need for most calls to vm_page_busy(). Specifically, most calls to
vm_page_busy() occur immediately prior to a call to vm_page_remove().
In such cases, the containing vm object is locked across both calls.
Consequently, the setting of the vm page's PG_BUSY flag is not even
visible to other threads that are following the synchronization
protocol.
This change (1) eliminates the calls to vm_page_busy() that
immediately precede a call to vm_page_remove() or functions, such as
vm_page_free() and vm_page_rename(), that call it and (2) relaxes the
requirement in vm_page_remove() that the vm page's PG_BUSY flag is
set. Now, the vm page's PG_BUSY flag is set only when the vm object
lock is released while the vm page is still in transition. Typically,
this is when it is undergoing I/O.
buf->b-dev.
Put a bio between the buf passed to dev_strategy() and the device driver
strategy routine in order to not clobber fields in the buf.
Assert copyright on vfs_bio.c and update copyright message to canonical
text. There is no legal difference between John Dysons two-clause
abbreviated BSD license and the canonical text.
Give ffs it's own bufobj->bo_ops vector and create a private strategy
routine, (currently misnamed for forwards compatibility), which is
just a copy of the generic bufstrategy routine except we call
softdep_disk_prewrite() directly instead of through the buf_prewrite()
indirection.
Teach UFS about the need for softdep_disk_prewrite() and call the
function directly in FFS.
Remove buf_prewrite() from the default bufstrategy() and from the
global bio_ops method vector.
We keep si_bsize_phys around for now as that is the simplest way to pull
the number out of disk device drivers in devfs_open(). The correct solution
would be to do an ioctl(DIOCGSECTORSIZE), but the point is probably mooth
when filesystems sit on GEOM, so don't bother for now.
and release of the global page queues lock required to make the call.
Remove GIANT_REQUIRED from vm_hold_free_pages(). All of its VM operations
are properly synchronized.
Extend it with a strategy method.
Add bufstrategy() which do the usual VOP_SPECSTRATEGY/VOP_STRATEGY
song and dance.
Rename ibwrite to bufwrite().
Move the two NFS buf_ops to more sensible places, add bufstrategy
to them.
Add inlines for bwrite() and bstrategy() which calls through
buf->b_bufobj->b_ops->b_{write,strategy}().
Replace almost all VOP_STRATEGY()/VOP_SPECSTRATEGY() calls with bstrategy().
Initialize b_bufobj for all buffers.
Make incore() and gbincore() take a bufobj instead of a vnode.
Make inmem() local to vfs_bio.c
Change a lot of VI_[UN]LOCK(bp->b_vp) to BO_[UN]LOCK(bp->b_bufobj)
also VI_MTX() to BO_MTX(),
Make buf_vlist_add() take a bufobj instead of a vnode.
Eliminate other uses of bp->b_vp where bp->b_bufobj will do.
Various minor polishing: remove "register", turn panic into KASSERT,
use new function declarations, TAILQ_FOREACH_SAFE() etc.
Add bufobj_wref(), bufobj_wdrop() and bufobj_wwait() to handle the write
count on a bufobj. Bufobj_wdrop() replaces vwakeup().
Use these functions all relevant places except in ffs_softdep.c where
the use if interlocked_sleep() makes this impossible.
Rename b_vnbufs to b_bobufs now that we touch all the relevant files anyway.
of the number of threads which are inside whatever is behind the
cdevsw for this particular cdev.
Make the device mutex visible through dev_lock() and dev_unlock().
We may want finer granularity later.
Replace spechash_mtx use with dev_lock()/dev_unlock().
preparation for integration of p4::phk_bufwork. In the future,
local filesystems will talk to GEOM directly and they will consequently
be able to issue BIO_DELETE directly. Since the removal of the fla
driver, BIO_DELETE has effectively been a no-op anyway.
When avoiding the zeroing of "bogus_page" when it appears in a buf,
be sure to advance the pointers into the data for successive pages.
The bug caused file corruption when read(2)ing from a "hole" in a
file where a previous page of the read block had already been faulted
in: fsx tripped up on this pretty quickly. The particular access
pattern is probably pretty unusual, so other applications probably
wouldn't have had problems, but you'd never know.
Reviewed By: alc@
around in the vnodes surroundings when we allocate a block.
Assign a blocksize when we create a vnode, and yell a warning (and ignore it)
if we got the wrong size.
Please email all such warnings to me.
The big lines are:
NODEV -> NULL
NOUDEV -> NODEV
udev_t -> dev_t
udev2dev() -> findcdev()
Various minor adjustments including handling of userland access to kernel
space struct cdev etc.
allocation and deallocation. This flag's principal use is shortly after
allocation. For such cases, clearing the flag is pointless. The only
unusual use of PG_ZERO is in vfs_bio_clrbuf(). However, allocbuf() never
requests a prezeroed page. So, vfs_bio_clrbuf() never sees a prezeroed
page.
Reviewed by: tegge@
silences an annoying warning in getblk() when VMIO'ing on a directory
vnode, which can happen when vfs.vmiodirenable is 1.
Bring the warning message in line with reality at the same time.
Submitted by: hmp
were a rather overwhelming task. I soon learned that if you don't know
where you're going to store something, at least try to pile it next to
something slightly related in the hope that a pattern emerges.
Apply the same principle to the ffs/snapshot/softupdates code which have
leaked into specfs: Add yet a buf-quasi-method and call it from the
only two places I can see it can make a difference and implement the
magic in ffs_softdep.c where it belongs.
It's not pretty, but at least it's one less layer violated.
This is what we came here for: Hang dev_t's from their cdevsw,
refcount cdevsw and dev_t and generally keep track of things a lot
better than we used to:
Hold a cdevsw reference around all entrances into the device driver,
this will be necessary to safely determine when we can unload driver
code.
Hold a dev_t reference while the device is open.
KASSERT that we do not enter the driver on a non-referenced dev_t.
Remove old D_NAG code, anonymous dev_t's are not a problem now.
When destroy_dev() is called on a referenced dev_t, move it to
dead_cdevsw's list. When the refcount drops, free it.
