Change the shmem_huge_global_enabled() to return the suitable huge
order bitmap, and return 0 if huge pages are not allowed. This is a
preparation for supporting various huge orders allocation of tmpfs
in the following patches.

No functional changes.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/shmem.c | 45 ++++++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 579e58cb3262..361da46c4bd5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -549,37 +549,37 @@ static bool shmem_confirm_swap(struct address_space *mapping,
 
 static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
 
-static bool shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
-				      loff_t write_end, bool shmem_huge_force,
-				      unsigned long vm_flags)
+static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
+					      loff_t write_end, bool shmem_huge_force,
+					      unsigned long vm_flags)
 {
 	loff_t i_size;
 
 	if (HPAGE_PMD_ORDER > MAX_PAGECACHE_ORDER)
-		return false;
+		return 0;
 	if (!S_ISREG(inode->i_mode))
-		return false;
+		return 0;
 	if (shmem_huge == SHMEM_HUGE_DENY)
-		return false;
+		return 0;
 	if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
-		return true;
+		return BIT(HPAGE_PMD_ORDER);
 
 	switch (SHMEM_SB(inode->i_sb)->huge) {
 	case SHMEM_HUGE_ALWAYS:
-		return true;
+		return BIT(HPAGE_PMD_ORDER);
 	case SHMEM_HUGE_WITHIN_SIZE:
 		index = round_up(index + 1, HPAGE_PMD_NR);
 		i_size = max(write_end, i_size_read(inode));
 		i_size = round_up(i_size, PAGE_SIZE);
 		if (i_size >> PAGE_SHIFT >= index)
-			return true;
+			return BIT(HPAGE_PMD_ORDER);
 		fallthrough;
 	case SHMEM_HUGE_ADVISE:
 		if (vm_flags & VM_HUGEPAGE)
-			return true;
+			return BIT(HPAGE_PMD_ORDER);
 		fallthrough;
 	default:
-		return false;
+		return 0;
 	}
 }
 
@@ -774,11 +774,11 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 	return 0;
 }
 
-static bool shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
-				      loff_t write_end, bool shmem_huge_force,
-				      unsigned long vm_flags)
+static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
+					      loff_t write_end, bool shmem_huge_force,
+					      unsigned long vm_flags)
 {
-	return false;
+	return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
@@ -1173,8 +1173,11 @@ static int shmem_getattr(struct mnt_idmap *idmap,
 	generic_fillattr(idmap, request_mask, inode, stat);
 	inode_unlock_shared(inode);
 
-	if (shmem_huge_global_enabled(inode, 0, 0, false, 0))
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (shmem_huge_global_enabled(inode, 0, 0, false, 0) ==
+	    BIT(HPAGE_PMD_ORDER))
 		stat->blksize = HPAGE_PMD_SIZE;
+#endif
 
 	if (request_mask & STATX_BTIME) {
 		stat->result_mask |= STATX_BTIME;
@@ -1682,21 +1685,21 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	unsigned long mask = READ_ONCE(huge_shmem_orders_always);
 	unsigned long within_size_orders = READ_ONCE(huge_shmem_orders_within_size);
 	unsigned long vm_flags = vma ? vma->vm_flags : 0;
-	bool global_huge;
+	unsigned int global_orders;
 	loff_t i_size;
 	int order;
 
 	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags)))
 		return 0;
 
-	global_huge = shmem_huge_global_enabled(inode, index, write_end,
-						shmem_huge_force, vm_flags);
+	global_orders = shmem_huge_global_enabled(inode, index, write_end,
+						  shmem_huge_force, vm_flags);
 	if (!vma || !vma_is_anon_shmem(vma)) {
 		/*
 		 * For tmpfs, we now only support PMD sized THP if huge page
 		 * is enabled, otherwise fallback to order 0.
 		 */
-		return global_huge ? BIT(HPAGE_PMD_ORDER) : 0;
+		return global_orders;
 	}
 
 	/*
@@ -1729,7 +1732,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	if (vm_flags & VM_HUGEPAGE)
 		mask |= READ_ONCE(huge_shmem_orders_madvise);
 
-	if (global_huge)
+	if (global_orders > 0)
 		mask |= READ_ONCE(huge_shmem_orders_inherit);
 
 	return THP_ORDERS_ALL_FILE_DEFAULT & mask;
-- 
2.39.3

Hi Baolin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on next-20241108]
[cannot apply to linus/master v6.12-rc6]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Baolin-Wang/mm-factor-out-the-order-calculation-into-a-new-helper/20241108-121545
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/a0d41cdc3491878260277e8c18a3e71deb2bc1fb.1731038280.git.baolin.wang%40linux.alibaba.com
patch subject: [PATCH 2/4] mm: shmem: change shmem_huge_global_enabled() to return huge order bitmap
config: arc-allnoconfig (https://download.01.org/0day-ci/archive/20241108/202411082236.7mwWSsNe-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241108/202411082236.7mwWSsNe-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411082236.7mwWSsNe-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/shmem.c:777:21: warning: 'shmem_huge_global_enabled' defined but not used [-Wunused-function]
     777 | static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/shmem_huge_global_enabled +777 mm/shmem.c

   776	
 > 777	static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
   778						      loff_t write_end, bool shmem_huge_force,
   779						      unsigned long vm_flags)
   780	{
   781		return 0;
   782	}
   783	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
   784	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki