 				       long delta)
 {
+	long ret = delta;
+
 	if (!spool)
-		return;
+		return delta;
 
 	spin_lock(&spool->lock);
-	spool->used_hpages -= delta;
-	/* If hugetlbfs_put_super couldn't free spool due to
-	* an outstanding quota reference, free it now. */
+
+	if (spool->max_hpages != -1)		/* maximum size accounting */
+		spool->used_hpages -= delta;
+
+	if (spool->min_hpages != -1) {		/* minimum size accounting */
+		if (spool->rsv_hpages + delta <= spool->min_hpages)
+			ret = 0;
+		else
+			ret = spool->rsv_hpages + delta - spool->min_hpages;
+
+		spool->rsv_hpages += delta;
+		if (spool->rsv_hpages > spool->min_hpages)
+			spool->rsv_hpages = spool->min_hpages;
+	}
+
+	/*
+	 * If hugetlbfs_put_super couldn't free spool due to an outstanding
+	 * quota reference, free it now.
+	 */
 	unlock_or_release_subpool(spool);
+
+	return ret;
 }
 
 static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
@@ -873,6 +926,14 @@ void free_huge_page(struct page *page)
 	restore_reserve = PagePrivate(page);
 	ClearPagePrivate(page);
 
+	/*
+	 * A return code of zero implies that the subpool will be under its
+	 * minimum size if the reservation is not restored after page is free.
+	 * Therefore, force restore_reserve operation.
+	 */
+	if (hugepage_subpool_put_pages(spool, 1) == 0)
+		restore_reserve = true;
+
 	spin_lock(&hugetlb_lock);
 	hugetlb_cgroup_uncharge_page(hstate_index(h),
 				     pages_per_huge_page(h), page);
@@ -890,7 +951,6 @@ void free_huge_page(struct page *page)
 		enqueue_huge_page(h, page);
 	}
 	spin_unlock(&hugetlb_lock);
-	hugepage_subpool_put_pages(spool, 1);
 }
 
 static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
@@ -1383,7 +1443,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 	if (chg < 0)
 		return ERR_PTR(-ENOMEM);
 	if (chg || avoid_reserve)
-		if (hugepage_subpool_get_pages(spool, 1))
+		if (hugepage_subpool_get_pages(spool, 1) < 0)
 			return ERR_PTR(-ENOSPC);
 
 	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
@@ -2451,6 +2511,7 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
 	struct resv_map *resv = vma_resv_map(vma);
 	struct hugepage_subpool *spool = subpool_vma(vma);
 	unsigned long reserve, start, end;
+	long gbl_reserve;
 
 	if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER))
 		return;
@@ -2463,8 +2524,12 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
 	kref_put(&resv->refs, resv_map_release);
 
 	if (reserve) {
-		hugetlb_acct_memory(h, -reserve);
-		hugepage_subpool_put_pages(spool, reserve);
+		/*
+		 * Decrement reserve counts.  The global reserve count may be
+		 * adjusted if the subpool has a minimum size.
+		 */
+		gbl_reserve = hugepage_subpool_put_pages(spool, reserve);
+		hugetlb_acct_memory(h, -gbl_reserve);
 	}
 }
 
@@ -3395,6 +3460,7 @@ int hugetlb_reserve_pages(struct inode *inode,
 	struct hstate *h = hstate_inode(inode);
 	struct hugepage_subpool *spool = subpool_inode(inode);
 	struct resv_map *resv_map;
+	long gbl_reserve;
 
 	/*
 	 * Only apply hugepage reservation if asked. At fault time, an
@@ -3431,8 +3497,13 @@ int hugetlb_reserve_pages(struct inode *inode,
 		goto out_err;
 	}
 
-	/* There must be enough pages in the subpool for the mapping */
-	if (hugepage_subpool_get_pages(spool, chg)) {
+	/*
+	 * There must be enough pages in the subpool for the mapping. If
+	 * the subpool has a minimum size, there may be some global
+	 * reservations already in place (gbl_reserve).
+	 */
+	gbl_reserve = hugepage_subpool_get_pages(spool, chg);
+	if (gbl_reserve < 0) {
 		ret = -ENOSPC;
 		goto out_err;
 	}
@@ -3441,9 +3512,10 @@ int hugetlb_reserve_pages(struct inode *inode,
 	 * Check enough hugepages are available for the reservation.
 	 * Hand the pages back to the subpool if there are not
 	 */
-	ret = hugetlb_acct_memory(h, chg);
+	ret = hugetlb_acct_memory(h, gbl_reserve);
 	if (ret < 0) {
-		hugepage_subpool_put_pages(spool, chg);
+		/* put back original number of pages, chg */
+		(void)hugepage_subpool_put_pages(spool, chg);
 		goto out_err;
 	}
 
