| Message ID | 20201225135119.3666763-1-almaz.alexandrovich@paragon-software.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | NTFS read-write driver GPL implementation by Paragon Software | expand |
On Fri, Dec 25, 2020 at 04:51:13PM +0300, Konstantin Komarov wrote: > +static int ntfs_readdir(struct file *file, struct dir_context *ctx) > +{ > + const struct INDEX_ROOT *root; > + u64 vbo; > + size_t bit; > + loff_t eod; > + int err = 0; > + struct inode *dir = file_inode(file); > + struct ntfs_inode *ni = ntfs_i(dir); > + struct super_block *sb = dir->i_sb; > + struct ntfs_sb_info *sbi = sb->s_fs_info; > + loff_t i_size = dir->i_size; I appreciate directories are never likely to exceed 4GB, but why not use i_size_read() here? > + u32 pos = ctx->pos; > + u8 *name = NULL; > + struct indx_node *node = NULL; > + u8 index_bits = ni->dir.index_bits; > + > + /* name is a buffer of PATH_MAX length */ > + static_assert(NTFS_NAME_LEN * 4 < PATH_MAX); > + > + if (ni->dir.changed) { > + ni->dir.changed = false; > + pos = 0; > + } I don't think that 'changed' as implemented is all that useful. If you have one reader and one-or-more writers, the reader will go back to the start, but if you have two readers and one-or-more writers, only one reader will see the 'changed' flag before the other one resets it. You need to use a sequence counter or something if you want this to be proof against multiple readers, and honestly I don't think it's worth it. POSIX says: : If a file is removed from or added to the directory after the most : recent call to opendir() or rewinddir(), whether a subsequent call to : readdir() returns an entry for that file is unspecified. > + eod = i_size + sbi->record_size; > + > + if (pos >= eod) > + return 0; > + > + if (!dir_emit_dots(file, ctx)) > + return 0; > + > + /* allocate PATH_MAX bytes */ > + name = __getname(); > + if (!name) > + return -ENOMEM; > + > + ni_lock(ni); What is ni_lock() protecting against here? You're being called under the protection of dir->i_rwsem, which excludes simultaneous calls to create, link, mknod, symlink, mkdir, unlink, rmdir and rename. > +const struct file_operations ntfs_dir_operations = { > + .llseek = generic_file_llseek, > + .read = generic_read_dir, > + .iterate = ntfs_readdir, This should probably be iterate_shared so multiple calls to readdir can be in progress at once (see Documentation/filesystems/porting)