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[RFC v5 PATCH 0/9] hugetlbfs: add fallocate support

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  [RFC v5 PATCH 0/9] hugetlbfs: add fallocate support Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 6/9] mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 9/9] mm: madvise allow remove operation for hugetlbfs Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 7/9] hugetlbfs: New huge_add_to_page_cache helper routine Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 5/9] mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 3/9] hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200
    [RFC v5 PATCH 2/9] mm/hugetlb: expose hugetlb fault mutex for use by fallocate Mike Kravetz <mike.kravetz@oracle.com> - 2015-06-23 02:50 +0200

#1170316 — [RFC v5 PATCH 0/9] hugetlbfs: add fallocate support

No major changes since last RFC.  Externalized existing hugetlb
fault mutex code.  Added more comments to alloc_huge_page reservation
handling as I could not come up with a good way to encapsulate.
libhugetlbfs test cases and man page updates will be included with
a later request for patch inclusion.

hugetlbfs is used today by applications that want a high degree of
control over huge page usage.  Often, large hugetlbfs files are used
to map a large number huge pages into the application processes.
The applications know when page ranges within these large files will
no longer be used, and ideally would like to release them back to
the subpool or global pools for other uses.  The fallocate() system
call provides an interface for preallocation and hole punching within
files.  This patch set adds fallocate functionality to hugetlbfs.

RFC v5:
  Simply made existing hugetlb fault mutex hash routine available for
    use by fallocate.
  Unable to come up with good reservation encapsulation routines for
    alloc_huge_page, so attempted to comment better.
RFC v4:
  Removed alloc_huge_page/hugetlb_reserve_pages race patches as already
    in mmotm
  Moved hugetlb_fix_reserve_counts in series as suggested by Naoya Horiguchi
  Inline'ed hugetlb_fault_mutex routines as suggested by Davidlohr Bueso and
    existing code changed to use new interfaces as suggested by Naoya
  fallocate preallocation code cleaned up and made simpler
  Modified alloc_huge_page to handle special case where allocation is
    for a hole punched area with spool reserves
RFC v3:
  Folded in patch for alloc_huge_page/hugetlb_reserve_pages race
    in current code
  fallocate allocation and hole punch is synchronized with page
    faults via existing mutex table
   hole punch uses existing hugetlb_vmtruncate_list instead of more
    generic unmap_mapping_range for unmapping
   Error handling for the case when region_del() fails
RFC v2:
  Addressed alignment and error handling issues noticed by Hillf Danton
  New region_del() routine for region tracking/resv_map of ranges
  Fixed several issues found during more extensive testing
  Error handling in region_del() when kmalloc() fails stills needs
    to be addressed
  madvise remove support remains

Mike Kravetz (9):
  mm/hugetlb: add region_del() to delete a specific range of entries
  mm/hugetlb: expose hugetlb fault mutex for use by fallocate
  hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete
  hugetlbfs: truncate_hugepages() takes a range of pages
  mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch
  mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate
  hugetlbfs: New huge_add_to_page_cache helper routine
  hugetlbfs: add hugetlbfs_fallocate()
  mm: madvise allow remove operation for hugetlbfs

 fs/hugetlbfs/inode.c    | 281 ++++++++++++++++++++++++++++++++++++++++++++----
 include/linux/hugetlb.h |  14 ++-
 mm/hugetlb.c            | 245 +++++++++++++++++++++++++++++------------
 mm/madvise.c            |   2 +-
 4 files changed, 456 insertions(+), 86 deletions(-)

-- 
2.1.0

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#1170317 — [RFC v5 PATCH 6/9] mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate

Areas hole punched by fallocate will not have entries in the
region/reserve map.  However, shared mappings with min_size subpool
reservations may still have reserved pages.  alloc_huge_page needs
to handle this special case and do the proper accounting.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 54 +++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 39 insertions(+), 15 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9d2859f..a485d9c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1600,32 +1600,56 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 	struct hugepage_subpool *spool = subpool_vma(vma);
 	struct hstate *h = hstate_vma(vma);
 	struct page *page;
-	long chg, commit;
+	long map_chg, map_commit;
+	long gbl_chg;
 	int ret, idx;
 	struct hugetlb_cgroup *h_cg;
 