@@ -3473,6 +3545,7 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 	struct resv_map *resv_map = inode_resv_map(inode);
 	long chg = 0;
 	struct hugepage_subpool *spool = subpool_inode(inode);
+	long gbl_reserve;
 
 	if (resv_map)
 		chg = region_truncate(resv_map, offset);
@@ -3480,8 +3553,12 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
 	inode->i_blocks -= (blocks_per_huge_page(h) * freed);
 	spin_unlock(&inode->i_lock);
 
-	hugepage_subpool_put_pages(spool, (chg - freed));
-	hugetlb_acct_memory(h, -(chg - freed));
+	/*
+	 * If the subpool has a minimum size, the number of global
+	 * reservations to be released may be adjusted.
+	 */
+	gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
+	hugetlb_acct_memory(h, -gbl_reserve);
 }
 
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
-- 
2.1.0

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[PATCH V3 3/4] hugetlbfs: accept subpool min_size mount option and setup accordingly

[Mike Kravetz]

Make 'min_size=<value>' be an option when mounting a hugetlbfs.  This
option takes the same value as the 'size' option.  min_size can be
specified without specifying size.  If both are specified, min_size
must be less that or equal to size else the mount will fail.  If
min_size is specified, then at mount time an attempt is made to reserve
min_size pages.  If the reservation fails, the mount fails.  At umount
time, the reserved pages are released.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 fs/hugetlbfs/inode.c    | 90 ++++++++++++++++++++++++++++++++++++++-----------
 include/linux/hugetlb.h |  3 +-
 mm/hugetlb.c            | 25 +++++++++++---
 3 files changed, 94 insertions(+), 24 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 5eba47f..38d2bc83e 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -47,9 +47,10 @@ struct hugetlbfs_config {
 	kuid_t   uid;
 	kgid_t   gid;
 	umode_t mode;
-	long	nr_blocks;
+	long	max_hpages;
 	long	nr_inodes;
 	struct hstate *hstate;
+	long    min_hpages;
 };
 
 struct hugetlbfs_inode_info {
@@ -73,7 +74,7 @@ int sysctl_hugetlb_shm_group;
 enum {
 	Opt_size, Opt_nr_inodes,
 	Opt_mode, Opt_uid, Opt_gid,
-	Opt_pagesize,
+	Opt_pagesize, Opt_min_size,
 	Opt_err,
 };
 
@@ -84,6 +85,7 @@ static const match_table_t tokens = {
 	{Opt_uid,	"uid=%u"},
 	{Opt_gid,	"gid=%u"},
 	{Opt_pagesize,	"pagesize=%s"},
+	{Opt_min_size,	"min_size=%s"},
 	{Opt_err,	NULL},
 };
 
@@ -761,14 +763,38 @@ static const struct super_operations hugetlbfs_ops = {
 	.show_options	= generic_show_options,
 };
 
+enum { NO_SIZE, SIZE_STD, SIZE_PERCENT };
+
+/*
+ * Convert size option passed from command line to number of huge pages
+ * in the pool specified by hstate.  Size option could be in bytes
+ * (val_type == SIZE_STD) or percentage of the pool (val_type == SIZE_PERCENT).
+ */
+static long long
+hugetlbfs_size_to_hpages(struct hstate *h, unsigned long long size_opt,
+								int val_type)
+{
+	if (val_type == NO_SIZE)
+		return -1;
+
+	if (val_type == SIZE_PERCENT) {
+		size_opt <<= huge_page_shift(h);
+		size_opt *= h->max_huge_pages;
+		do_div(size_opt, 100);
+	}
+
+	size_opt >>= huge_page_shift(h);
+	return size_opt;
+}
+
 static int
 hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
 {
 	char *p, *rest;
 	substring_t args[MAX_OPT_ARGS];
 	int option;
-	unsigned long long size = 0;
-	enum { NO_SIZE, SIZE_STD, SIZE_PERCENT } setsize = NO_SIZE;
+	unsigned long long max_size_opt = 0, min_size_opt = 0;
+	int max_val_type = NO_SIZE, min_val_type = NO_SIZE;
 
 	if (!options)
 		return 0;
@@ -806,10 +832,10 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
 			/* memparse() will accept a K/M/G without a digit */
 			if (!isdigit(*args[0].from))
 				goto bad_val;
-			size = memparse(args[0].from, &rest);
-			setsize = SIZE_STD;
+			max_size_opt = memparse(args[0].from, &rest);
+			max_val_type = SIZE_STD;
 			if (*rest == '%')
-				setsize = SIZE_PERCENT;
+				max_val_type = SIZE_PERCENT;
 			break;
 		}
 
