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History log of /src/sys/ufs/lfs/TODO
RevisionDateAuthorComments
 1.10  11-Dec-2005  christos merge ktrace-lwp.
 1.9  01-Apr-2005  perseant branches: 1.9.2;
Protect various per-fs structures with fs->lfs_interlock simple_lock, to
improve behavior in the multiprocessor case. Add debugging segment-lock
assertion statements.
 1.8  26-Feb-2005  perseant branches: 1.8.2;
Various minor LFS improvements:

* Note when lfs_putpages(9) thinks it is not going to be writing any
pages before calling genfs_putpages(9). This prevents a situation in
which blocks can be queued for writing without a segment header.
* Correct computation of NRESERVE(), though it is still a gross
overestimate in most cases. Note that if NRESERVE() is too high, it
may be impossible to create files on the filesystem. We catch this
case on filesystem mount and refuse to mount r/w.
* Allow filesystems to be mounted whose block size is == MAXBSIZE.
* Somewhere along the line, ufs_bmaparray(9) started mangling UNWRITTEN
entries in indirect blocks again, triggering a failed assertion "daddr
<= LFS_MAX_DADDR". Explicitly convert to and from int32_t to correct
this.
* Add a high-water mark for the number of dirty pages any given LFS can
hold before triggering a flush. This is settable by sysctl, but off
(zero) by default.
* Be more careful about the MAX_BYTES and MAX_BUFS computations so we
shouldn't see "please increase to at least zero" messages.
* Note that VBLK and VCHR vnodes can have nonzero values in di_db[0]
even though their v_size == 0. Don't panic when we see this.
* Change lfs_bfree to a signed quantity. The manner in which it is
processed before being passed to the cleaner means that sometimes it
may drop below zero, and the cleaner must be aware of this.
* Never report bfree < 0 (or higher than lfs_dsize) through
lfs_statvfs(9). This prevents df(1) from ever telling us that our full
filesystems have 16TB free.
* Account space allocated through lfs_balloc(9) that does not have
associated buffer headers, so that the pagedaemon doesn't run us out
of segments.
* Return ENOSPC from lfs_balloc(9) when bfree drops to zero.
* Address a deadlock in lfs_bmapv/lfs_markv when the filesystem is being
unmounted. Because vfs_busy() is a shared lock, and
lfs_bmapv/lfs_markv mark the filesystem vfs_busy(), the cleaner can be
holding the lock that umount() is blocking on, then try to vfs_busy()
again in getnewvnode().
 1.7  23-Feb-2003  perseant branches: 1.7.2; 1.7.8; 1.7.10; 1.7.12;
Fix a buffer overflow bug in the LFS_UBC case that manifested itself
either as a mysterious UVM error or as "panic: dirty bufs". Verify
maximum size in lfs_malloc.

Teach lfs_updatemeta and lfs_shellsort about oversized cluster blocks from
lfs_gop_write.

When unwiring pages in lfs_gop_write, deactivate them, under the theory
that the pagedaemon wanted to free them last we knew.
 1.6  17-Feb-2003  perseant Add code to UBCify LFS. This is still behind "#ifdef LFS_UBC" for now
(there are still some details to work out) but expect that to go
away soon. To support these basic changes (creation of lfs_putpages,
lfs_gop_write, mods to lfs_balloc) several other changes were made, to
wit:

* Create a writer daemon kernel thread whose purpose is to handle page
writes for the pagedaemon, but which also takes over some of the
functions of lfs_check(). This thread is started the first time an
LFS is mounted.

* Add a "flags" parameter to GOP_SIZE. Current values are
GOP_SIZE_READ, meaning that the call should return the size of the
in-core version of the file, and GOP_SIZE_WRITE, meaning that it
should return the on-disk size. One of GOP_SIZE_READ or
GOP_SIZE_WRITE must be specified.

* Instead of using malloc(...M_WAITOK) for everything, reserve enough
resources to get by and use malloc(...M_NOWAIT), using the reserves if
necessary. Use the pool subsystem for structures small enough that
this is feasible. This also obsoletes LFS_THROTTLE.

And a few that are not strictly necessary:

* Moves the LFS inode extensions off onto a separately allocated
structure; getting closer to LFS as an LKM. "Welcome to 1.6O."

* Unified GOP_ALLOC between FFS and LFS.

* Update LFS copyright headers to correct values.

* Actually cast to unsigned in lfs_shellsort, like the comment says.

* Keep track of which segments were empty before the previous
checkpoint; any segments that pass two checkpoints both dirty and
empty can be summarily cleaned. Do this. Right now lfs_segclean
still works, but this should be turned into an effectless
compatibility syscall.
 1.5  13-Jul-2001  perseant Merge the short-lived perseant-lfsv2 branch into the trunk.

Kernels and tools understand both v1 and v2 filesystems; newfs_lfs
generates v2 by default. Changes for the v2 layout include:

- Segments of non-PO2 size and arbitrary block offset, so these can be
matched to convenient physical characteristics of the partition (e.g.,
stripe or track size and offset).

- Address by fragment instead of by disk sector, paving the way for
non-512-byte-sector devices. In theory fragments can be as large
as you like, though in reality they must be smaller than MAXBSIZE in size.

- Use serial number and filesystem identifier to ensure that roll-forward
doesn't get old data and think it's new. Roll-forward is enabled for
v2 filesystems, though not for v1 filesystems by default.

- The inode free list is now a tailq, paving the way for undelete (undelete
is not yet implemented, but can be without further non-backwards-compatible
changes to disk structures).

- Inode atime information is kept in the Ifile, instead of on the inode;
that is, the inode is never written *just* because atime was changed.
Because of this the inodes remain near the file data on the disk, rather
than wandering all over as the disk is read repeatedly. This speeds up
repeated reads by a small but noticeable amount.

Other changes of note include:

- The ifile written by newfs_lfs can now be of arbitrary length, it is no
longer restricted to a single indirect block.

- Fixed an old bug where ctime was changed every time a vnode was created.
I need to look more closely to make sure that the times are only updated
during write(2) and friends, not after-the-fact during a segment write,
and certainly not by the cleaner.
 1.4  17-Nov-2000  perseant branches: 1.4.2; 1.4.4; 1.4.6;
Correct accounting of lfs_avail, locked_queue_count, and locked_queue_bytes.
(PR #11468). In the case of fragment allocation, check to see if enough
space is available before extending a fragment already scheduled for writing.

The locked_queue_* variables indicate the number of buffer headers and bytes,
respectively, that are unavailable to getnewbuf() because they are locked up
waiting for LFS to flush them; make sure that that is actually what we're
counting, i.e., never count malloced buffers, and always use b_bufsize instead
of b_bcount.

If DEBUG is defined, the periodic calls to lfs_countlocked will now complain
if either counter is incorrect. (In the future lfs_countlocked will not need
to be called at all if DEBUG is not defined.)
 1.3  15-Mar-1999  perseant branches: 1.3.8;
New CHANGES files that describes briefly all nontrivial changes made to
the LFS since the 4.4lite2 code was merged into NetBSD.

TODO updated to remove everything marked DONE in 4.4, and add in a list
of more current things to do.

Get rid of comments about the cleaner syscall code and missing fragment
support from README.
 1.2  29-Jun-1994  cgd New RCS ID's, take two. they're more aesthecially pleasant, and use 'NetBSD'
 1.1  08-Jun-1994  mycroft branches: 1.1.1;
Update to 4.4-Lite fs code, with local changes.
 1.1.1.1  01-Mar-1998  fvdl Import 4.4BSD-Lite for reference
 1.3.8.1  22-Nov-2000  bouyer Sync with HEAD.
 1.4.6.1  03-Aug-2001  lukem update to -current
 1.4.4.1  27-Jun-2001  perseant Import of what I've been calling "LFSv2", that is, LFS with some features
added that require changes to the on-disk data structures. These include:

- 64-bit time in everything but inodes
- User-specified segment offset, and segment size no longer
restricted to PO2.
- Serial number on segment summaries in addition to timestamp, and
a new volume identifier, to make roll-forward feasible without
fear of finding old data and thinking it was new.

Although I think this version works at least as well as what's on the trunk,
we're not done yet; hence this commit is going in on a branch and not on
the trunk. Enhancements that are not here yet include fragment addressing,
like FFS does, instead of block addressing.
 1.4.2.1  24-Aug-2001  nathanw Catch up with -current.
 1.7.12.1  19-Mar-2005  yamt sync with head. xen and whitespace. xen part is not finished.
 1.7.10.1  29-Apr-2005  kent sync with -current
 1.7.8.1  10-May-2005  riz Pull up the following revisions (requested by perseant in ticket #1281):

1.8 sys/ufs/lfs/TODO
1.75 sys/ufs/lfs/lfs.h (via patch)
1.74 sys/ufs/lfs/lfs_alloc.c (via patch)
1.49, 1.51 sys/ufs/lfs/lfs_balloc.c (1.51 via patch)
1.78 sys/ufs/lfs/lfs_bio.c
1.62 sys/ufs/lfs/lfs_extern.h (via patch)
1.156 sys/ufs/lfs/lfs_segment.c (via patch)
1.48 sys/ufs/lfs/lfs_subr.c
1.101 sys/ufs/lfs/lfs_syscalls.c
1.163 sys/ufs/lfs/lfs_vfsops.c (via patch)
1.134 sys/ufs/lfs/lfs_vnops.c (via patch)
1.61 sys/ufs/ufs/ufs_readwrite.c (via patch)

1.20 libexec/lfs_cleanerd/clean.h (via patch)
1.52 libexec/lfs_cleanerd/cleanerd.c (via patch)
1.41 libexec/lfs_cleanerd/library.c (via patch)

1.4 regress/sys/fs/lfs/newfs_fsck/Makefile
1.2 regress/sys/fs/lfs/newfs_fsck/mkfs_mount
1.2 regress/sys/fs/lfs/newfs_fsck/smallfiles
1.3 sbin/fsck_lfs/bufcache.c
1.3 sbin/fsck_lfs/bufcache.h
1.3 sbin/fsck_lfs/lfs.h
1.8 sbin/fsck_lfs/lfs.c (via patch)
1.8 sbin/fsck_lfs/pass3.c (via patch)
1.18 sbin/fsck_lfs/pass0.c (via patch)
1.18 sbin/fsck_lfs/utilities.c (via patch)
1.7 sbin/fsck_lfs/segwrite.c
1.19 sbin/fsck_lfs/setup.c (via patch)
1.3 sbin/newfs_lfs/Makefile
0 sbin/newfs_lfs/lfs.c (yes, remove it)
1.1 sbin/newfs_lfs/make_lfs.c
1.15 sbin/newfs_lfs/newfs.c (via patch)

Various minor LFS improvements.