Check that cdevsw->d_version is correct. If not, set all methods
to the dead_*() methods to prevent entrance into driver. Print
warning on console to this effect. The device driver may still
explode if it is also incompatible with newbus, but in that case
we probably didn't get this far in the first place.
accurate reporting of multi-terabyte filesystem sizes.
You should build and boot a new kernel BEFORE doing a `make world'
as the new kernel will know about binaries using the old statfs
structure, but an old kernel will not know about the new system
calls that support the new statfs structure. Running an old kernel
after a `make world' will cause programs such as `df' that do a
statfs system call to fail with a bad system call.
Reviewed by: Bruce Evans <bde@zeta.org.au>
Reviewed by: Tim Robbins <tjr@freebsd.org>
Reviewed by: Julian Elischer <julian@elischer.org>
Reviewed by: the hoards of <arch@freebsd.org>
Sponsored by: DARPA & NAI Labs.
consistency initialized. Consequently, a number of conditionals that
checked the validity of b_object before passing it to VM_OBJECT_LOCK()
and VM_OBJECT_UNLOCK() are no longer needed.
waitrunningbufspace() calls so that they are always able to
proceed and clean up buffer space.
Submitted by: Brian Fundakowski Feldman <green@freebsd.org>
the point where it being a macro is no longer sensible, and it will
only be more so in days to come.
BIO_STRATEGY() is now only used from DEV_STRATEGY() and should not
be used directly anymore.
Put the contents of both in the new function dev_strategy() and
make DEV_STRATEGY() call that function.
In addition, this allows us to make the rather magic bufdonebio()
helper function static.
This alse saves hunderedandsome bytes of code in a typical kernel.
caused snapshot related problems.
- The vp can not be NULL here or we would panic in vfs_bio_awrite(). Stop
confusing the logic by checking for it in several places.
Submitted by: kirk and then rototilled by me to remove vp == NULL checks.
freed belong to the kernel object.)
- Increase the granularity of the vm object locking in vm_hold_load_pages()
in order to reduce the number of times that we acquire and release the
same lock.
pmap_extract_and_hold(). Note, however, that GIANT_REQUIRED should not be
removed until all platforms fully implement the "prot" parameter to
pmap_extract_and_hold().
Reviewed by: tegge
bail out if the buffer is not already present.
- The buffer returned by incore() is not locked and should not be sent to
brelse(). Use getblk() with the new GB_NOCREAT flag to preserve the
desired semantics.
- Surround all accesses of the BKGRD{WAIT,INPROG} flags with the vnode
interlock.
- Don't use the B_LOCKED flag and QUEUE_LOCKED for background write
buffers. Check for the BKGRDINPROG flag before recycling or throwing
away a buffer. We do this instead because it is not safe for us to move
the original buffer to a new queue from the callback on the background
write buffer.
- Remove the B_LOCKED flag and the locked buffer queue. They are no longer
used.
- The vnode interlock is used around checks for BKGRDINPROG where it may
not be strictly necessary. If we hold the buf lock the a back-ground
write will not be started without our knowledge, one may only be
completed while we're not looking. Rather than remove the code, Document
two of the places where this extra locking is done. A pass should be
done to verify and minimize the locking later.
where physical addresses larger than virtual addresses, such as i386s
with PAE.
- Use this to represent physical addresses in the MI vm system and in the
i386 pmap code. This also changes the paddr parameter to d_mmap_t.
- Fix printf formats to handle physical addresses >4G in the i386 memory
detection code, and due to kvtop returning vm_paddr_t instead of u_long.
Note that this is a name change only; vm_paddr_t is still the same as
vm_offset_t on all currently supported platforms.
Sponsored by: DARPA, Network Associates Laboratories
Discussed with: re, phk (cdevsw change)
- Create a new function bdone() which sets B_DONE and calls wakup(bp). This
is suitable for use as b_iodone for buf consumers who are not going
through the buf cache.
- Create a new function bwait() which waits for the buf to be done at a set
priority and with a specific wmesg.
- Replace several cases where the above functionality was implemented
without locking with the new functions.
requiring locked bufs in vfs_bio_awrite(). Previously the buf could
have been written out by fsync before we acquired the buf lock if it
weren't for giant. The cluster_wbuild() handles this race properly but
the single write at the end of vfs_bio_awrite() would not.
- Modify flushbufqueues() so there is only one copy of the loop. Pass a
parameter in that says whether or not we should sync bufs with deps.
- Call flushbufqueues() a second time and then break if we couldn't find
any bufs without deps.
- Define one flag GB_LOCK_NOWAIT that tells getblk() to pass the LK_NOWAIT
flag to the initial BUF_LOCK(). This will eventually be used in cases
were we want to use a buffer only if it is not currently in use.
- Convert all consumers of the getblk() api to use this extra parameter.
Reviwed by: arch
Not objected to by: mckusick
delta 1.371) we must ensure that we do not get ourselves into a
recursive trap endlessly trying to clean up after ourselves.
Reported by: Attila Nagy <bra@fsn.hu>
Sponsored by: DARPA & NAI Labs.
track of the number of dirty buffers held by a vnode. When a
bdwrite is done on a buffer, check the existing number of dirty
buffers associated with its vnode. If the number rises above
vfs.dirtybufthresh (currently 90% of vfs.hidirtybuffers), one
of the other (hopefully older) dirty buffers associated with
the vnode is written (using bawrite). In the event that this
approach fails to curb the growth in it the vnode's number of
dirty buffers (due to soft updates rollback dependencies),
the more drastic approach of doing a VOP_FSYNC on the vnode
is used. This code primarily affects very large and actively
written files such as snapshots. This change should eliminate
hanging when taking snapshots or doing background fsck on
very large filesystems.
Hopefully, one day it will be possible to cache filesystem
metadata in the VM cache as is done with file data. As it
stands, only the buffer cache can be used which limits total
metadata storage to about 20Mb no matter how much memory is
available on the system. This rather small memory gets badly
thrashed causing a lot of extra I/O. For example, taking a
snapshot of a 1Tb filesystem minimally requires about 35,000
write operations, but because of the cache thrashing (we only
have about 350 buffers at our disposal) ends up doing about
237,540 I/O's thus taking twenty-five minutes instead of four
if it could run entirely in the cache.
