Message-ID: <ed2cf936858c0fa14adbbd71e7638be489357df8.1757534913.git.lorenzo.stoakes@oracle.com>
Date: Wed, 10 Sep 2025 21:22:05 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
        Guo Ren <guoren@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        "David S . Miller" <davem@...emloft.net>,
        Andreas Larsson <andreas@...sler.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>, Nicolas Pitre <nico@...xnic.net>,
        Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, Tony Luck <tony.luck@...el.com>,
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        Alexander Viro <viro@...iv.linux.org.uk>,
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        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Hugh Dickins <hughd@...gle.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Uladzislau Rezki <urezki@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org, linux-mm@...ck.org,
        ntfs3@...ts.linux.dev, kexec@...ts.infradead.org,
        kasan-dev@...glegroups.com, Jason Gunthorpe <jgg@...dia.com>
Subject: [PATCH v2 10/16] mm/hugetlbfs: update hugetlbfs to use mmap_prepare

Since we can now perform actions after the VMA is established via
mmap_prepare, use desc->action_success_hook to set up the hugetlb lock once
the VMA is setup.

We also make changes throughout hugetlbfs to make this possible.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 fs/hugetlbfs/inode.c           | 30 +++++++------
 include/linux/hugetlb.h        |  9 +++-
 include/linux/hugetlb_inline.h | 15 ++++---
 mm/hugetlb.c                   | 77 ++++++++++++++++++++--------------
 4 files changed, 79 insertions(+), 52 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 3cfdf4091001..026bcc65bb79 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -96,8 +96,9 @@ static const struct fs_parameter_spec hugetlb_fs_parameters[] = {
 #define PGOFF_LOFFT_MAX \
 	(((1UL << (PAGE_SHIFT + 1)) - 1) <<  (BITS_PER_LONG - (PAGE_SHIFT + 1)))
 
-static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
+static int hugetlbfs_file_mmap_prepare(struct vm_area_desc *desc)
 {
+	struct file *file = desc->file;
 	struct inode *inode = file_inode(file);
 	loff_t len, vma_len;
 	int ret;
@@ -112,8 +113,8 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 	 * way when do_mmap unwinds (may be important on powerpc
 	 * and ia64).
 	 */
-	vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND);
-	vma->vm_ops = &hugetlb_vm_ops;
+	desc->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
+	desc->vm_ops = &hugetlb_vm_ops;
 
 	/*
 	 * page based offset in vm_pgoff could be sufficiently large to
@@ -122,16 +123,16 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 	 * sizeof(unsigned long).  So, only check in those instances.
 	 */
 	if (sizeof(unsigned long) == sizeof(loff_t)) {
-		if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
+		if (desc->pgoff & PGOFF_LOFFT_MAX)
 			return -EINVAL;
 	}
 
 	/* must be huge page aligned */
-	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
+	if (desc->pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
 		return -EINVAL;
 
-	vma_len = (loff_t)(vma->vm_end - vma->vm_start);
-	len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+	vma_len = (loff_t)vma_desc_size(desc);
+	len = vma_len + ((loff_t)desc->pgoff << PAGE_SHIFT);
 	/* check for overflow */
 	if (len < vma_len)
 		return -EINVAL;
@@ -141,7 +142,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	ret = -ENOMEM;
 
-	vm_flags = vma->vm_flags;
+	vm_flags = desc->vm_flags;
 	/*
 	 * for SHM_HUGETLB, the pages are reserved in the shmget() call so skip
 	 * reserving here. Note: only for SHM hugetlbfs file, the inode
@@ -151,17 +152,20 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 		vm_flags |= VM_NORESERVE;
 
 	if (hugetlb_reserve_pages(inode,
-				vma->vm_pgoff >> huge_page_order(h),
-				len >> huge_page_shift(h), vma,
-				vm_flags) < 0)
+			desc->pgoff >> huge_page_order(h),
+			len >> huge_page_shift(h), desc,
+			vm_flags) < 0)
 		goto out;
 
 	ret = 0;
-	if (vma->vm_flags & VM_WRITE && inode->i_size < len)
+	if ((desc->vm_flags & VM_WRITE) && inode->i_size < len)
 		i_size_write(inode, len);
 out:
 	inode_unlock(inode);
 
+	/* Allocate the VMA lock after we set it up. */
+	if (!ret)
+		desc->action.success_hook = hugetlb_vma_lock_alloc;
 	return ret;
 }
 
@@ -1219,7 +1223,7 @@ static void init_once(void *foo)
 
 static const struct file_operations hugetlbfs_file_operations = {
 	.read_iter		= hugetlbfs_read_iter,
-	.mmap			= hugetlbfs_file_mmap,
+	.mmap_prepare		= hugetlbfs_file_mmap_prepare,
 	.fsync			= noop_fsync,
 	.get_unmapped_area	= hugetlb_get_unmapped_area,
 	.llseek			= default_llseek,
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 526d27e88b3b..b39f2b70ccab 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -150,8 +150,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 			     struct folio **foliop);
 #endif /* CONFIG_USERFAULTFD */
 long hugetlb_reserve_pages(struct inode *inode, long from, long to,
-						struct vm_area_struct *vma,
-						vm_flags_t vm_flags);
+			   struct vm_area_desc *desc, vm_flags_t vm_flags);
 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 						long freed);
 bool folio_isolate_hugetlb(struct folio *folio, struct list_head *list);
@@ -280,6 +279,7 @@ bool is_hugetlb_entry_hwpoisoned(pte_t pte);
 void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
 void fixup_hugetlb_reservations(struct vm_area_struct *vma);
 void hugetlb_split(struct vm_area_struct *vma, unsigned long addr);
+int hugetlb_vma_lock_alloc(struct vm_area_struct *vma);
 
 #else /* !CONFIG_HUGETLB_PAGE */
 
@@ -466,6 +466,11 @@ static inline void fixup_hugetlb_reservations(struct vm_area_struct *vma)
 
 static inline void hugetlb_split(struct vm_area_struct *vma, unsigned long addr) {}
 
+static inline int hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
+{
+	return 0;
+}
+
 #endif /* !CONFIG_HUGETLB_PAGE */
 
 #ifndef pgd_write
diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h
index 0660a03d37d9..a27aa0162918 100644
--- a/include/linux/hugetlb_inline.h
+++ b/include/linux/hugetlb_inline.h
@@ -2,22 +2,27 @@
 #ifndef _LINUX_HUGETLB_INLINE_H
 #define _LINUX_HUGETLB_INLINE_H
 
-#ifdef CONFIG_HUGETLB_PAGE
-
 #include <linux/mm.h>
 
-static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
+#ifdef CONFIG_HUGETLB_PAGE
+
+static inline bool is_vm_hugetlb_flags(vm_flags_t vm_flags)
 {
-	return !!(vma->vm_flags & VM_HUGETLB);
+	return !!(vm_flags & VM_HUGETLB);
 }
 
 #else
 
-static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
+static inline bool is_vm_hugetlb_flags(vm_flags_t vm_flags)
 {
 	return false;
 }
 
 #endif
 
+static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
+{
+	return is_vm_hugetlb_flags(vma->vm_flags);
+}
+
 #endif
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d812ad8f0b9f..cb6eda43cb7f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -119,7 +119,6 @@ struct mutex *hugetlb_fault_mutex_table __ro_after_init;
 /* Forward declaration */
 static int hugetlb_acct_memory(struct hstate *h, long delta);
 static void hugetlb_vma_lock_free(struct vm_area_struct *vma);
-static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma);
 static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma);
 static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
 		unsigned long start, unsigned long end, bool take_locks);
@@ -417,17 +416,21 @@ static void hugetlb_vma_lock_free(struct vm_area_struct *vma)
 	}
 }
 
-static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
+/*
+ * vma specific semaphore used for pmd sharing and fault/truncation
+ * synchronization
+ */
+int hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
 {
 	struct hugetlb_vma_lock *vma_lock;
 
 	/* Only establish in (flags) sharable vmas */
 	if (!vma || !(vma->vm_flags & VM_MAYSHARE))
-		return;
+		return 0;
 
 	/* Should never get here with non-NULL vm_private_data */
 	if (vma->vm_private_data)
-		return;
+		return -EINVAL;
 
 	vma_lock = kmalloc(sizeof(*vma_lock), GFP_KERNEL);
 	if (!vma_lock) {
@@ -442,13 +445,15 @@ static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
 		 * allocation failure.
 		 */
 		pr_warn_once("HugeTLB: unable to allocate vma specific lock\n");
-		return;
+		return -EINVAL;
 	}
 
 	kref_init(&vma_lock->refs);
 	init_rwsem(&vma_lock->rw_sema);
 	vma_lock->vma = vma;
 	vma->vm_private_data = vma_lock;
+
+	return 0;
 }
 
 /* Helper that removes a struct file_region from the resv_map cache and returns
@@ -1180,20 +1185,28 @@ static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
 	}
 }
 
-static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
+static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
 {
-	VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
-	VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
+	VM_WARN_ON_ONCE_VMA(!is_vm_hugetlb_page(vma), vma);
+	VM_WARN_ON_ONCE_VMA(vma->vm_flags & VM_MAYSHARE, vma);
 
-	set_vma_private_data(vma, (unsigned long)map);
+	set_vma_private_data(vma, get_vma_private_data(vma) | flags);
 }
 
-static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
+static void set_vma_desc_resv_map(struct vm_area_desc *desc, struct resv_map *map)
 {
-	VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
-	VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
+	VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
+	VM_WARN_ON_ONCE(desc->vm_flags & VM_MAYSHARE);
 