@@ -832,6 +858,17 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
 			break;
 		}
 
+		case Opt_min_size: {
+			/* memparse() will accept a K/M/G without a digit */
+			if (!isdigit(*args[0].from))
+				goto bad_val;
+			min_size_opt = memparse(args[0].from, &rest);
+			min_val_type = SIZE_STD;
+			if (*rest == '%')
+				min_val_type = SIZE_PERCENT;
+			break;
+		}
+
 		default:
 			pr_err("Bad mount option: \"%s\"\n", p);
 			return -EINVAL;
@@ -839,15 +876,22 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
 		}
 	}
 
-	/* Do size after hstate is set up */
-	if (setsize > NO_SIZE) {
-		struct hstate *h = pconfig->hstate;
-		if (setsize == SIZE_PERCENT) {
-			size <<= huge_page_shift(h);
-			size *= h->max_huge_pages;
-			do_div(size, 100);
-		}
-		pconfig->nr_blocks = (size >> huge_page_shift(h));
+	/*
+	 * Use huge page pool size (in hstate) to convert the size
+	 * options to number of huge pages.  If NO_SIZE, -1 is returned.
+	 */
+	pconfig->max_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
+						max_size_opt, max_val_type);
+	pconfig->min_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
+						min_size_opt, min_val_type);
+
+	/*
+	 * If max_size was specified, then min_size must be smaller
+	 */
+	if (max_val_type > NO_SIZE &&
+	    pconfig->min_hpages > pconfig->max_hpages) {
+		pr_err("minimum size can not be greater than maximum size\n");
+		return -EINVAL;
 	}
 
 	return 0;
@@ -866,12 +910,13 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	save_mount_options(sb, data);
 
-	config.nr_blocks = -1; /* No limit on size by default */
+	config.max_hpages = -1; /* No limit on size by default */
 	config.nr_inodes = -1; /* No limit on number of inodes by default */
 	config.uid = current_fsuid();
 	config.gid = current_fsgid();
 	config.mode = 0755;
 	config.hstate = &default_hstate;
+	config.min_hpages = -1; /* No default minimum size */
 	ret = hugetlbfs_parse_options(data, &config);
 	if (ret)
 		return ret;
@@ -885,8 +930,15 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
 	sbinfo->max_inodes = config.nr_inodes;
 	sbinfo->free_inodes = config.nr_inodes;
 	sbinfo->spool = NULL;
-	if (config.nr_blocks != -1) {
-		sbinfo->spool = hugepage_new_subpool(config.nr_blocks);
+	/*
+	 * Allocate and initialize subpool if maximum or minimum size is
+	 * specified.  Any needed reservations (for minimim size) are taken
+	 * taken when the subpool is created.
+	 */
+	if (config.max_hpages != -1 || config.min_hpages != -1) {
+		sbinfo->spool = hugepage_new_subpool(config.hstate,
+							config.max_hpages,
+							config.min_hpages);
 		if (!sbinfo->spool)
 			goto out_free;
 	}
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2ec06a1..d2b41f4 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -44,7 +44,8 @@ extern int hugetlb_max_hstate __read_mostly;
 #define for_each_hstate(h) \
 	for ((h) = hstates; (h) < &hstates[hugetlb_max_hstate]; (h)++)
 
-struct hugepage_subpool *hugepage_new_subpool(long nr_blocks);
+struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages,
+						long min_hpages);
 void hugepage_put_subpool(struct hugepage_subpool *spool);
 
 int PageHuge(struct page *page);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 28a15c3..84511b6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -61,6 +61,9 @@ DEFINE_SPINLOCK(hugetlb_lock);
 static int num_fault_mutexes;
 static struct mutex *htlb_fault_mutex_table ____cacheline_aligned_in_smp;
 
+/* Forward declaration */
+static int hugetlb_acct_memory(struct hstate *h, long delta);
+
 static inline void unlock_or_release_subpool(struct hugepage_subpool *spool)
 {
 	bool free = (spool->count == 0) && (spool->used_hpages == 0);
@@ -68,12 +71,18 @@ static inline void unlock_or_release_subpool(struct hugepage_subpool *spool)
 	spin_unlock(&spool->lock);
 
