enough to be useful, and broadening it so that it did would have meant
that operations possibly requiring synchronous disk activity would have
to be done in splbio(). This clearly was not going to work.
Worked around this in the LFS case by having lfs_cluster_callback put an
extra hold on the vnode before calling biodone(), and taking the hold
off without HOLDRELE's problematic list swapping. lfs_vunref() will take
care of that---in thread context---on the next write if need be.
Also, ensure that the list walking in lfs_{writevnodes,segunlock,gather}
takes into account the possibility that the list may change
underneath it (possibly because it itself deleted an element).
Tested on i386, test-compiled on alpha.
I found while making sure there weren't any new ones.
* Make the write clusters keep track of the buffers whose blocks they contain.
This should make it possible to (1) write clusters using a page mapping
instead of malloc, if desired, and (2) schedule blocks for rewriting
(somewhere else) if a write error occurs. Code is present to use
pagemove() to construct the clusters but that is untested and will go away
anyway in favor of page mapping.
* DEBUG now keeps a log of Ifile writes, so that any lingering instances of
the "dirty bufs" problem can be properly debugged.
* Keep track of whether the Ifile has been dirtied by various routines that
can be called by lfs_segwrite, and loop on that until it is clean, for
a checkpoint. Checkpoints need to be squeaky clean.
* Warn the user (once) if the Ifile grows larger than is reasonable for their
buffer cache. Both lfs_mountfs and lfs_unmount check since the Ifile can
grow.
* If an inode is not found in a disk block, try rereading the block, under
the assumption that the block was copied to a cluster and then freed.
* Protect WRITEINPROG() with splbio() to fix a hang in lfs_update.
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.
Kernel:
* Add runtime quantity lfs_ravail, the number of disk-blocks reserved
for writing. Writes to the filesystem first reserve a maximum amount
of blocks before their write is allowed to proceed; after the blocks
are allocated the reserved total is reduced by a corresponding amount.
If the lfs_reserve function cannot immediately reserve the requested
number of blocks, the inode is unlocked, and the thread sleeps until
the cleaner has made enough space available for the blocks to be
reserved. In this way large files can be written to the filesystem
(or, smaller files can be written to a nearly-full but thoroughly
clean filesystem) and the cleaner can still function properly.
* Remove explicit switching on dlfs_minfreeseg from the kernel code; it
is now merely a fs-creation parameter used to compute dlfs_avail and
dlfs_bfree (and used by fsck_lfs(8) to check their accuracy). Its
former role is better assumed by a properly computed dlfs_avail.
* Bounds-check inode numbers submitted through lfs_bmapv and lfs_markv.
This prevents a panic, but, if the cleaner is feeding the filesystem
the wrong data, you are still in a world of hurt.
* Cleanup: remove explicit references of DEV_BSIZE in favor of
btodb()/dbtob().
lfs_cleanerd:
* Make -n mean "send N segments' blocks through a single call to
lfs_markv". Previously it had meant "clean N segments though N calls
to lfs_markv, before looking again to see if more need to be cleaned".
The new behavior gives better packing of direct data on disk with as
little metadata as possible, largely alleviating the problem that the
cleaner can consume more disk through inefficient use of metadata than
it frees by moving dirty data away from clean "holes" to produce
entirely clean segments.
* Make -b mean "read as many segments as necessary to write N segments
of dirty data back to disk", rather than its former meaning of "read
as many segments as necessary to free N segments worth of space". The
new meaning, combined with the new -n behavior described above,
further aids in cleaning storage efficiency as entire segments can be
written at once, using as few blocks as possible for segment summaries
and inode blocks.
* Make the cleaner take note of segments which could not be cleaned due
to error, and not attempt to clean them until they are entirely free
of dirty blocks. This prevents the case in which a cleanerd running
with -n 1 and without -b (formerly the default) would spin trying
repeatedly to clean a corrupt segment, while the remaining space
filled and deadlocked the filesystem.
* Update the lfs_cleanerd manual page to describe all the options,
including the changes mentioned here (in particular, the -b and -n
flags were previously undocumented).
fsck_lfs:
* Check, and optionally fix, lfs_avail (to an exact figure) and
lfs_bfree (within a margin of error) in pass 5.
newfs_lfs:
* Reduce the default dlfs_minfreeseg to 1/20 of the total segments.
* Add a warning if the sgs disklabel field is 16 (the default for FFS'
cpg, but not usually desirable for LFS' sgs: 5--8 is a better range).
* Change the calculation of lfs_avail and lfs_bfree, corresponding to
the kernel changes mentioned above.
mount_lfs:
* Add -N and -b options to pass corresponding -n and -b options to
lfs_cleanerd.
* Default to calling lfs_cleanerd with "-b -n 4".
[All of these changes were largely tested in the 1.5 branch, with the
idea that they (along with previous un-pulled-up work) could be applied
to the branch while it was still in ALPHA2; however my test system has
experienced corruption on another filesystem (/dev/console has gone
missing :^), and, while I believe this unrelated to the LFS changes, I
cannot with good conscience request that the changes be pulled up.]
Change the space computation to appear to change the size of the *disk*
rather than the *bytes used* when more segment summaries and inode
blocks are written. Try to estimate the amount of space that these will
take up when more files are written, so the disk size doesn't change too
much.
Regularize error returns from lfs_valloc, lfs_balloc, lfs_truncate: they
now fail entirely, rather than succeeding half-way and leaving the fs in
an inconsistent state.
Rewrite lfs_truncate, mostly stealing from ffs_truncate. The old
lfs_truncate had difficulty truncating a large file to a non-zero size
(indirect blocks were not handled appropriately).
Unmark VDIROP on fvp after ufs_remove, ufs_rmdir, so these can be
reclaimed immediately: this vnode would not be written to disk again
anyway if the removal succeeded, and if it failed, no directory
operation occurred.
ufs_makeinode and ufs_mkdir now remove IN_ADIROP on error.
buffer cache flags, to marking the inode and/or indirect blocks with a
special disk address UNWRITTEN==-2 when a block is accounted for. (This
address is never written to disk, but only used in-core. This is essentially
the same method of block accounting as on the UBC branch, where the buffer
headers don't exist.) Make sure that truncation is handled properly,
especially in the case of holey files.
Fixes PR#9994.
1.4 branch.
* Use a separate per-fs lock, instead of ufs_hashlock, to protect the Inode
free list. This seems to prevent the "lockmgr: %d, not exclusive lock holder
%d, unlocking" message I was mis-attributing last night to an unlocked vnode
being passed to vrele.
* Change calling semantics of lfs_ifind, to give better error reporting:
If fed a struct buf, it can report the block number of the offending inode
block as well as the inode number.
* Back out rev 1.10 of lfs_subr.c, since the replacement code was slightly
uglier while being functionally identical.
* Make lfs_vunref use the same free list convention as vrele/vput, so that
vget does not remove vnodes from a hash list they are not on.
from being inactivated under some conditions. Removed vnodes are now
inactivated when the VDIROP flag is cleared, and to prevent block
accounting problems this clearing has been postponed until
lfs_segunlock.
include:
- DIROP segregation is enabled, and greater care is taken
to make sure that a checkpoint completes. Fsck is not
needed to remount the filesystem.
- Several checks to make sure that the LFS subsystem does not
overuse various resources (memory, in particular).
- The cleaner routines, lfs_markv in particular, are completely
rewritten. A buffer overflow is removed. Greater care is taken
to ensure that inodes come from where lfs_cleanerd say they come
from (so we know nothing has changed since lfs_bmapv was called).
- Fragment allocation is fixed, so that writes beyond end-of-file
do the right thing.
perseant