Reported by: Attila Nagy <bra@fsn.hu>
Sponsored by: DARPA & NAI Labs.
- Remove the buftimelock mutex and acquire the buf's interlock to protect
these fields instead.
- Hold the vnode interlock while locking bufs on the clean/dirty queues.
This reduces some cases from one BUF_LOCK with a LK_NOWAIT and another
BUF_LOCK with a LK_TIMEFAIL to a single lock.
Reviewed by: arch, mckusick
queue lock already held.
- In getblk() and flushbufqueues() use bremfreel() while we still have the
buf queue lock held to keep the lists consistent.
- Add LK_NOWAIT to two cases where we're essentially asserting that the bufs
are not locked while acquiring the locks. This will make sure that we get
the appropriate panic() and not another one for sleeping with a lock held.
that is protected by the vnode lock.
- Move B_SCANNED into b_vflags and call it BV_SCANNED.
- Create a vop_stdfsync() modeled after spec's sync.
- Replace spec_fsync, msdos_fsync, and hpfs_fsync with the stdfsync and some
fs specific processing. This gives all of these filesystems proper
behavior wrt MNT_WAIT/NOWAIT and the use of the B_SCANNED flag.
- Annotate the locking in buf.h
buf lists, synchronization variables, and atomic ops for the counters.
This change does not remove giant from any code although some pushdown
may be possible.
- In vfs_bio_awrite() don't access buf fields without the buf lock.
vm_pageout_deficit:
1. Update vm_pageout_deficit before VM_WAIT. There is no sense in
delaying the update; the sooner the pageout daemon receives this
information the better. Reviewed by: tegge
2. Update vm_pageout_deficit according to the number of pages still
needed to complete the allocation, not the original size of the
allocation. Submitted by: tegge
(These errors have existed since the introduction of vm_pageout_deficit
in revision 1.144.)
portable copy. Note that pmap_extract() must be used instead of
pmap_kextract().
This is precursor work to a reorganization of vmapbuf() to close remaining
user/kernel races (which can lead to a panic).
to sort out disk-io from file-io in the vm/buffer/filesystem space.
The intent is to sort VOP_STRATEGY calls into those which operate
on "real" vnodes and those which operate on VCHR vnodes. For
the latter kind, the call will be changed to VOP_SPECSTRATEGY,
possibly conditionally for those places where dual-use happens.
Add a default VOP_SPECSTRATEGY method which will call the normal
VOP_STRATEGY. First time it is called it will print debugging
information. This will only happen if a normal vnode is passed
to VOP_SPECSTRATEGY by mistake.
Add a real VOP_SPECSTRATEGY in specfs, which does what VOP_STRATEGY
does on a VCHR vnode today.
Add a new VOP_STRATEGY method in specfs to catch instances where
the conversion to VOP_SPECSTRATEGY has not yet happened. Handle
the request just like we always did, but first time called print
debugging information.
Apart up to two instances of console messages per boot, this amounts
to a glorified no-op commit.
If you get any of the messages on your console I would very much
like a copy of them mailed to phk@freebsd.org
they may be the only viable ones to flush. Thus it will now wait for
an inode lock if the other alternatives will result in rollbacks (and
immediate redirtying of the buffer). If only buffers with rollbacks
are available, one will be flushed, but then the buffer daemon will
wait briefly before proceeding. Failing to wait briefly effectively
deadlocks a uniprocessor since every other process writing to that
filesystem will wait for the buffer daemon to clean up which takes
close enough to forever to feel like a deadlock.
Reported by: Archie Cobbs <archie@dellroad.org>
Sponsored by: DARPA & NAI Labs.
Approved by: re
indirectly through vm_page_protect(). The one remaining page flag that
is updated by vm_page_protect() is already being updated by our various
pmap implementations.
Note: A later commit will similarly change the VM_PROT_READ case and
eliminate vm_page_protect().
to help clean up. After selecting a potential buffer to write, this
patch has it acquire a lock on the vnode that owns the buffer before
trying to write it. The vnode lock is necessary to avoid a race with
some other process holding the vnode locked and trying to flush its
dirty buffers. In particular, if the vnode in question is a snapshot
file, then the race can lead to a deadlock. To avoid slowing down the
buf_daemon, it does a non-blocking lock request when trying to lock
the vnode. If it fails to get the lock it skips over the buffer and
continues down its queue looking for buffers to flush.
Sponsored by: DARPA & NAI Labs.
v_tag is now const char * and should only be used for debugging.
Additionally:
1. All users of VT_NTS now check vfsconf->vf_type VFCF_NETWORK
2. The user of VT_PROCFS now checks for the new flag VV_PROCDEP, which
is propagated by pseudofs to all child vnodes if the fs sets PFS_PROCDEP.
Suggested by: phk
Reviewed by: bde, rwatson (earlier version)
Introduce biowait() function. Currently there is a race condition and the
mitigation is a timeout/retry. It is not obvious what kind of locking (if any)
is suitable for BIO_DONE, since the majority of users take are of this
themselves, and only a few places actually rely on the wakeup.
Sponsored by: DARPA & NAI Labs.
in the original hardwired sysctl implementation.
The buf size calculator still overflows an integer on machines with large
KVA (eg: ia64) where the number of pages does not fit into an int. Use
'long' there.
Change Maxmem and physmem and related variables to 'long', mostly for
completeness. Machines are not likely to overflow 'int' pages in the
near term, but then again, 640K ought to be enough for anybody. This
comes for free on 32 bit machines, so why not?
- v_vflag is protected by the vnode lock and is used when synchronization
with VOP calls is needed.
- v_iflag is protected by interlock and is used for dealing with vnode
management issues. These flags include X/O LOCK, FREE, DOOMED, etc.
- All accesses to v_iflag and v_vflag have either been locked or marked with
mp_fixme's.
- Many ASSERT_VOP_LOCKED calls have been added where the locking was not
clear.
- Many functions in vfs_subr.c were restructured to provide for stronger
locking.
Idea stolen from: BSD/OS
As this code is not actually used by any of the existing
interfaces, it seems unlikely to break anything (famous
last words).