 	idx = hstate_index(h);
 	/*
-	 * Processes that did not create the mapping will have no
-	 * reserves and will not have accounted against subpool
-	 * limit. Check that the subpool limit can be made before
-	 * satisfying the allocation MAP_NORESERVE mappings may also
-	 * need pages and subpool limit allocated allocated if no reserve
-	 * mapping overlaps.
+	 * Examine the region/reserve map to determine if the process
+	 * has a reservation for the page to be allocated.  A return
+	 * code of zero indicates a reservation exists (no change).
 	 */
-	chg = vma_needs_reservation(h, vma, addr);
-	if (chg < 0)
+	map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);
+	if (map_chg < 0)
 		return ERR_PTR(-ENOMEM);
-	if (chg || avoid_reserve)
-		if (hugepage_subpool_get_pages(spool, 1) < 0)
+
+	/*
+	 * Processes that did not create the mapping will have no
+	 * reserves as indicated by the region/reserve map. Check
+	 * that the allocation will not exceed the subpool limit.
+	 * Allocations for MAP_NORESERVE mappings also need to be
+	 * checked against any subpool limit.
+	 */
+	if (map_chg || avoid_reserve) {
+		gbl_chg = hugepage_subpool_get_pages(spool, 1);
+		if (gbl_chg < 0)
 			return ERR_PTR(-ENOSPC);
 
+		/*
+		 * Even though there was no reservation in the region/reserve
+		 * map, there could be reservations associated with the
+		 * subpool that can be used.  This would be indicated if the
+		 * return value of hugepage_subpool_get_pages() is zero.
+		 * However, if avoid_reserve is specified we still avoid even
+		 * the subpool reservations.
+		 */
+		if (avoid_reserve)
+			gbl_chg = 1;
+	}
+
 	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
 	if (ret)
 		goto out_subpool_put;
 
 	spin_lock(&hugetlb_lock);
-	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg);
+	/*
+	 * glb_chg is passed to indicate whether or not a page must be taken
+	 * from the global free pool (global change).  gbl_chg == 0 indicates
+	 * a reservation exists for the allocation.
+	 */
+	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
 	if (!page) {
 		spin_unlock(&hugetlb_lock);
 		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
@@ -1641,8 +1665,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 
 	set_page_private(page, (unsigned long)spool);
 
-	commit = vma_commit_reservation(h, vma, addr);
-	if (unlikely(chg > commit)) {
+	map_commit = vma_commit_reservation(h, vma, addr);
+	if (unlikely(map_chg > map_commit)) {
 		/*
 		 * The page was added to the reservation map between
 		 * vma_needs_reservation and vma_commit_reservation.
@@ -1662,7 +1686,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 out_uncharge_cgroup:
 	hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
 out_subpool_put:
-	if (chg || avoid_reserve)
+	if (map_chg || avoid_reserve)
 		hugepage_subpool_put_pages(spool, 1);
 	return ERR_PTR(-ENOSPC);
 }
-- 
2.1.0

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#1170319 — [RFC v5 PATCH 9/9] mm: madvise allow remove operation for hugetlbfs

Now that we have hole punching support for hugetlbfs, we can
also support the MADV_REMOVE interface to it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/madvise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index d215ea9..3c1b7f0 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -467,7 +467,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 
 	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */
 
-	if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
+	if (vma->vm_flags & VM_LOCKED)
 		return -EINVAL;
 
 	f = vma->vm_file;
-- 
2.1.0

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#1170320 — [RFC v5 PATCH 7/9] hugetlbfs: New huge_add_to_page_cache helper routine

Currently, there is  only a single place where hugetlbfs pages are
added to the page cache.  The new fallocate code be adding a second
one, so break the functionality out into its own helper.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb.h |  2 ++
 mm/hugetlb.c            | 27 ++++++++++++++++++---------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index e6ed378..71a24a7 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -330,6 +330,8 @@ struct huge_bootmem_page {
 struct page *alloc_huge_page_node(struct hstate *h, int nid);
 struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
 				unsigned long addr, int avoid_reserve);
+int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
+			pgoff_t idx);
 
 /* arch callback */
 int __init alloc_bootmem_huge_page(struct hstate *h);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a485d9c..77712c8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3239,6 +3239,23 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
 	return page != NULL;
 }
 
