Commit 5f0d594c authored by Tony Solomonik's avatar Tony Solomonik Committed by Jens Axboe
Browse files

Add do_ftruncate that truncates a struct file 



do_sys_ftruncate receives a file descriptor, fgets the struct file, and
finally actually truncates the file.

do_ftruncate allows for passing in a file directly, with the caller
already holding a reference to it.

Signed-off-by: default avatarTony Solomonik <tony.solomonik@gmail.com>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20240202121724.17461-2-tony.solomonik@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a6e959bd

fs/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -183,6 +183,7 @@ extern struct open_how build_open_how(int flags, umode_t mode); 
extern int build_open_flags(const struct open_how *how, struct open_flags *op);

struct file *file_close_fd_locked(struct files_struct *files, unsigned fd);



long do_ftruncate(struct file *file, loff_t length, int small);

long do_sys_ftruncate(unsigned int fd, loff_t length, int small);

int chmod_common(const struct path *path, umode_t mode);

int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,

fs/open.c

+28 −25
Original line number Diff line number Diff line
@@ -154,49 +154,52 @@ COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length 
}

#endif



long do_sys_ftruncate(unsigned int fd, loff_t length, int small)

long do_ftruncate(struct file *file, loff_t length, int small)

{

	struct inode *inode;

	struct dentry *dentry;

	struct fd f;

	int error;



	error = -EINVAL;

	if (length < 0)

		goto out;

	error = -EBADF;

	f = fdget(fd);

	if (!f.file)

		goto out;



	/* explicitly opened as large or we are on 64-bit box */

	if (f.file->f_flags & O_LARGEFILE)

	if (file->f_flags & O_LARGEFILE)

		small = 0;



	dentry = f.file->f_path.dentry;

	dentry = file->f_path.dentry;

	inode = dentry->d_inode;

	error = -EINVAL;

	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))

		goto out_putf;

	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))

		return -EINVAL;



	error = -EINVAL;

	/* Cannot ftruncate over 2^31 bytes without large file support */

	if (small && length > MAX_NON_LFS)

		goto out_putf;

		return -EINVAL;



	error = -EPERM;

	/* Check IS_APPEND on real upper inode */

	if (IS_APPEND(file_inode(f.file)))

		goto out_putf;

	if (IS_APPEND(file_inode(file)))

		return -EPERM;

	sb_start_write(inode->i_sb);

	error = security_file_truncate(f.file);

	error = security_file_truncate(file);

	if (!error)

		error = do_truncate(file_mnt_idmap(f.file), dentry, length,

				    ATTR_MTIME | ATTR_CTIME, f.file);

		error = do_truncate(file_mnt_idmap(file), dentry, length,

				    ATTR_MTIME | ATTR_CTIME, file);

	sb_end_write(inode->i_sb);

out_putf:



	return error;

}



long do_sys_ftruncate(unsigned int fd, loff_t length, int small)

{

	struct fd f;

	int error;



	if (length < 0)

		return -EINVAL;

	f = fdget(fd);

	if (!f.file)

		return -EBADF;



	error = do_ftruncate(f.file, length, small);



	fdput(f);

out:

	return error;

}