The internal kernel interface to manipulate these attributes
is invoked using two new IO_ flags: IO_NORMAL and IO_EXT.
These flags may be specified in the ioflags word of VOP_READ,
VOP_WRITE, and VOP_TRUNCATE. Specifying IO_NORMAL means that
you want to do I/O to the normal data part of the file and
IO_EXT means that you want to do I/O to the extended attributes
part of the file. IO_NORMAL and IO_EXT are mutually exclusive
for VOP_READ and VOP_WRITE, but may be specified individually
or together in the case of VOP_TRUNCATE. For example, when
removing a file, VOP_TRUNCATE is called with both IO_NORMAL
and IO_EXT set. For backward compatibility, if neither IO_NORMAL
nor IO_EXT is set, then IO_NORMAL is assumed.
Note that the BA_ and IO_ flags have been `merged' so that they
may both be used in the same flags word. This merger is possible
by assigning the IO_ flags to the low sixteen bits and the BA_
flags the high sixteen bits. This works because the high sixteen
bits of the IO_ word is reserved for read-ahead and help with
write clustering so will never be used for flags. This merge
lets us get away from code of the form:
if (ioflags & IO_SYNC)
flags |= BA_SYNC;
For the future, I have considered adding a new field to the
vattr structure, va_extsize. This addition could then be
exported through the stat structure to allow applications to
find out the size of the extended attribute storage and also
would provide a more standard interface for truncating them
(via VOP_SETATTR rather than VOP_TRUNCATE).
I am also contemplating adding a pathconf parameter (for
concreteness, lets call it _PC_MAX_EXTSIZE) which would
let an application determine the maximum size of the extended
atribute storage.
Sponsored by: DARPA & NAI Labs.
methodology similar to the vm_map_entry splay and the VM splay that Alan
Cox is working on. Extensive testing has appeared to have shown no
increase in overhead.
Disadvantages
Dirties more cache lines during lookups.
Not as fast as a hash table lookup (but still N log N and optimal
when there is locality of reference).
Advantages
vnode->v_dirtyblkhd is now perfectly sorted, making fsync/sync/filesystem
syncer operate more efficiently.
I get to rip out all the old hacks (some of which were mine) that tried
to keep the v_dirtyblkhd tailq sorted.
The per-vnode splay tree should be easier to lock / SMPng pushdown on
vnodes will be easier.
This commit along with another that Alan is working on for the VM page
global hash table will allow me to implement ranged fsync(), optimize
server-side nfs commit rpcs, and implement partial syncs by the
filesystem syncer (aka filesystem syncer would detect that someone is
trying to get the vnode lock, remembers its place, and skip to the
next vnode).
Note that the buffer cache splay is somewhat more complex then other splays
due to special handling of background bitmap writes (multiple buffers with
the same lblkno in the same vnode), and B_INVAL discontinuities between the
old hash table and the existence of the buffer on the v_cleanblkhd list.
Suggested by: alc
- Cache a pointer to the vnode's object in the buf.
- Hold a reference to that object in addition to the vnode's reference just
to be consistent.
- Cleanup code that got the object indirectly through the vp and VOP calls.
This fixes at least one case where we were calling GETVOBJECT without a lock.
It also avoids an expensive layered call at the cost of another pointer in
struct buf.
improperly clearing more then just the invalid portions of the page. (This
bug is not known to have been triggered by anything).
Submitted by: tegge
MFC after: 7 days
filesystem expands the inode to 256 bytes to make space for 64-bit
block pointers. It also adds a file-creation time field, an ability
to use jumbo blocks per inode to allow extent like pointer density,
and space for extended attributes (up to twice the filesystem block
size worth of attributes, e.g., on a 16K filesystem, there is space
for 32K of attributes). UFS2 fully supports and runs existing UFS1
filesystems. New filesystems built using newfs can be built in either
UFS1 or UFS2 format using the -O option. In this commit UFS1 is
the default format, so if you want to build UFS2 format filesystems,
you must specify -O 2. This default will be changed to UFS2 when
UFS2 proves itself to be stable. In this commit the boot code for
reading UFS2 filesystems is not compiled (see /sys/boot/common/ufsread.c)
as there is insufficient space in the boot block. Once the size of the
boot block is increased, this code can be defined.
Things to note: the definition of SBSIZE has changed to SBLOCKSIZE.
The header file <ufs/ufs/dinode.h> must be included before
<ufs/ffs/fs.h> so as to get the definitions of ufs2_daddr_t and
ufs_lbn_t.
Still TODO:
Verify that the first level bootstraps work for all the architectures.
Convert the utility ffsinfo to understand UFS2 and test growfs.
Add support for the extended attribute storage. Update soft updates
to ensure integrity of extended attribute storage. Switch the
current extended attribute interfaces to use the extended attribute
storage. Add the extent like functionality (framework is there,
but is currently never used).
Sponsored by: DARPA & NAI Labs.
Reviewed by: Poul-Henning Kamp <phk@freebsd.org>
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
without removing the buffer from the vnode's dirty buffer list, which
can result in a panic in NFS. Replaced the code with a call to bundirty()
which deals with it properly.
PR: kern/36108, kern/36174
Submitted by: various people
Special mention: to Danny Schales <dan@coes.LaTech.edu> for providing a core dump that helped me track this down.
MFC after: 1 day
pmap_qremove. pmap_kenter is not safe to use in MI code because it is not
guaranteed to flush the mapping from the tlb on all cpus. If the process
in question is preempted and migrates cpus between the call to pmap_kenter
and pmap_kremove, the original cpu will be left with stale mappings in its
tlb. This is currently not a problem for i386 because we do not use PG_G on
SMP, and thus all mappings are flushed from the tlb on context switches, not
just user mappings. This is not the case on all architectures, and if PG_G
is to be used with SMP on i386 it will be a problem. This was committed by
peter earlier as part of his fine grained tlb shootdown work for i386, which
was backed out for other reasons.
