Commit 1ab5b82f authored by Piotr Sarna's avatar Piotr Sarna Committed by Linus Torvalds
Browse files

hugetlbfs: add O_TMPFILE support 

With hugetlbfs, a common pattern for mapping anonymous huge pages is to
create a temporary file first.  Currently libraries like libhugetlbfs
and seastar create these with a standard mkstemp+unlink trick, but it
would be more robust to be able to simply pass the O_TMPFILE flag to
open().  O_TMPFILE is already supported by several file systems like
ext4 and xfs.  The implementation simply uses the existi= ng d_tmpfile
utility function to instantiate the dcache entry for the file.

Tested manually by successfully creating a temporary file by opening it
with (O_TMPFILE|O_RDWR) on mounted hugetlbfs and successfully mapping 2M
huge pages with it.  Without the patch, trying to open a file with
O_TMPFILE results in -ENOSUP.

Link: http://lkml.kernel.org/r/bc9383eff6e1374d79f3a92257ae829ba1e6ae60.1573285189.git.p.sarna@tlen.pl


Signed-off-by: default avatarPiotr Sarna <p.sarna@tlen.pl>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1f9dccb2

fs/hugetlbfs/inode.c

+24 −4
Original line number Diff line number Diff line
@@ -815,8 +815,11 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb, 
/*

 * File creation. Allocate an inode, and we're done..

 */

static int hugetlbfs_mknod(struct inode *dir,

			struct dentry *dentry, umode_t mode, dev_t dev)

static int do_hugetlbfs_mknod(struct inode *dir,

			struct dentry *dentry,

			umode_t mode,

			dev_t dev,

			bool tmpfile)

{

	struct inode *inode;

	int error = -ENOSPC;
@@ -824,13 +827,23 @@ static int hugetlbfs_mknod(struct inode *dir, 
	inode = hugetlbfs_get_inode(dir->i_sb, dir, mode, dev);

	if (inode) {

		dir->i_ctime = dir->i_mtime = current_time(dir);

		if (tmpfile) {

			d_tmpfile(dentry, inode);

		} else {

			d_instantiate(dentry, inode);

			dget(dentry);/* Extra count - pin the dentry in core */

		}

		error = 0;

	}

	return error;

}



static int hugetlbfs_mknod(struct inode *dir,

			struct dentry *dentry, umode_t mode, dev_t dev)

{

	return do_hugetlbfs_mknod(dir, dentry, mode, dev, false);

}



static int hugetlbfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

{

	int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
@@ -844,6 +857,12 @@ static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, umode_t mo 
	return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);

}



static int hugetlbfs_tmpfile(struct inode *dir,

			struct dentry *dentry, umode_t mode)

{

	return do_hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0, true);

}



static int hugetlbfs_symlink(struct inode *dir,

			struct dentry *dentry, const char *symname)

{
@@ -1102,6 +1121,7 @@ static const struct inode_operations hugetlbfs_dir_inode_operations = { 
	.mknod		= hugetlbfs_mknod,

	.rename		= simple_rename,

	.setattr	= hugetlbfs_setattr,

	.tmpfile	= hugetlbfs_tmpfile,

};



static const struct inode_operations hugetlbfs_inode_operations = {