 	/* If no pages are used, and no other handles to the subpool
-	 * remain, free the subpool the subpool remain */
-	if (free)
+	 * remain, give up any reservations mased on minimum size and
+	 * free the subpool */
+	if (free) {
+		if (spool->min_hpages != -1)
+			hugetlb_acct_memory(spool->hstate,
+						-spool->min_hpages);
 		kfree(spool);
+	}
 }
 
-struct hugepage_subpool *hugepage_new_subpool(long nr_blocks)
+struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages,
+						long min_hpages)
 {
 	struct hugepage_subpool *spool;
 
@@ -83,7 +92,15 @@ struct hugepage_subpool *hugepage_new_subpool(long nr_blocks)
 
 	spin_lock_init(&spool->lock);
 	spool->count = 1;
-	spool->max_hpages = nr_blocks;
+	spool->max_hpages = max_hpages;
+	spool->hstate = h;
+	spool->min_hpages = min_hpages;
+
+	if (min_hpages != -1 && hugetlb_acct_memory(h, min_hpages)) {
+		kfree(spool);
+		return NULL;
+	}
+	spool->rsv_hpages = min_hpages;
 
 	return spool;
 }
-- 
2.1.0

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[PATCH V3 4/4] hugetlbfs: document min_size mount option and cleanup

[Mike Kravetz]

Add min_size mount option to the hugetlbfs documentation.  Also,
add the missing pagesize option and mention that size can be
specified as bytes or a percentage of huge page pool.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 Documentation/vm/hugetlbpage.txt | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt
index f2d3a10..b32b9cd 100644
--- a/Documentation/vm/hugetlbpage.txt
+++ b/Documentation/vm/hugetlbpage.txt
@@ -267,21 +267,34 @@ call, then it is required that system administrator mount a file system of
 type hugetlbfs:
 
   mount -t hugetlbfs \
-	-o uid=<value>,gid=<value>,mode=<value>,size=<value>,nr_inodes=<value> \
-	none /mnt/huge
+	-o uid=<value>,gid=<value>,mode=<value>,pagesize=<value>,size=<value>,\
+	min_size=<value>,nr_inodes=<value> none /mnt/huge
 
 This command mounts a (pseudo) filesystem of type hugetlbfs on the directory
 /mnt/huge.  Any files created on /mnt/huge uses huge pages.  The uid and gid
 options sets the owner and group of the root of the file system.  By default
 the uid and gid of the current process are taken.  The mode option sets the
 mode of root of file system to value & 01777.  This value is given in octal.
-By default the value 0755 is picked. The size option sets the maximum value of
-memory (huge pages) allowed for that filesystem (/mnt/huge). The size is
-rounded down to HPAGE_SIZE.  The option nr_inodes sets the maximum number of
-inodes that /mnt/huge can use.  If the size or nr_inodes option is not
-provided on command line then no limits are set.  For size and nr_inodes
-options, you can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For
-example, size=2K has the same meaning as size=2048.
+By default the value 0755 is picked. If the paltform supports multiple huge
+page sizes, the pagesize option can be used to specify the huge page size and
+associated pool.  pagesize is specified in bytes.  If pagesize is not specified
+the paltform's default huge page size and associated pool will be used. The
+size option sets the maximum value of memory (huge pages) allowed for that
+filesystem (/mnt/huge).  The size option can be specified in bytes, or as a
+percentage of the specified huge page pool (nr_hugepages).  The size is
+rounded down to HPAGE_SIZE boundary.  The min_size option sets the minimum
+value of memory (huge pages) allowed for the filesystem.  min_size can be
+specified in the same way as size, either bytes or a percentage of the
+huge page pool.  At mount time, the number of huge pages specified by
+min_size are reserved for use by the filesystem.  If there are not enough
+free huge pages available, the mount will fail.  As huge pages are allocated
+to the filesystem and freed, the reserve count is adjusted so that the sum
+of allocated and reserved huge pages is always at least min_size.  The option
+nr_inodes sets the maximum number of inodes that /mnt/huge can use.  If the
+size, min_size or nr_inodes option is not provided on command line then
+no limits are set.  For pagesize, size, min_size and nr_inodes options, you
+can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For example, size=2K
+has the same meaning as size=2048.
 
 While read system calls are supported on files that reside on hugetlb
 file systems, write system calls are not.
-- 
2.1.0

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