On Mon, 13 Dec 2010 15:22:10 +0800 Shaohua Li <[email protected]> wrote:
> Add an ioctl to dump filesystem's metadata in memory in vfs. Userspace > collects > such info and uses it to do metadata readahead. > Filesystem can hook to super_operations.metadata_incore to get metadata in > specific approach. Next patch will give an example how to implement > .metadata_incore in btrfs. > Please cc Michael Kerrisk <[email protected]> and [email protected]. I'm sure that assistance writing the manpage would be appreciated. > > ... > > /* > + * Copy info about metadata in memory to userspace > + * Returns: > + * > 0, number of metadata_incore_ent entries copied to userspace > + * = 0, no more metadata > + * < 0, error > + */ > +static int ioctl_metadata_incore(struct file *filp, void __user *argp) > +{ > + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; > + struct metadata_incore_args args; > + struct metadata_incore_ent ent; > + loff_t offset, last_offset = 0; > + ssize_t size, last_size = 0; > + __u64 __user vec_addr; > + int entries = 0; > + > + if (!sb->s_op->metadata_incore) > + return -EOPNOTSUPP; EOPNOTSUPP is a networking errno - it doesn't seem appropriate for an fs ioctl. > + if (copy_from_user(&args, (struct metadata_incore_args __user *)argp, Unneeded typecast. > + sizeof(args))) > + return -EFAULT; > + > + /* Check the start address: needs to be page-aligned.. */ Why? The comment should tell me this. > + if (args.offset & ~PAGE_CACHE_MASK) > + return -EINVAL; > + > + if ((args.vec_size % sizeof(struct metadata_incore_ent)) != 0) > + return -EINVAL; > + > + if (!access_ok(VERIFY_WRITE, args.vec_addr, args.vec_size)) Seems unneccessary - copy_to_user() checks this. > + return -EFAULT; > + > + offset = args.offset; > + > + ent.unused = 0; > + vec_addr = args.vec_addr; > + > + while (vec_addr < args.vec_addr + args.vec_size) { > + if (signal_pending(current)) > + return -EINTR; > + cond_resched(); > + > + if (sb->s_op->metadata_incore(sb, &offset, &size) < 0) > + break; > + /* A merge or offset == 0 */ > + if (offset == last_offset + last_size) { > + last_size += size; > + offset = offset + size; > + continue; > + } > + ent.offset = last_offset; > + ent.size = last_size; > + if (copy_to_user((void *)(long)vec_addr, &ent, sizeof(ent))) > + return -EFAULT; > + vec_addr += sizeof(ent); > + entries++; > + > + last_offset = offset; > + last_size = size; > + ent.unused = 0; > + offset = offset + size; > + } > + > + if (last_size > 0 && vec_addr < args.vec_addr + args.vec_size) { > + ent.offset = last_offset; > + ent.size = last_size; > + if (copy_to_user((void *)(long)vec_addr, &ent, sizeof(ent))) > + return -EFAULT; > + entries++; > + } > + > + return entries; > +} > + > +/* > * When you add any new common ioctls to the switches above and below > * please update compat_sys_ioctl() too. > * > > ... > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