+int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
+			   pgoff_t idx)
+{
+	struct inode *inode = mapping->host;
+	struct hstate *h = hstate_inode(inode);
+	int err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+
+	if (err)
+		return err;
+	ClearPagePrivate(page);
+
+	spin_lock(&inode->i_lock);
+	inode->i_blocks += blocks_per_huge_page(h);
+	spin_unlock(&inode->i_lock);
+	return 0;
+}
+
 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			   struct address_space *mapping, pgoff_t idx,
 			   unsigned long address, pte_t *ptep, unsigned int flags)
@@ -3286,21 +3303,13 @@ retry:
 		set_page_huge_active(page);
 
 		if (vma->vm_flags & VM_MAYSHARE) {
-			int err;
-			struct inode *inode = mapping->host;
-
-			err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+			int err = huge_add_to_page_cache(page, mapping, idx);
 			if (err) {
 				put_page(page);
 				if (err == -EEXIST)
 					goto retry;
 				goto out;
 			}
-			ClearPagePrivate(page);
-
-			spin_lock(&inode->i_lock);
-			inode->i_blocks += blocks_per_huge_page(h);
-			spin_unlock(&inode->i_lock);
 		} else {
 			lock_page(page);
 			if (unlikely(anon_vma_prepare(vma))) {
-- 
2.1.0

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#1170321 — [RFC v5 PATCH 5/9] mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch

In vma_has_reserves(), the current assumption is that reserves are
always present for shared mappings.  However, this will not be the
case with fallocate hole punch.  When punching a hole, the present
page will be deleted as well as the region/reserve map entry (and
hence any reservation).  vma_has_reserves is passed "chg" which
indicates whether or not a region/reserve map is present.  Use
this to determine if reserves are actually present or were removed
via hole punch.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7cd4b67..9d2859f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -692,9 +692,19 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
 			return 0;
 	}
 
-	/* Shared mappings always use reserves */
-	if (vma->vm_flags & VM_MAYSHARE)
-		return 1;
+	if (vma->vm_flags & VM_MAYSHARE) {
+		/*
+		 * We know VM_NORESERVE is not set.  Therefore, there SHOULD
+		 * be a region map for all pages.  The only situation where
+		 * there is no region map is if a hole was punched via
+		 * fallocate.  In this case, there really are no reverves to
+		 * use.  This situation is indicated if chg != 0.
+		 */
+		if (chg)
+			return 0;
+		else
+			return 1;
+	}
 
 	/*
 	 * Only the process that called mmap() has reserves for
-- 
2.1.0

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#1170322 — [RFC v5 PATCH 3/9] hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete

fallocate hole punch will want to unmap a specific range of pages.
Modify the existing hugetlb_vmtruncate_list() routine to take a
start/end range.  If end is 0, this indicates all pages after start
should be unmapped.  This is the same as the existing truncate
functionality.  Modify existing callers to add 0 as end of range.

Since the routine will be used in hole punch as well as truncate
operations, it is more appropriately renamed to hugetlb_vmdelete_list().

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 fs/hugetlbfs/inode.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index e5a93d8..e9d4c8d 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -374,11 +374,15 @@ static void hugetlbfs_evict_inode(struct inode *inode)
 }
 
 static inline void
-hugetlb_vmtruncate_list(struct rb_root *root, pgoff_t pgoff)
+hugetlb_vmdelete_list(struct rb_root *root, pgoff_t start, pgoff_t end)
 {
 	struct vm_area_struct *vma;
 
-	vma_interval_tree_foreach(vma, root, pgoff, ULONG_MAX) {
+	/*
+	 * end == 0 indicates that the entire range after
+	 * start should be unmapped.
+	 */
+	vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
 		unsigned long v_offset;
 
 		/*
@@ -387,13 +391,20 @@ hugetlb_vmtruncate_list(struct rb_root *root, pgoff_t pgoff)
 		 * which overlap the truncated area starting at pgoff,
 		 * and no vma on a 32-bit arch can span beyond the 4GB.
 		 */
-		if (vma->vm_pgoff < pgoff)
-			v_offset = (pgoff - vma->vm_pgoff) << PAGE_SHIFT;
+		if (vma->vm_pgoff < start)
+			v_offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
 		else
 			v_offset = 0;
 
-		unmap_hugepage_range(vma, vma->vm_start + v_offset,
-				     vma->vm_end, NULL);
+		if (end) {
+			end = ((end - start) << PAGE_SHIFT) +
+			       vma->vm_start + v_offset;
+			if (end > vma->vm_end)
+				end = vma->vm_end;
+		} else
+			end = vma->vm_end;
+
+		unmap_hugepage_range(vma, vma->vm_start + v_offset, end, NULL);
 	}
 }
 
