freebsd

mirror of https://git.FreeBSD.org/src.git synced 2024-12-19 10:53:58 +00:00

History

Pawel Jakub Dawidek 39cfb23935 Fix ACLs handling for the root file system. Without this fix, when ACLs are set via tunefs(8) on the root file system, they are removed on boot when 'mount -a' is called, because mount(8) called for the root file system always add MNT_UPDATE flag and MNT_UPDATE flag isn't perfect. Now, one cannot remove ACLs stored in superblock (configured with tunefs(8)) via 'mount -a' nor 'mount -u -o noacls <file system>', but it is still possible to mount file system which doesn't have ACLs in superblock via 'mount -o acls <file system>' or /etc/fstab's 'acls' option. Reported by: Lech Lorens/pl.comp.os.bsd Discussed with: phk, rwatson Reviewed by: rwatson MFC after: 2 weeks		2005-01-15 17:09:53 +00:00
..
ffs_alloc.c	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
ffs_balloc.c	Remove the unused credential argument from VOP_FSYNC() and VFS_SYNC().	2005-01-11 07:36:22 +00:00
ffs_extern.h	Back when VOP_* was introduced, we did not have new-style struct	2004-12-01 23:16:38 +00:00
ffs_inode.c	Eliminate unused and unnecessary "cred" argument from vinvalbuf()	2005-01-14 07:33:51 +00:00
ffs_rawread.c	Wrap the bufobj operations in macros: BO_STRATEGY() and BO_WRITE()	2005-01-11 09:10:46 +00:00
ffs_snapshot.c	Remove the unused credential argument from VOP_FSYNC() and VFS_SYNC().	2005-01-11 07:36:22 +00:00
ffs_softdep_stub.c	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
ffs_softdep.c	Remove the unused credential argument from VOP_FSYNC() and VFS_SYNC().	2005-01-11 07:36:22 +00:00
ffs_subr.c	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
ffs_tables.c	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
ffs_vfsops.c	Fix ACLs handling for the root file system.	2005-01-15 17:09:53 +00:00
ffs_vnops.c	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
fs.h	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00
README.snapshot
README.softupdates
softdep.h	/* -> /*- for license, minor formatting changes	2005-01-07 02:29:27 +00:00

README.softupdates

$FreeBSD$

Using Soft Updates

To enable the soft updates feature in your kernel, add option
SOFTUPDATES to your kernel configuration.

Once you are running a kernel with soft update support, you need to enable
it for whichever filesystems you wish to run with the soft update policy.
This is done with the -n option to tunefs(8) on the UNMOUNTED filesystems,
e.g. from single-user mode you'd do something like:

	tunefs -n enable /usr

To permanently enable soft updates on the /usr filesystem (or at least
until a corresponding ``tunefs -n disable'' is done).


Soft Updates Copyright Restrictions

As of June 2000 the restrictive copyright has been removed and 
replaced with a `Berkeley-style' copyright. The files implementing
soft updates now reside in the sys/ufs/ffs directory and are
compiled into the generic kernel by default.


Soft Updates Status

The soft updates code has been running in production on many
systems for the past two years generally quite successfully.
The two current sets of shortcomings are:

1) On filesystems that are chronically full, the two minute lag
   from the time a file is deleted until its free space shows up
   will result in premature filesystem full failures. This
   failure mode is most evident in small filesystems such as
   the root. For this reason, use of soft updates is not
   recommended on the root filesystem.

2) If your system routines runs parallel processes each of which
   remove many files, the kernel memory rate limiting code may
   not be able to slow removal operations to a level sustainable
   by the disk subsystem. The result is that the kernel runs out
   of memory and hangs.

Both of these problems are being addressed, but have not yet
been resolved. There are no other known problems at this time.


How Soft Updates Work

For more general information on soft updates, please see:
	http://www.mckusick.com/softdep/
	http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/

--
Marshall Kirk McKusick <mckusick@mckusick.com>
July 2000