If you say Y here, you will be able to set per user limits for disk
usage (also called disk quotas). Currently, it works for the
ext2, ext3, ext4, jfs, ocfs2 and reiserfs file systems.
Note that gfs2 and xfs use their own quota system.
Ext3, ext4 and reiserfs also support journaled quotas for which
you don't need to run quotacheck(8) after an unclean shutdown.
For further details, read the Quota mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>, or the documentation provided
with the quota tools. Probably the quota support is only useful for
multi user systems. If unsure, say N.

source code:

fs/quota/dquot.c