Re: [PATCH 2/2] shmem: Add shmem_read_folio() and shmem_read_folio_gfp()

[kernel test robot <lkp@intel.com>]

Hi Matthew,

I love your patch! Perhaps something to improve:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v6.2-rc7 next-20230206]
[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/Matthew-Wilcox-Oracle/shmem-Add-shmem_read_folio-and-shmem_read_folio_gfp/20230207-002746
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230206162520.4029022-2-willy%40infradead.org
patch subject: [PATCH 2/2] shmem: Add shmem_read_folio() and shmem_read_folio_gfp()
config: i386-tinyconfig (https://download.01.org/0day-ci/archive/20230207/202302070249.AUvSISRY-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/ceb56c1ceea709ec0b10ed07e327bb4ae566bba5
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Matthew-Wilcox-Oracle/shmem-Add-shmem_read_folio-and-shmem_read_folio_gfp/20230207-002746
        git checkout ceb56c1ceea709ec0b10ed07e327bb4ae566bba5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   mm/shmem.c:4164:13: warning: no previous prototype for 'shmem_init' [-Wmissing-prototypes]
    4164 | void __init shmem_init(void)
         |             ^~~~~~~~~~
   mm/shmem.c:4172:5: warning: no previous prototype for 'shmem_unuse' [-Wmissing-prototypes]
    4172 | int shmem_unuse(unsigned int type)
         |     ^~~~~~~~~~~
   mm/shmem.c:4177:5: warning: no previous prototype for 'shmem_lock' [-Wmissing-prototypes]
    4177 | int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
         |     ^~~~~~~~~~
   mm/shmem.c:4182:6: warning: no previous prototype for 'shmem_unlock_mapping' [-Wmissing-prototypes]
    4182 | void shmem_unlock_mapping(struct address_space *mapping)
         |      ^~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4187:15: warning: no previous prototype for 'shmem_get_unmapped_area' [-Wmissing-prototypes]
    4187 | unsigned long shmem_get_unmapped_area(struct file *file,
         |               ^~~~~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4195:6: warning: no previous prototype for 'shmem_truncate_range' [-Wmissing-prototypes]
    4195 | void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
         |      ^~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4255:14: warning: no previous prototype for 'shmem_kernel_file_setup' [-Wmissing-prototypes]
    4255 | struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
         |              ^~~~~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4266:14: warning: no previous prototype for 'shmem_file_setup' [-Wmissing-prototypes]
    4266 | struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
         |              ^~~~~~~~~~~~~~~~
   mm/shmem.c:4279:14: warning: no previous prototype for 'shmem_file_setup_with_mnt' [-Wmissing-prototypes]
    4279 | struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
         |              ^~~~~~~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4290:5: warning: no previous prototype for 'shmem_zero_setup' [-Wmissing-prototypes]
    4290 | int shmem_zero_setup(struct vm_area_struct *vma)
         |     ^~~~~~~~~~~~~~~~
>> mm/shmem.c:4328:15: warning: no previous prototype for 'shmem_read_folio_gfp' [-Wmissing-prototypes]
    4328 | struct folio *shmem_read_folio_gfp(struct address_space *mapping,
         |               ^~~~~~~~~~~~~~~~~~~~
   mm/shmem.c:4353:14: warning: no previous prototype for 'shmem_read_mapping_page_gfp' [-Wmissing-prototypes]
    4353 | struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
         |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/shmem_read_folio_gfp +4328 mm/shmem.c

  4259	
  4260	/**
  4261	 * shmem_file_setup - get an unlinked file living in tmpfs
  4262	 * @name: name for dentry (to be seen in /proc/<pid>/maps
  4263	 * @size: size to be set for the file
  4264	 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
  4265	 */
> 4266	struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
  4267	{
  4268		return __shmem_file_setup(shm_mnt, name, size, flags, 0);
  4269	}
  4270	EXPORT_SYMBOL_GPL(shmem_file_setup);
  4271	
  4272	/**
  4273	 * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
  4274	 * @mnt: the tmpfs mount where the file will be created
  4275	 * @name: name for dentry (to be seen in /proc/<pid>/maps
  4276	 * @size: size to be set for the file
  4277	 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
  4278	 */
  4279	struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
  4280					       loff_t size, unsigned long flags)
  4281	{
  4282		return __shmem_file_setup(mnt, name, size, flags, 0);
  4283	}
  4284	EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
  4285	
  4286	/**
  4287	 * shmem_zero_setup - setup a shared anonymous mapping
  4288	 * @vma: the vma to be mmapped is prepared by do_mmap
  4289	 */
  4290	int shmem_zero_setup(struct vm_area_struct *vma)
  4291	{
  4292		struct file *file;
  4293		loff_t size = vma->vm_end - vma->vm_start;
  4294	
  4295		/*
  4296		 * Cloning a new file under mmap_lock leads to a lock ordering conflict
  4297		 * between XFS directory reading and selinux: since this file is only
  4298		 * accessible to the user through its mapping, use S_PRIVATE flag to
  4299		 * bypass file security, in the same way as shmem_kernel_file_setup().
  4300		 */
  4301		file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
  4302		if (IS_ERR(file))
  4303			return PTR_ERR(file);
  4304	
  4305		if (vma->vm_file)
  4306			fput(vma->vm_file);
  4307		vma->vm_file = file;
  4308		vma->vm_ops = &shmem_anon_vm_ops;
  4309	
  4310		return 0;
  4311	}
  4312	
  4313	/**
  4314	 * shmem_read_folio_gfp - read into page cache, using specified page allocation flags.
  4315	 * @mapping:	the folio's address_space
  4316	 * @index:	the folio index
  4317	 * @gfp:	the page allocator flags to use if allocating
  4318	 *
  4319	 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
  4320	 * with any new page allocations done using the specified allocation flags.
  4321	 * But read_cache_page_gfp() uses the ->read_folio() method: which does not
  4322	 * suit tmpfs, since it may have pages in swapcache, and needs to find those
  4323	 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
  4324	 *
  4325	 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
  4326	 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
  4327	 */
> 4328	struct folio *shmem_read_folio_gfp(struct address_space *mapping,
  4329			pgoff_t index, gfp_t gfp)
  4330	{
  4331	#ifdef CONFIG_SHMEM
  4332		struct inode *inode = mapping->host;
  4333		struct folio *folio;
  4334		int error;
  4335	
  4336		BUG_ON(!shmem_mapping(mapping));
  4337		error = shmem_get_folio_gfp(inode, index, &folio, SGP_CACHE,
  4338					  gfp, NULL, NULL, NULL);
  4339		if (error)
  4340			return ERR_PTR(error);
  4341	
  4342		folio_unlock(folio);
  4343		return folio;
  4344	#else
  4345		/*
  4346		 * The tiny !SHMEM case uses ramfs without swap
  4347		 */
  4348		return mapping_read_folio_gfp(mapping, index, gfp);
  4349	#endif
  4350	}
  4351	EXPORT_SYMBOL_GPL(shmem_read_folio_gfp);
  4352	

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