[RFC][PATCH 2/2] HugeTLB mapping for drivers (export functions/identification of htlb mappings)

[Alexey Korolev <akorolev@infradead.org>]

This patch changes the procedures of htlb file identification. 
Since we can have non htlbfs files with htlb mapping we need to have
another approach for identification if mapping is hugetlb or not. 
This part is rather doubtful. Just checking of file operations seems
to be a bad approach as drivers (as well as ipc/shm) need have own
file_operations. The best place for identification of hugetlb mappings could be 
maping->flags. But I'm still not sure if it is the best place. 

This patch slightly modifies the procedure of getting hstate from inode.
If inode correspond to hugetlbfs - the hugetlbfs hstate will be
returned, otherwise hstate_nores.

Also this patch exports/declares some hugetlb/htlbfs functions for use of drivers.

 fs/hugetlbfs/inode.c    |    9 +++++----
 include/linux/hugetlb.h |   45 +++++++++++++++++++++++++++------------------
 include/linux/pagemap.h |   13 +++++++++++++
 include/linux/shm.h     |    5 -----
 ipc/shm.c               |   12 ------------
 mm/filemap.c            |    1 +
 6 files changed, 46 insertions(+), 39 deletions(-)
---
Signed-off-by: Alexey Korolev <akorolev@infradead.org>

diff -aurp ORIG/fs/hugetlbfs/inode.c NEW/fs/hugetlbfs/inode.c
--- ORIG/fs/hugetlbfs/inode.c	2009-07-05 05:58:48.000000000 +1200
+++ NEW/fs/hugetlbfs/inode.c	2009-07-11 10:23:00.000000000 +1200
@@ -34,9 +34,6 @@
 
 #include <asm/uaccess.h>
 
-/* some random number */
-#define HUGETLBFS_MAGIC	0x958458f6
-
 static const struct super_operations hugetlbfs_ops;
 static const struct address_space_operations hugetlbfs_aops;
 const struct file_operations hugetlbfs_file_operations;
@@ -77,7 +74,7 @@ static void huge_pagevec_release(struct 
 	pagevec_reinit(pvec);
 }
 
-static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
+int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct inode *inode = file->f_path.dentry->d_inode;
 	loff_t len, vma_len;
@@ -121,6 +118,7 @@ out:
 
 	return ret;
 }
+EXPORT_SYMBOL(hugetlbfs_file_mmap);
 
 /*
  * Called under down_write(mmap_sem).
@@ -183,6 +181,7 @@ full_search:
 	}
 }
 #endif
+EXPORT_SYMBOL(hugetlb_get_unmapped_area);
 
 static int
 hugetlbfs_read_actor(struct page *page, unsigned long offset,
@@ -512,6 +511,7 @@ static struct inode *hugetlbfs_get_inode
 			init_special_inode(inode, mode, dev);
 			break;
 		case S_IFREG:
+			mapping_set_hugetlb(inode->i_mapping);
 			inode->i_op = &hugetlbfs_inode_operations;
 			inode->i_fop = &hugetlbfs_file_operations;
 			break;
@@ -988,6 +988,7 @@ struct file *hugetlb_file_setup(const ch
 	if (!file)
 		goto out_dentry; /* inode is already attached */
 	ima_counts_get(file);
+	mapping_set_hugetlb(file->f_mapping);
 
 	return file;
 
diff -aurp ORIG/include/linux/hugetlb.h NEW/include/linux/hugetlb.h
--- ORIG/include/linux/hugetlb.h	2009-07-05 05:58:48.000000000 +1200
+++ NEW/include/linux/hugetlb.h	2009-07-13 06:58:00.000000000 +1200
@@ -5,6 +5,9 @@
 
 #ifdef CONFIG_HUGETLB_PAGE
 
+/* some random number */
+#define HUGETLBFS_MAGIC	0x958458f6
+
 #include <linux/mempolicy.h>
 #include <linux/shm.h>
 #include <asm/tlbflush.h>
@@ -61,6 +64,9 @@ int pud_huge(pud_t pmd);
 void hugetlb_change_protection(struct vm_area_struct *vma,
 		unsigned long address, unsigned long end, pgprot_t newprot);
 
+struct page *hugetlb_alloc_pages_node(int nid, gfp_t gfp_mask);
+void hugetlb_free_pages(struct page *page);
+
 #else /* !CONFIG_HUGETLB_PAGE */
 
 static inline int PageHuge(struct page *page)
@@ -102,6 +108,10 @@ static inline void hugetlb_report_meminf
 
 #define hugetlb_change_protection(vma, address, end, newprot)
 
+#define hugetlb_alloc_pages_node(nid, gfp_mask) 0
+#define hugetlb_free_pages(page) BUG();
+
+
 #ifndef HPAGE_MASK
 #define HPAGE_MASK	PAGE_MASK		/* Keep the compiler happy */
 #define HPAGE_SIZE	PAGE_SIZE
@@ -152,31 +162,26 @@ void hugetlb_put_quota(struct address_sp
 
 static inline int is_file_hugepages(struct file *file)
 {
-	if (file->f_op == &hugetlbfs_file_operations)
-		return 1;
-	if (is_file_shm_hugepages(file))
-		return 1;
-
-	return 0;
+	return mapping_hugetlb(file->f_mapping);
 }
 
