Commit 45cd0faa authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

vfs: add the fadvise() file operation 



This is going to be used by overlayfs and possibly useful
for other filesystems.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 17ef445f

Documentation/filesystems/vfs.txt

+3 −0
Original line number Diff line number Diff line
@@ -885,6 +885,7 @@ struct file_operations { 
	ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);

	int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t, u64);

	int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t, u64);

	int (*fadvise)(struct file *, loff_t, loff_t, int);

};



Again, all methods are called without any locks being held, unless
@@ -965,6 +966,8 @@ otherwise noted. 
  dedupe_file_range: called by the ioctl(2) system call for FIDEDUPERANGE

	command.



  fadvise: possibly called by the fadvise64() system call.



Note that the file operations are implemented by the specific

filesystem in which the inode resides. When opening a device node

(character or block special) most filesystems will call special

include/linux/fs.h

+5 −0
Original line number Diff line number Diff line
@@ -1763,6 +1763,7 @@ struct file_operations { 
			u64);

	int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,

			u64);

	int (*fadvise)(struct file *, loff_t, loff_t, int);

} __randomize_layout;



struct inode_operations {
@@ -3459,4 +3460,8 @@ static inline bool dir_relax_shared(struct inode *inode) 
extern bool path_noexec(const struct path *path);

extern void inode_nohighmem(struct inode *inode);



/* mm/fadvise.c */

extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,

		       int advice);



#endif /* _LINUX_FS_H */

mm/fadvise.c

+45 −33
Original line number Diff line number Diff line
@@ -27,9 +27,9 @@ 
 * deactivate the pages and clear PG_Referenced.

 */



int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)

static int generic_fadvise(struct file *file, loff_t offset, loff_t len,

			   int advice)

{

	struct fd f = fdget(fd);

	struct inode *inode;

	struct address_space *mapping;

	struct backing_dev_info *bdi;
@@ -37,22 +37,14 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) 
	pgoff_t start_index;

	pgoff_t end_index;

	unsigned long nrpages;

	int ret = 0;



	if (!f.file)

		return -EBADF;

	inode = file_inode(file);

	if (S_ISFIFO(inode->i_mode))

		return -ESPIPE;



	inode = file_inode(f.file);

	if (S_ISFIFO(inode->i_mode)) {

		ret = -ESPIPE;

		goto out;

	}



	mapping = f.file->f_mapping;

	if (!mapping || len < 0) {

		ret = -EINVAL;

		goto out;

	}

	mapping = file->f_mapping;

	if (!mapping || len < 0)

		return -EINVAL;



	bdi = inode_to_bdi(mapping->host);
@@ -67,9 +59,9 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) 
			/* no bad return value, but ignore advice */

			break;

		default:

			ret = -EINVAL;

			return -EINVAL;

		}

		goto out;

		return 0;

	}



	/*
@@ -85,21 +77,21 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) 


	switch (advice) {

	case POSIX_FADV_NORMAL:

		f.file->f_ra.ra_pages = bdi->ra_pages;

		spin_lock(&f.file->f_lock);

		f.file->f_mode &= ~FMODE_RANDOM;

		spin_unlock(&f.file->f_lock);

		file->f_ra.ra_pages = bdi->ra_pages;

		spin_lock(&file->f_lock);

		file->f_mode &= ~FMODE_RANDOM;

		spin_unlock(&file->f_lock);

		break;

	case POSIX_FADV_RANDOM:

		spin_lock(&f.file->f_lock);

		f.file->f_mode |= FMODE_RANDOM;

		spin_unlock(&f.file->f_lock);

		spin_lock(&file->f_lock);

		file->f_mode |= FMODE_RANDOM;

		spin_unlock(&file->f_lock);

		break;

	case POSIX_FADV_SEQUENTIAL:

		f.file->f_ra.ra_pages = bdi->ra_pages * 2;

		spin_lock(&f.file->f_lock);

		f.file->f_mode &= ~FMODE_RANDOM;

		spin_unlock(&f.file->f_lock);

		file->f_ra.ra_pages = bdi->ra_pages * 2;

		spin_lock(&file->f_lock);

		file->f_mode &= ~FMODE_RANDOM;

		spin_unlock(&file->f_lock);

		break;

	case POSIX_FADV_WILLNEED:

		/* First and last PARTIAL page! */
@@ -115,8 +107,7 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) 
		 * Ignore return value because fadvise() shall return

		 * success even if filesystem can't retrieve a hint,

		 */

		force_page_cache_readahead(mapping, f.file, start_index,

					   nrpages);

		force_page_cache_readahead(mapping, file, start_index, nrpages);

		break;

	case POSIX_FADV_NOREUSE:

		break;
@@ -183,9 +174,30 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) 
		}

		break;

	default:

		ret = -EINVAL;

		return -EINVAL;

	}

	return 0;

}

out:



int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)

{

	if (file->f_op->fadvise)

		return file->f_op->fadvise(file, offset, len, advice);



	return generic_fadvise(file, offset, len, advice);

}

EXPORT_SYMBOL(vfs_fadvise);



int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)

{

	struct fd f = fdget(fd);

	int ret;



	if (!f.file)

		return -EBADF;



	ret = vfs_fadvise(f.file, offset, len, advice);



	fdput(f);

	return ret;

}