-	set_vma_private_data(vma, get_vma_private_data(vma) | flags);
+	desc->private_data = map;
+}
+
+static void set_vma_desc_resv_flags(struct vm_area_desc *desc, unsigned long flags)
+{
+	VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
+	VM_WARN_ON_ONCE(desc->vm_flags & VM_MAYSHARE);
+
+	desc->private_data = (void *)((unsigned long)desc->private_data | flags);
 }
 
 static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
@@ -1203,6 +1216,13 @@ static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
 	return (get_vma_private_data(vma) & flag) != 0;
 }
 
+static bool is_vma_desc_resv_set(struct vm_area_desc *desc, unsigned long flag)
+{
+	VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
+
+	return ((unsigned long)desc->private_data) & flag;
+}
+
 bool __vma_private_lock(struct vm_area_struct *vma)
 {
 	return !(vma->vm_flags & VM_MAYSHARE) &&
@@ -7225,9 +7245,9 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
  */
 
 long hugetlb_reserve_pages(struct inode *inode,
-					long from, long to,
-					struct vm_area_struct *vma,
-					vm_flags_t vm_flags)
+		long from, long to,
+		struct vm_area_desc *desc,
+		vm_flags_t vm_flags)
 {
 	long chg = -1, add = -1, spool_resv, gbl_resv;
 	struct hstate *h = hstate_inode(inode);
@@ -7242,12 +7262,6 @@ long hugetlb_reserve_pages(struct inode *inode,
 		return -EINVAL;
 	}
 
-	/*
-	 * vma specific semaphore used for pmd sharing and fault/truncation
-	 * synchronization
-	 */
-	hugetlb_vma_lock_alloc(vma);
-
 	/*
 	 * Only apply hugepage reservation if asked. At fault time, an
 	 * attempt will be made for VM_NORESERVE to allocate a page
@@ -7260,9 +7274,9 @@ long hugetlb_reserve_pages(struct inode *inode,
 	 * Shared mappings base their reservation on the number of pages that
 	 * are already allocated on behalf of the file. Private mappings need
 	 * to reserve the full area even if read-only as mprotect() may be
-	 * called to make the mapping read-write. Assume !vma is a shm mapping
+	 * called to make the mapping read-write. Assume !desc is a shm mapping
 	 */
-	if (!vma || vma->vm_flags & VM_MAYSHARE) {
+	if (!desc || desc->vm_flags & VM_MAYSHARE) {
 		/*
 		 * resv_map can not be NULL as hugetlb_reserve_pages is only
 		 * called for inodes for which resv_maps were created (see
@@ -7279,8 +7293,8 @@ long hugetlb_reserve_pages(struct inode *inode,
 
 		chg = to - from;
 
-		set_vma_resv_map(vma, resv_map);
-		set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
+		set_vma_desc_resv_map(desc, resv_map);
+		set_vma_desc_resv_flags(desc, HPAGE_RESV_OWNER);
 	}
 
 	if (chg < 0)
@@ -7290,7 +7304,7 @@ long hugetlb_reserve_pages(struct inode *inode,
 				chg * pages_per_huge_page(h), &h_cg) < 0)
 		goto out_err;
 
-	if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
+	if (desc && !(desc->vm_flags & VM_MAYSHARE) && h_cg) {
 		/* For private mappings, the hugetlb_cgroup uncharge info hangs
 		 * of the resv_map.
 		 */
@@ -7324,7 +7338,7 @@ long hugetlb_reserve_pages(struct inode *inode,
 	 * consumed reservations are stored in the map. Hence, nothing
 	 * else has to be done for private mappings here
 	 */
-	if (!vma || vma->vm_flags & VM_MAYSHARE) {
+	if (!desc || desc->vm_flags & VM_MAYSHARE) {
 		add = region_add(resv_map, from, to, regions_needed, h, h_cg);
 
 		if (unlikely(add < 0)) {
@@ -7378,16 +7392,15 @@ long hugetlb_reserve_pages(struct inode *inode,
 	hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
 					    chg * pages_per_huge_page(h), h_cg);
 out_err:
-	hugetlb_vma_lock_free(vma);
-	if (!vma || vma->vm_flags & VM_MAYSHARE)
+	if (!desc || desc->vm_flags & VM_MAYSHARE)
 		/* 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)) {
+	if (desc && is_vma_desc_resv_set(desc, HPAGE_RESV_OWNER)) {
 		kref_put(&resv_map->refs, resv_map_release);
-		set_vma_resv_map(vma, NULL);
+		set_vma_desc_resv_map(desc, NULL);
 	}
 	return chg < 0 ? chg : add < 0 ? add : -EINVAL;
 }
-- 
2.51.0

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