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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: Tony Solomonik <tony.solomonik@gmail.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20240202121724.17461-2-tony.solomonik@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tony Solomonik 2024-02-02 14:17:23 +02:00 committed by Jens Axboe
parent a6e959bd3d
commit 5f0d594c60
2 changed files with 35 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/internal.h
View File

@ -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,

65
fs/open.c
View File

@ -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;
int error;
/* explicitly opened as large or we are on 64-bit box */
if (file->f_flags & O_LARGEFILE)
small = 0;
dentry = file->f_path.dentry;
inode = dentry->d_inode;
if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
return -EINVAL;
/* Cannot ftruncate over 2^31 bytes without large file support */
if (small && length > MAX_NON_LFS)
return -EINVAL;
/* Check IS_APPEND on real upper inode */
if (IS_APPEND(file_inode(file)))
return -EPERM;
sb_start_write(inode->i_sb);
error = security_file_truncate(file);
if (!error)
error = do_truncate(file_mnt_idmap(file), dentry, length,
ATTR_MTIME | ATTR_CTIME, file);
sb_end_write(inode->i_sb);
return error;
}
long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
struct fd f;
int error;
error = -EINVAL;
if (length < 0)
goto out;
error = -EBADF;
return -EINVAL;
f = fdget(fd);
if (!f.file)
goto out;
return -EBADF;
/* explicitly opened as large or we are on 64-bit box */
if (f.file->f_flags & O_LARGEFILE)
small = 0;
error = do_ftruncate(f.file, length, small);
dentry = f.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;
error = -EINVAL;
/* Cannot ftruncate over 2^31 bytes without large file support */
if (small && length > MAX_NON_LFS)
goto out_putf;
error = -EPERM;
/* Check IS_APPEND on real upper inode */
if (IS_APPEND(file_inode(f.file)))
goto out_putf;
sb_start_write(inode->i_sb);
error = security_file_truncate(f.file);
if (!error)
error = do_truncate(file_mnt_idmap(f.file), dentry, length,
ATTR_MTIME | ATTR_CTIME, f.file);
sb_end_write(inode->i_sb);
out_putf:
fdput(f);
out:
return error;
}