Reviewed by: peter
the bio and buffer structures to have daddr64_t bio_pblkno,
b_blkno, and b_lblkno fields which allows access to disks
larger than a Terabyte in size. This change also requires
that the VOP_BMAP vnode operation accept and return daddr64_t
blocks. This delta should not affect system operation in
any way. It merely sets up the necessary interfaces to allow
the development of disk drivers that work with these larger
disk block addresses. It also allows for the development of
UFS2 which will use 64-bit block addresses.
kern/kern_descrip.c:
Aquire Giant in fdrop_locked when file refcount hits zero, this removes
the requirement for the caller to own Giant for the most part.
kern/kern_ktrace.c:
Aquire Giant in ktrgenio, simplifies locking in upper read/write syscalls.
kern/vfs_bio.c:
Aquire Giant in bwillwrite if needed.
kern/sys_generic.c
Giant pushdown, remove Giant for:
read, pread, write and pwrite.
readv and writev aren't done yet because of the possible malloc calls
for iov to uio processing.
kern/sys_socket.c
Grab giant in the socket fo_read/write functions.
kern/vfs_vnops.c
Grab giant in the vnode fo_read/write functions.
Includes some minor whitespace changes, and re-ordering to be able to document
properly (e.g, grouping of variables and the SYSCTL macro calls for them, where
the documentation has been added.)
Reviewed by: phk (but all errors are mine)
There is some unresolved badness that has been eluding me, particularly
affecting uniprocessor kernels. Turning off PG_G helped (which is a bad
sign) but didn't solve it entirely. Userland programs still crashed.
shootdowns in a couple of key places. Do the same for i386. This also
hides some physical addresses from higher levels and has it use the
generic vm_page_t's instead. This will help for PAE down the road.
Obtained from: jake (MI code, suggestions for MD part)
Remove bowrite(), it is now unused.
This is the first step in getting entirely rid of BIO_ORDERED which is
a generally accepted evil thing.
Approved by: mckusick
commit by Kirk also fixed a softupdates bug that could easily be triggered
by server side NFS.
* An edge case with shared R+W mmap()'s and truncate whereby
the system would inappropriately clear the dirty bits on
still-dirty data. (applicable to all filesystems)
THIS FIX TEMPORARILY DISABLED PENDING FURTHER TESTING.
see vm/vm_page.c line 1641
* The straddle case for VM pages and buffer cache buffers when
truncating. (applicable to NFS client side)
* Possible SMP database corruption due to vm_pager_unmap_page()
not clearing the TLB for the other cpu's. (applicable to NFS
client side but could effect all filesystems). Note: not
considered serious since the corruption occurs beyond the file
EOF.
* When flusing a dirty buffer due to B_CACHE getting cleared,
we were accidently setting B_CACHE again (that is, bwrite() sets
B_CACHE), when we really want it to stay clear after the write
is complete. This resulted in a corrupt buffer. (applicable
to all filesystems but probably only triggered by NFS)
* We have to call vtruncbuf() when ftruncate()ing to remove
any buffer cache buffers. This is still tentitive, I may
be able to remove it due to the second bug fix. (applicable
to NFS client side)
* vnode_pager_setsize() race against nfs_vinvalbuf()... we have
to set n_size before calling nfs_vinvalbuf or the NFS code
may recursively vnode_pager_setsize() to the original value
before the truncate. This is what was causing the user mmap
bus faults in the nfs tester program. (applicable to NFS
client side)
* Fix to softupdates (see ufs/ffs/ffs_inode.c 1.73, commit made
by Kirk).
Testing program written by: Avadis Tevanian, Jr.
Testing program supplied by: jkh / Apple (see Dec2001 posting to freebsd-hackers with Subject 'NFS: How to make FreeBS fall on its face in one easy step')
MFC after: 1 week
in wdrain during a write. This flag needs to be used in devices whos
strategy routines turn-around and issue another high level I/O, such as
when MD turns around and issues a VOP_WRITE to vnode backing store, in order
to avoid deadlocking the dirty buffer draining code.
Remove a vprintf() warning from MD when the backing vnode is found to be
in-use. The syncer of buf_daemon could be flushing the backing vnode at
the time of an MD operation so the warning is not correct.
MFC after: 1 week
- crhold() returns a reference to the ucred whose refcount it bumps.
- crcopy() now simply copies the credentials from one credential to
another and has no return value.
- a new crshared() primitive is added which returns true if a ucred's
refcount is > 1 and false (0) otherwise.
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
timeout callwheel and buffer cache, out of the platform specific areas
and into the machine independant area. i386 and alpha adjusted here.
Other cpus can be fixed piecemeal.
Reviewed by: freebsd-smp, jake
VM caching of disks through mmap() and stopping syncing of open files
that had their last reference in the fs removed (ie: their unsync'ed
pages get discarded on close already, so I made it stop syncing too).
(this commit is just the first stage). Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.
Tor created a while ago, removes the raw I/O piece (that has cache coherency
problems), and adds a buffer cache / VM freeing piece.
Essentially this patch causes O_DIRECT I/O to not be left in the cache, but
does not prevent it from going through the cache, hence the 80%. For
the last 20% we need a method by which the I/O can be issued directly to
buffer supplied by the user process and bypass the buffer cache entirely,
but still maintain cache coherency.
I also have the code working under -stable but the changes made to sys/file.h
may not be MFCable, so an MFC is not on the table yet.
Submitted by: tegge, dillon
- Always call vfs_setdirty() with vm_mtx held.
- Fix an old comment: vm_hold_unload_pages is called vm_hold_free_pages()
nowadays.
- Always call vm_hold_free_pages() w/o vm_mtx held.
vm_mtx does not recurse and is required for most low level
vm operations.
faults can not be taken without holding Giant.
Memory subsystems can now call the base page allocators safely.
Almost all atomic ops were removed as they are covered under the
vm mutex.
Alpha and ia64 now need to catch up to i386's trap handlers.
FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).
Reviewed (partially) by: jake, jhb
VOP_BWRITE() was a hack which made it possible for NFS client
side to use struct buf with non-bio backing.
This patch takes a more general approach and adds a bp->b_op
vector where more methods can be added.
The success of this patch depends on bp->b_op being initialized
all relevant places for some value of "relevant" which is not
easy to determine. For now the buffers have grown a b_magic
element which will make such issues a tiny bit easier to debug.
sized blocks. To enable this option, use: `sysctl -w debug.bigcgs=1'.
