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>

diff --git a/fs/internal.h b/fs/internal.h
index b67406435fc02763299e8732fa4cf6dfe1d51bf6..8509cbd6d115d9028b0be26dc4da6d2690f09bbc 100644 (file)
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -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,

diff --git a/fs/open.c b/fs/open.c
index a84d21e55c391eebdf662c7fa8c9d5b2aef8efd2..0410cb52bb4b73ebe94c9d4b1c9b3d789db06cc7 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -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;
 }