Kernel:

* Note when lfs_putpages(9) thinks it is not going to be writing any
pages before calling genfs_putpages(9). This prevents a situation in
which blocks can be queued for writing without a segment header.
* Correct computation of NRESERVE(), though it is still a gross
overestimate in most cases. Note that if NRESERVE() is too high, it
may be impossible to create files on the filesystem. We catch this
case on filesystem mount and refuse to mount r/w.
* Allow filesystems to be mounted whose block size is == MAXBSIZE.
* Somewhere along the line, ufs_bmaparray(9) started mangling UNWRITTEN
entries in indirect blocks again, triggering a failed assertion "daddr
<= LFS_MAX_DADDR". Explicitly convert to and from int32_t to correct
this. Should fix PR #29045.
* Add a high-water mark for the number of dirty pages any given LFS can
hold before triggering a flush. This is settable by sysctl, but off
(zero) by default.
* Be more careful about the MAX_BYTES and MAX_BUFS computations so we
shouldn't see "please increase to at least zero" messages.
* Note that VBLK and VCHR vnodes can have nonzero values in di_db[0]
even though their v_size == 0. Don't panic when we see this.
Fixes PR #26680.
* Change lfs_bfree to a signed quantity. The manner in which it is
processed before being passed to the cleaner means that sometimes it
may drop below zero, and the cleaner must be aware of this.
* Never report bfree < 0 (or higher than lfs_dsize) through
lfs_statfs(9). This prevents df(1) from ever telling us that our full
filesystems have 16TB free.
* Account space allocated through lfs_balloc(9) that does not have
associated buffer headers, so that the pagedaemon doesn't run us out
of segments.
* Return ENOSPC from lfs_balloc(9) when bfree drops to zero.
* Address a deadlock in lfs_bmapv/lfs_markv when the filesystem is being
unmounted. Because vfs_busy() is a shared lock, and
lfs_bmapv/lfs_markv mark the filesystem vfs_busy(), the cleaner can be
holding the lock that umount() is blocking on, then try to vfs_busy()
again in getnewvnode().

cleaner:

* Adapt lfs_cleanerd to use the fcntl call to get the Ifile filehandle,
so it need not be in the namespace.
* Make lfs_cleanerd be more careful when there are very few available
segments.
* Make lfs_cleanerd less verbose when the filesystem is unmounted.

newfs_lfs, fsck_lfs, and regression:

* Extend the lfs library from fsck_lfs(8) so that it can be used with a
not-yet-existent LFS. Make newfs_lfs(8) use this library, so it can
create LFSs whose Ifile is larger than one segment. Addresses PR #11110.
* Make newfs_lfs(8) use strsuftoi64() for its arguments, a la newfs(8).
* Make fsck_lfs(8) respect the "file system is clean" flag.
* Don't let fsck_lfs(8) think it has dirty blocks when invoked with the
-n flag.
* Remove the Ifile from the filesystem namespace. The cleaner now uses
a fcntl call on the root inode to find the Ifile filehandle. (As a
side-effect, addresses PR #29144.)
 1.7.2.2  10-Nov-2005  skrll Sync with HEAD. Here we go again...
 1.7.2.1  04-Mar-2005  skrll Sync with HEAD.

Hi Perry!
 1.8.2.1  07-May-2005  tron Apply patch (requested by perseant in ticket #242):
* fsck_lfs buffer cache fixes, including PR #29151
* Change fsck_lfs phase 0 message to reflect reality
* fsck_lfs: check phase 5 (cleanerinfo accounting) even on
roll-forward
* Keep better track of the free list during roll-forward, avoiding
a core dump
* Improve hash table use for fsck_lfs buffer and vnode cache
* Document fsck_lfs flag -f, and implement -q
* Add resize_lfs, including kernel support
* Add LFS to mountd's list of exportable filesystem types
* Make the LFS lkm work again [christos@]
* Add MP locking to the LFS kernel subsystem
* Fix pager_map deadlock in lfs_putpages()
* Avoid incomplete file extension that looks like "partial
truncation" to fsck
* Use lfs_malloc for cleaner malloc, since the cleaner often runs
in low-memory conditions.
* Use splay trees, not hash table, to track page allocation for
write.
* Fix mkdir panic on full fs
* Fix page accounting leak by counting differently.
* Use rightly named structure for lfs_getattr [skrll@]
* Cosmetic changes for readability.
 1.9.2.1  21-Jun-2006  yamt sync with head.

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