Add debugging option to disable background writes of cylinder
groups. To enable this option, use: `sysctl -w debug.dobkgrdwrite=0'.
These debugging options should be tried on systems that are panicing
with corrupted cylinder group maps to see if it makes the problem
go away. The set of panics in question are:
ffs_clusteralloc: map mismatch
ffs_nodealloccg: map corrupted
ffs_nodealloccg: block not in map
ffs_alloccg: map corrupted
ffs_alloccg: block not in map
ffs_alloccgblk: cyl groups corrupted
ffs_alloccgblk: can't find blk in cyl
ffs_checkblk: partially free fragment
The following panics are less likely to be related to this problem,
but might be helped by these debugging options:
ffs_valloc: dup alloc
ffs_blkfree: freeing free block
ffs_blkfree: freeing free frag
ffs_vfree: freeing free inode
If you try these options, please report whether they helped reduce your
bitmap corruption panics to Kirk McKusick at <mckusick@mckusick.com>
and to Matt Dillon <dillon@earth.backplane.com>.
hit on the client side and prevent the server side from retiring writes.
Pipeline operations turned off for all READs (no big loss since reads are
usually synchronous) and for NFS writes, and left on for the default bwrite().
(MFC expected prior to 4.3 freeze)
Testing by: mjacob, dillon
mtx_enter(lock, type) becomes:
mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)
similarily, for releasing a lock, we now have:
mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.
The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.
Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:
MTX_QUIET and MTX_NOSWITCH
The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:
mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.
Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.
Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.
Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.
Finally, caught up to the interface changes in all sys code.
Contributors: jake, jhb, jasone (in no particular order)
by myself. It solves a serious vm_map corruption problem that can occur
with the buffer cache when block sizes > 64K are used. This code has been
heavily tested in -stable but only tested somewhat on -current. An MFC
will occur in a few days. My additions include the vm_map_simplify_entry()
and minor buffer cache boundry case fix.
Make the buffer cache use a system map for buffer cache KVM rather then a
normal map.
Ensure that VM objects are not allocated for system maps. There were cases
where a buffer map could wind up with a backing VM object -- normally
harmless, but this could also result in the buffer cache blocking in places
where it assumes no blocking will occur, possibly resulting in corrupted
maps.
Fix a minor boundry case in the buffer cache size limit is reached that
could result in non-optimal code.
Add vm_map_simplify_entry() calls to prevent 'creeping proliferation'
of vm_map_entry's in the buffer cache's vm_map. Previously only a simple
linear optimization was made. (The buffer vm_map typically has only a
handful of vm_map_entry's. This stabilizes it at that level permanently).
PR: 20609
Submitted by: (Tor Egge) tegge
in 4.2-REL which I ripped out in -stable and -current when implementing the
low-memory handling solution. However, maxlaunder turns out to be the saving
grace in certain very heavily loaded systems (e.g. newsreader box). The new
algorithm limits the number of pages laundered in the first pageout daemon
pass. If that is not sufficient then suceessive will be run without any
limit.
Write I/O is now pipelined using two sysctls, vfs.lorunningspace and
vfs.hirunningspace. This prevents excessive buffered writes in the
disk queues which cause long (multi-second) delays for reads. It leads
to more stable (less jerky) and generally faster I/O streaming to disk
by allowing required read ops (e.g. for indirect blocks and such) to occur
without interrupting the write stream, amoung other things.
NOTE: eventually, filesystem write I/O pipelining needs to be done on a
per-device basis. At the moment it is globalized.
Removed most of the hacks that were trying to deal with low-memory
situations prior to now.
The new code is based on the concept that I/O must be able to function in
a low memory situation. All major modules related to I/O (except
networking) have been adjusted to allow allocation out of the system
reserve memory pool. These modules now detect a low memory situation but
rather then block they instead continue to operate, then return resources
to the memory pool instead of cache them or leave them wired.
Code has been added to stall in a low-memory situation prior to a vnode
being locked.
Thus situations where a process blocks in a low-memory condition while
holding a locked vnode have been reduced to near nothing. Not only will
I/O continue to operate, but many prior deadlock conditions simply no
longer exist.
Implement a number of VFS/BIO fixes
(found by Ian): in biodone(), bogus-page replacement code, the loop
was not properly incrementing loop variables prior to a continue
statement. We do not believe this code can be hit anyway but we
aren't taking any chances. We'll turn the whole section into a
panic (as it already is in brelse()) after the release is rolled.
In biodone(), the foff calculation was incorrectly
clamped to the iosize, causing the wrong foff to be calculated
for pages in the case of an I/O error or biodone() called without
initiating I/O. The problem always caused a panic before. Now it
doesn't. The problem is mainly an issue with NFS.
Fixed casts for ~PAGE_MASK. This code worked properly before only
because the calculations use signed arithmatic. Better to properly
extend PAGE_MASK first before inverting it for the 64 bit masking
op.
In brelse(), the bogus_page fixup code was improperly throwing
away the original contents of 'm' when it did the j-loop to
fix the bogus pages. The result was that it would potentially
invalidate parts of the *WRONG* page(!), leading to corruption.
There may still be cases where a background bitmap write is
being duplicated, causing potential corruption. We have identified
a potentially serious bug related to this but the fix is still TBD.
So instead this patch contains a KASSERT to detect the problem
and panic the machine rather then continue to corrupt the filesystem.
The problem does not occur very often.. it is very hard to
reproduce, and it may or may not be the cause of the corruption
people have reported.
Review by: (VFS/BIO: mckusick, Ian Dowse <iedowse@maths.tcd.ie>)
Testing by: (VM/Deadlock) Paul Saab <ps@yahoo-inc.com>
Add lockdestroy() and appropriate invocations, which corresponds to
lockinit() and must be called to clean up after a lockmgr lock is no
longer needed.
include:
* Mutual exclusion is used instead of spl*(). See mutex(9). (Note: The
alpha port is still in transition and currently uses both.)
* Per-CPU idle processes.
* Interrupts are run in their own separate kernel threads and can be
preempted (i386 only).