-static inline void set_file_hugepages(struct file *file)
-{
-	file->f_op = &hugetlbfs_file_operations;
-}
+int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma);
+
+unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+			unsigned long len, unsigned long pgoff,
+			unsigned long flags);
+
 #else /* !CONFIG_HUGETLBFS */
 
 #define is_file_hugepages(file)			0
-#define set_file_hugepages(file)		BUG()
 #define hugetlb_file_setup(name,size,acctflag)	ERR_PTR(-ENOSYS)
 
+#define hugetlbfs_file_mmap(file, vma) (-ENOSYS)
+#define hugetlb_get_unmapped_area(file, addr, len, \
+		pgoff, flags) (-ENOSYS)
+
 #endif /* !CONFIG_HUGETLBFS */
 
-#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
-unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
-					unsigned long len, unsigned long pgoff,
-					unsigned long flags);
-#endif /* HAVE_ARCH_HUGETLB_UNMAPPED_AREA */
 
 #ifdef CONFIG_HUGETLB_PAGE
 
@@ -216,14 +221,18 @@ struct hstate *size_to_hstate(unsigned l
 
 extern struct hstate hstates[HUGE_MAX_HSTATE];
 extern unsigned int default_hstate_idx;
+extern struct hstate hstate_nores;
 
 #define default_hstate (hstates[default_hstate_idx])
 
 static inline struct hstate *hstate_inode(struct inode *i)
 {
 	struct hugetlbfs_sb_info *hsb;
-	hsb = HUGETLBFS_SB(i->i_sb);
-	return hsb->hstate;
+	if (i->i_sb->s_magic == HUGETLBFS_MAGIC) {
+		hsb = HUGETLBFS_SB(i->i_sb);
+		return hsb->hstate;
+	}
+	return &hstate_nores;
 }
 
 static inline struct hstate *hstate_file(struct file *f)
diff -aurp ORIG/include/linux/pagemap.h NEW/include/linux/pagemap.h
--- ORIG/include/linux/pagemap.h	2009-07-05 05:58:48.000000000 +1200
+++ NEW/include/linux/pagemap.h	2009-07-11 08:29:00.000000000 +1200
@@ -23,6 +23,7 @@ enum mapping_flags {
 	AS_ENOSPC	= __GFP_BITS_SHIFT + 1,	/* ENOSPC on async write */
 	AS_MM_ALL_LOCKS	= __GFP_BITS_SHIFT + 2,	/* under mm_take_all_locks() */
 	AS_UNEVICTABLE	= __GFP_BITS_SHIFT + 3,	/* e.g., ramdisk, SHM_LOCK */
+	AS_HUGETLB	= __GFP_BITS_SHIFT + 4,	/* under HUGE TLB */
 };
 
 static inline void mapping_set_error(struct address_space *mapping, int error)
@@ -52,6 +53,18 @@ static inline int mapping_unevictable(st
 	return !!mapping;
 }
 
+static inline void mapping_set_hugetlb(struct address_space *mapping)
+{
+	set_bit(AS_HUGETLB, &mapping->flags);
+}
+
+static inline int mapping_hugetlb(struct address_space *mapping)
+{
+	if (likely(mapping))
+		return test_bit(AS_HUGETLB, &mapping->flags);
+	return !!mapping;
+}
+
 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
 {
 	return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
diff -aurp ORIG/include/linux/shm.h NEW/include/linux/shm.h
--- ORIG/include/linux/shm.h	2009-07-05 05:58:48.000000000 +1200
+++ NEW/include/linux/shm.h	2009-07-11 08:29:00.000000000 +1200
@@ -105,17 +105,12 @@ struct shmid_kernel /* private to the ke
 
 #ifdef CONFIG_SYSVIPC
 long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr);
-extern int is_file_shm_hugepages(struct file *file);
 #else
 static inline long do_shmat(int shmid, char __user *shmaddr,
 				int shmflg, unsigned long *addr)
 {
 	return -ENOSYS;
 }
-static inline int is_file_shm_hugepages(struct file *file)
-{
-	return 0;
-}
 #endif
 
 #endif /* __KERNEL__ */
diff -aurp ORIG/ipc/shm.c NEW/ipc/shm.c
--- ORIG/ipc/shm.c	2009-07-05 05:58:48.000000000 +1200
+++ NEW/ipc/shm.c	2009-07-11 08:29:00.000000000 +1200
@@ -293,18 +293,6 @@ static unsigned long shm_get_unmapped_ar
 	return get_unmapped_area(sfd->file, addr, len, pgoff, flags);
 }
 
-int is_file_shm_hugepages(struct file *file)
-{
-	int ret = 0;
-
-	if (file->f_op == &shm_file_operations) {
-		struct shm_file_data *sfd;
-		sfd = shm_file_data(file);
-		ret = is_file_hugepages(sfd->file);
-	}
-	return ret;
-}
-
 static const struct file_operations shm_file_operations = {
 	.mmap		= shm_mmap,
 	.fsync		= shm_fsync,
diff -aurp ORIG/mm/filemap.c NEW/mm/filemap.c
--- ORIG/mm/filemap.c	2009-07-05 05:58:48.000000000 +1200
+++ NEW/mm/filemap.c	2009-07-11 08:29:00.000000000 +1200
@@ -146,6 +146,7 @@ void remove_from_page_cache(struct page 
 	spin_unlock_irq(&mapping->tree_lock);
 	mem_cgroup_uncharge_cache_page(page);
 }
+EXPORT_SYMBOL(remove_from_page_cache);
 
 static int sync_page(void *word)
 {

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