freebsd-nq

History

Alfred Perlstein 426da3bcfb SMP Lock struct file, filedesc and the global file list.

Seigo Tanimura (tanimura) posted the initial delta.

I've polished it quite a bit reducing the need for locking and
adapting it for KSE.

Locks:

1 mutex in each filedesc
   protects all the fields.
   protects "struct file" initialization, while a struct file
     is being changed from &badfileops -> &pipeops or something
     the filedesc should be locked.

1 mutex in each struct file
   protects the refcount fields.
   doesn't protect anything else.
   the flags used for garbage collection have been moved to
     f_gcflag which was the FILLER short, this doesn't need
     locking because the garbage collection is a single threaded
     container.
  could likely be made to use a pool mutex.

1 sx lock for the global filelist.

struct file *	fhold(struct file *fp);
        /* increments reference count on a file */

struct file *	fhold_locked(struct file *fp);
        /* like fhold but expects file to locked */

struct file *	ffind_hold(struct thread *, int fd);
        /* finds the struct file in thread, adds one reference and
                returns it unlocked */

struct file *	ffind_lock(struct thread *, int fd);
        /* ffind_hold, but returns file locked */

I still have to smp-safe the fget cruft, I'll get to that asap.

2002-01-13 11:58:06 +00:00

ffs_alloc.c

SMP Lock struct file, filedesc and the global file list.

2002-01-13 11:58:06 +00:00

ffs_balloc.c

KSE Milestone 2

2001-09-12 08:38:13 +00:00

ffs_extern.h

KSE Milestone 2

2001-09-12 08:38:13 +00:00

ffs_inode.c

When a file is partially truncated, we first check to see if the

2001-12-13 05:07:48 +00:00

ffs_snapshot.c

Change the atomic_set_char to atomic_set_int and atomic_clear_char

2001-12-18 18:05:17 +00:00

ffs_softdep_stub.c

KSE Milestone 2

2001-09-12 08:38:13 +00:00

ffs_softdep.c

When going to sleep, we must save our SPL so that it does not get

2002-01-12 20:57:36 +00:00

ffs_subr.c

Remove blatantly pointless call to VOP_BMAP().

2001-05-01 09:12:31 +00:00

ffs_tables.c

…

ffs_vfsops.c

Fix a BUF_TIMELOCK race against BUF_LOCK and fix a deadlock in vget()

2001-12-20 22:42:27 +00:00

ffs_vnops.c

KSE Milestone 2

2001-09-12 08:38:13 +00:00

fs.h

Change the atomic_set_char to atomic_set_int and atomic_clear_char

2001-12-18 18:05:17 +00:00

README.snapshot

Update to describe use of mdconfig instead of deprecated vnconfig.

2001-04-14 18:32:09 +00:00

README.softupdates

Update to reflect current status.

2000-07-08 02:31:21 +00:00

softdep.h

When a new block is allocated to a directory, an fsync of a file

2001-05-17 07:24:03 +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