Partially contributed by: BSDi (BSD/OS)
Submissions by (at least): cp, dfr, dillon, grog, jake, jhb, sheldonh
the gating of system calls that cause modifications to the underlying
filesystem. The gating can be enabled by any filesystem that needs
to consistently suspend operations by adding the vop_stdgetwritemount
to their set of vnops. Once gating is enabled, the function
vfs_write_suspend stops all new write operations to a filesystem,
allows any filesystem modifying system calls already in progress
to complete, then sync's the filesystem to disk and returns. The
function vfs_write_resume allows the suspended write operations to
begin again. Gating is not added by default for all filesystems as
for SMP systems it adds two extra locks to such critical kernel
paths as the write system call. Thus, gating should only be added
as needed.
Details on the use and current status of snapshots in FFS can be
found in /sys/ufs/ffs/README.snapshot so for brevity and timelyness
is not included here. Unless and until you create a snapshot file,
these changes should have no effect on your system (famous last words).
<sys/bio.h>.
<sys/bio.h> is now a prerequisite for <sys/buf.h> but it shall
not be made a nested include according to bdes teachings on the
subject of nested includes.
Diskdrivers and similar stuff below specfs::strategy() should no
longer need to include <sys/buf.> unless they need caching of data.
Still a few bogus uses of struct buf to track down.
Repocopy by: peter
Exceptions:
Vinum untouched. This means that it cannot be compiled.
Greg Lehey is on the case.
CCD not converted yet, casts to struct buf (still safe)
atapi-cd casts to struct buf to examine B_PHYS
(Much of this done by script)
Move B_ORDERED flag to b_ioflags and call it BIO_ORDERED.
Move b_pblkno and b_iodone_chain to struct bio while we transition, they
will be obsoleted once bio structs chain/stack.
Add bio_queue field for struct bio aware disksort.
Address a lot of stylistic issues brought up by bde.
fragmentation problem due to geteblk() reserving too much space for the
buffer and imposes a larger granularity (16K) on KVA reservations for
the buffer cache to avoid fragmentation issues. The buffer cache size
calculations have been redone to simplify them (fewer defines, better
comments, less chance of running out of KVA).
The geteblk() fix solves a performance problem that DG was able reproduce.
This patch does not completely fix the KVA fragmentation problems, but
it goes a long way
Mostly Reviewed by: bde and others
Approved by: jkh
substitute BUF_WRITE(foo) for VOP_BWRITE(foo->b_vp, foo)
substitute BUF_STRATEGY(foo) for VOP_STRATEGY(foo->b_vp, foo)
This patch is machine generated except for the ccd.c and buf.h parts.
field in struct buf: b_iocmd. The b_iocmd is enforced to have
exactly one bit set.
B_WRITE was bogusly defined as zero giving rise to obvious coding
mistakes.
Also eliminate the redundant struct buf flag B_CALL, it can just
as efficiently be done by comparing b_iodone to NULL.
Should you get a panic or drop into the debugger, complaining about
"b_iocmd", don't continue. It is likely to write on your disk
where it should have been reading.
This change is a step in the direction towards a stackable BIO capability.
A lot of this patch were machine generated (Thanks to style(9) compliance!)
Vinum users: Greg has not had time to test this yet, be careful.
again (without this the rollback analysis was being lost). Should reduce
the write count for most workloads.
Submitted by: Craig A Soules <soules+@andrew.cmu.edu>
1) Fastpath deletions. When a file is being deleted, check to see if it
was so recently created that its inode has not yet been written to
disk. If so, the delete can proceed to immediately free the inode.
2) Background writes: No file or block allocations can be done while the
bitmap is being written to disk. To avoid these stalls, the bitmap is
copied to another buffer which is written thus leaving the original
available for futher allocations.
3) Link count tracking. Constantly track the difference in i_effnlink and
i_nlink so that inodes that have had no change other than i_effnlink
need not be written.
4) Identify buffers with rollback dependencies so that the buffer flushing
daemon can choose to skip over them.
stressful situations. buf_daemon now makes a distinction between
being woken up and its sleep timing out, and as a consequence is now
much better able to dynamically tune itself to its environment.
Reviewed by: Alfred Perlstein <bright@wintelcom.net>
drops the counting in bwrite and puts it all in spec_strategy.
I did some tests and verified that the counts collected for writes
in spec_strategy is identical to the counts that we previously
collected in bwrite. We now also get read counts (async reads
come from requests for read-ahead blocks). Note that you need
to compile a new version of mount to get the read counts printed
out. The old mount binary is completely compatible, the only
reason to install a new mount is to get the read counts printed.
Submitted by: Craig A Soules <soules+@andrew.cmu.edu>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
Alot of the code in sys/kern directly accesses the *Q_HEAD and *Q_ENTRY
structures for list operations. This patch makes all list operations
in sys/kern use the queue(3) macros, rather than directly accessing the
*Q_{HEAD,ENTRY} structures.
This batch of changes compile to the same object files.
Reviewed by: phk
Submitted by: Jake Burkholder <jake@checker.org>
PR: 14914
Merge the contents (less some trivial bordering the silly comments)
of <vm/vm_prot.h> and <vm/vm_inherit.h> into <vm/vm.h>. This puts
the #defines for the vm_inherit_t and vm_prot_t types next to their
typedefs.
This paves the road for the commit to follow shortly: change
useracc() to use VM_PROT_{READ|WRITE} rather than B_{READ|WRITE}
as argument.
slightly older version of this code was tested by BDE and I.
Also fixes a lockup situation when kva gets too fragmented.
Remove the maxvmiobufspace variable and sysctl, they are no longer
used. Also cleanup (remove) #if 0 sections from prior commits.
This code is more of a hack, but presumably the whole buffer cache
implementation is going to be rewritten in the next year so it's no
big deal.
improperly ignored the B_INVAL flag when acting on the B_ERROR.
If both B_INVAL and B_ERROR are set the buffer is typically out of the
underlying device's block range and must be destroyed. If only B_ERROR
is set (for a write), a write error occured and operation remains as it
was before: the buffer must be redirtied to avoid corrupting the
filesystem state.