@@ -409,7 +420,7 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
 	i_size_write(inode, offset);
 	i_mmap_lock_write(mapping);
 	if (!RB_EMPTY_ROOT(&mapping->i_mmap))
-		hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
+		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
 	i_mmap_unlock_write(mapping);
 	truncate_hugepages(inode, offset);
 	return 0;
-- 
2.1.0

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#1170323 — [RFC v5 PATCH 2/9] mm/hugetlb: expose hugetlb fault mutex for use by fallocate

hugetlb page faults are currently synchronized by the table of
mutexes (htlb_fault_mutex_table).  fallocate code will need to
synchronize with the page fault code when it allocates or
deletes pages.  Expose interfaces so that fallocate operations
can be synchronized with page faults.  Minor name changes to
be more consistent with other global hugetlb symbols.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb.h |  5 +++++
 mm/hugetlb.c            | 20 ++++++++++----------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2050261..33c6b32 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -85,6 +85,11 @@ int dequeue_hwpoisoned_huge_page(struct page *page);
 bool isolate_huge_page(struct page *page, struct list_head *list);
 void putback_active_hugepage(struct page *page);
 void free_huge_page(struct page *page);
+extern struct mutex *hugetlb_fault_mutex_table;
+u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
+				struct vm_area_struct *vma,
+				struct address_space *mapping,
+				pgoff_t idx, unsigned long address);
 
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
 pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3fc2359..9657cca 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -64,7 +64,7 @@ DEFINE_SPINLOCK(hugetlb_lock);
  * prevent spurious OOMs when the hugepage pool is fully utilized.
  */
 static int num_fault_mutexes;
-static struct mutex *htlb_fault_mutex_table ____cacheline_aligned_in_smp;
+struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
 
 /* Forward declaration */
 static int hugetlb_acct_memory(struct hstate *h, long delta);
@@ -2347,7 +2347,7 @@ static void __exit hugetlb_exit(void)
 	}
 
 	kobject_put(hugepages_kobj);
-	kfree(htlb_fault_mutex_table);
+	kfree(hugetlb_fault_mutex_table);
 }
 module_exit(hugetlb_exit);
 
@@ -2380,12 +2380,12 @@ static int __init hugetlb_init(void)
 #else
 	num_fault_mutexes = 1;
 #endif
-	htlb_fault_mutex_table =
+	hugetlb_fault_mutex_table =
 		kmalloc(sizeof(struct mutex) * num_fault_mutexes, GFP_KERNEL);
-	BUG_ON(!htlb_fault_mutex_table);
+	BUG_ON(!hugetlb_fault_mutex_table);
 
 	for (i = 0; i < num_fault_mutexes; i++)
-		mutex_init(&htlb_fault_mutex_table[i]);
+		mutex_init(&hugetlb_fault_mutex_table[i]);
 	return 0;
 }
 module_init(hugetlb_init);
@@ -3316,7 +3316,7 @@ backout_unlocked:
 }
 
 #ifdef CONFIG_SMP
-static u32 fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
+u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
 			    struct vm_area_struct *vma,
 			    struct address_space *mapping,
 			    pgoff_t idx, unsigned long address)
@@ -3341,7 +3341,7 @@ static u32 fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
  * For uniprocesor systems we always use a single mutex, so just
  * return 0 and avoid the hashing overhead.
  */
-static u32 fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
+u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
 			    struct vm_area_struct *vma,
 			    struct address_space *mapping,
 			    pgoff_t idx, unsigned long address)
@@ -3389,8 +3389,8 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * get spurious allocation failures if two CPUs race to instantiate
 	 * the same page in the page cache.
 	 */
-	hash = fault_mutex_hash(h, mm, vma, mapping, idx, address);
-	mutex_lock(&htlb_fault_mutex_table[hash]);
+	hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping, idx, address);
+	mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
 	entry = huge_ptep_get(ptep);
 	if (huge_pte_none(entry)) {
@@ -3473,7 +3473,7 @@ out_ptl:
 		put_page(pagecache_page);
 	}
 out_mutex:
-	mutex_unlock(&htlb_fault_mutex_table[hash]);
+	mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 	/*
 	 * Generally it's safe to hold refcount during waiting page lock. But
 	 * here we just wait to defer the next page fault to avoid busy loop and
-- 
2.1.0

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