Reviewed by: David Greenman <dg@root.com>
Submitted by: Tor.Egge@fast.no
large (1G) memory machine configurations. I was able to run 'dbench 32'
on a 32MB system without bring the machine to a grinding halt.
* buffer cache hash table now dynamically allocated. This will
have no effect on memory consumption for smaller systems and
will help scale the buffer cache for larger systems.
* minor enhancement to pmap_clearbit(). I noticed that
all the calls to it used constant arguments. Making
it an inline allows the constants to propogate to
deeper inlines and should produce better code.
* removal of inherent vfs_ioopt support through the emplacement
of appropriate #ifdef's, with John's permission. If we do not
find a use for it by the end of the year we will remove it entirely.
* removal of getnewbufloops* counters & sysctl's - no longer
necessary for debugging, getnewbuf() is now optimal.
* buffer hash table functions removed from sys/buf.h and localized
to vfs_bio.c
* VFS_BIO_NEED_DIRTYFLUSH flag and support code added
( bwillwrite() ), allowing processes to block when too many dirty
buffers are present in the system.
* removal of a softdep test in bdwrite() that is no longer necessary
now that bdwrite() no longer attempts to flush dirty buffers.
* slight optimization added to bqrelse() - there is no reason
to test for available buffer space on B_DELWRI buffers.
* addition of reverse-scanning code to vfs_bio_awrite().
vfs_bio_awrite() will attempt to locate clusterable areas
in both the forward and reverse direction relative to the
offset of the buffer passed to it. This will probably not
make much of a difference now, but I believe we will start
to rely on it heavily in the future if we decide to shift
some of the burden of the clustering closer to the actual
I/O initiation.
* Removal of the newbufcnt and lastnewbuf counters that Kirk
added. They do not fix any race conditions that haven't already
been fixed by the gbincore() test done after the only call
to getnewbuf(). getnewbuf() is a static, so there is no chance
of it being misused by other modules. ( Unless Kirk can think
of a specific thing that this code fixes. I went through it
very carefully and didn't see anything ).
* removal of VOP_ISLOCKED() check in flushbufqueues(). I do not
think this check is necessary, the buffer should flush properly
whether the vnode is locked or not. ( yes? ).
* removal of extra arguments passed to getnewbuf() that are not
necessary.
* missed cluster_wbuild() that had to be a cluster_wbuild_wb() in
vfs_cluster.c
* vn_write() now calls bwillwrite() *PRIOR* to locking the vnode,
which should greatly aid flushing operations in heavy load
situations - both the pageout and update daemons will be able
to operate more efficiently.
* removal of b_usecount. We may add it back in later but for now
it is useless. Prior implementations of the buffer cache never
had enough buffers for it to be useful, and current implementations
which make more buffers available might not benefit relative to
the amount of sophistication required to implement a b_usecount.
Straight LRU should work just as well, especially when most things
are VMIO backed. I expect that (even though John will not like
this assumption) directories will become VMIO backed some point soon.
Submitted by: Matthew Dillon <dillon@backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
QUEUE_AGE, QUEUE_LRU, and QUEUE_EMPTY we instead have QUEUE_CLEAN,
QUEUE_DIRTY, QUEUE_EMPTY, and QUEUE_EMPTYKVA. With this patch clean
and dirty buffers have been separated. Empty buffers with KVM
assignments have been separated from truely empty buffers. getnewbuf()
has been rewritten and now operates in a 100% optimal fashion. That is,
it is able to find precisely the right kind of buffer it needs to
allocate a new buffer, defragment KVM, or to free-up an existing buffer
when the buffer cache is full (which is a steady-state situation for
the buffer cache).
Buffer flushing has been reorganized. Previously buffers were flushed
in the context of whatever process hit the conditions forcing buffer
flushing to occur. This resulted in processes blocking on conditions
unrelated to what they were doing. This also resulted in inappropriate
VFS stacking chains due to multiple processes getting stuck trying to
flush dirty buffers or due to a single process getting into a situation
where it might attempt to flush buffers recursively - a situation that
was only partially fixed in prior commits. We have added a new daemon
called the buf_daemon which is responsible for flushing dirty buffers
when the number of dirty buffers exceeds the vfs.hidirtybuffers limit.
This daemon attempts to dynamically adjust the rate at which dirty buffers
are flushed such that getnewbuf() calls (almost) never block.
The number of nbufs and amount of buffer space is now scaled past the
8MB limit that was previously imposed for systems with over 64MB of
memory, and the vfs.{lo,hi}dirtybuffers limits have been relaxed
somewhat. The number of physical buffers has been increased with the
intention that we will manage physical I/O differently in the future.
reassignbuf previously attempted to keep the dirtyblkhd list sorted which
could result in non-deterministic operation under certain conditions,
such as when a large number of dirty buffers are being managed. This
algorithm has been changed. reassignbuf now keeps buffers locally sorted
if it can do so cheaply, and otherwise gives up and adds buffers to
the head of the dirtyblkhd list. The new algorithm is deterministic but
not perfect. The new algorithm greatly reduces problems that previously
occured when write_behind was turned off in the system.
The P_FLSINPROG proc->p_flag bit has been replaced by the more descriptive
P_BUFEXHAUST bit. This bit allows processes working with filesystem
buffers to use available emergency reserves. Normal processes do not set
this bit and are not allowed to dig into emergency reserves. The purpose
of this bit is to avoid low-memory deadlocks.
A small race condition was fixed in getpbuf() in vm/vm_pager.c.
Submitted by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
(really this time) fix pageout to swap and a couple of clustering cases.
This simplifies BUF_KERNPROC() so that it unconditionally reassigns the
lock owner rather than testing B_ASYNC and having the caller decide when
to do the reassign. At present this is required because some places use
B_CALL/b_iodone to free the buffers without B_ASYNC being set. Also,
vfs_cluster.c explicitly calls BUF_KERNPROC() when attaching the buffers
rather than the parent walking the cluster_head tailq.
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
lockmgr locks. This commit should be functionally equivalent to the old
semantics. That is, all buffer locking is done with LK_EXCLUSIVE
requests. Changes to take advantage of LK_SHARED and LK_RECURSIVE will
be done in future commits.
