Filesystems which want to use it in limited capacity can employ the
VOP_UNLOCK_FLAGS macro.
Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D21427
Don't hold the scheduler lock while doing context switches. Instead we
unlock after selecting the new thread and switch within a spinlock
section leaving interrupts and preemption disabled to prevent local
concurrency. This means that mi_switch() is entered with the thread
locked but returns without. This dramatically simplifies scheduler
locking because we will not hold the schedlock while spinning on
blocked lock in switch.
This change has not been made to 4BSD but in principle it would be
more straightforward.
Discussed with: markj
Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22778
via sys_sync(2). Minor cleanup, no functional changes.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19366
the vnode, logical block number, and size of data block that is
being requested. They then use the VOP_BMAP function to calculate
the mapping from logical block number to physical block number from
which to access the data. This change expands the interface to also
pass the physical block number in cases where the VOP_MAP function
may no longer work, for example when a file is being truncated.
No functional change.
Reviewed by: kib
Tested by: Peter Holm
Sponsored by: Netflix
Recent changes to busy/valid/dirty have enabled page based synchronization
and the object lock is no longer required in many cases.
Reviewed by: kib
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21597
Atomics are used for page busy and valid state when the shared busy is
held. The details of the locking protocol and valid and dirty
synchronization are in the updated vm_page.h comments.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21594
This is the first in a series of patches that promotes the page busy field
to a first class lock that no longer requires the object lock for
consistency.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21548
Refcount waiting will set some flag bits in the refcount value.
Make sure these bits get cleared by using the REFCOUNT_COUNT()
macro to obtain the actual refcount.
Differential Revision: https://reviews.freebsd.org/D21620
Reviewed by: kib@, markj@
MFC after: 1 week
Sponsored by: Mellanox Technologies
Setting the B_INVALONERR flag before a synchronous write causes the buf
cache to forcibly invalidate contents if the write fails (BIO_ERROR).
This is intended to be used to allow layers above the buffer cache to make
more informed decisions about when discarding dirty buffers without
successful write is acceptable.
As a proof of concept, use in msdosfs to handle failures to mark the on-disk
'dirty' bit during rw mount or ro->rw update.
Extending this to other filesystems is left as future work.
PR: 210316
Reviewed by: kib (with objections)
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D21539
races with page busy state. The object lock is still used as an interlock
to ensure that the identity stays valid. Most callers should use
vm_page_sleep_if_busy() to handle the locking particulars.
Reviewed by: alc, kib, markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21255
These were fully neutered in r177676 (2008), but not removed at the time for
unclear reasons. They're totally dead code, so go ahead and yank them now.
No functional change.
Both of these functions atomically unwire a page, optionally attempt
to free the page, and enqueue or requeue the page. Add functions
vm_page_release() and vm_page_release_locked() to perform the same task.
The latter must be called with the page's object lock held.
As a side effect of this refactoring, the buffer cache will no longer
attempt to free mapped pages when completing direct I/O. This is
consistent with the handling of pages by sendfile(SF_NOCACHE).
Reviewed by: alc, kib
MFC after: 2 weeks
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D20986
Similar to r348026, exhaustive search for uses of CTRn() and cross reference
ktr.h includes. Where it was obvious that an OS compat header of some kind
included ktr.h indirectly, .c files were left alone. Some of these files
clearly got ktr.h via header pollution in some scenarios, or tinderbox would
not be passing prior to this revision, but go ahead and explicitly include it
in files using it anyway.
Like r348026, these CUs did not show up in tinderbox as missing the include.
Reported by: peterj (arm64/mp_machdep.c)
X-MFC-With: r347984
Sponsored by: Dell EMC Isilon
These predicates are vestigal and cannot be true today. For example,
idle threads are not allowed to acquire locks.
Also cache curthread in breada().
No functional change intended.
Reviewed by: kib, mckusick
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20066
extended attributes, the kernel can panic with either "ffs_truncate3"
or with "softdep_deallocate_dependencies: dangling deps".
The problem arises because the flushbuflist() function which is
called to clear out buffers is passed either the V_NORMAL flag to
indicate that it should flush buffer associated with the contents
of the file or the V_ALT flag to indicate that it should flush the
buffers associated with the extended attribute data. The buffers
containing the extended attribute data are identified by having
their BX_ALTDATA flag set in the buffer's b_xflags field. The
BX_ALTDATA flag is set on the buffer when the extended attribute
block is first allocated or when its contents are read in from the
disk.
On a busy system, a buffer may be reused for another purpose, but
the contents of the block that it contained continues to be held
in the main page cache. Each physical page is identified as holding
the contents of a logical block within a specified file (identified
by a vnode). When a request is made to read a file, the kernel first
looks for the block in the existing buffers. If it is not found
there, it checks the page cache to see if it is still there. If
it is found in the page cache, then it is remapped into a new
buffer thus avoiding the need to read it in from the disk.
The bug is that when a buffer request made for an extended attribute
is fulfilled by reconstituting a buffer from the page cache rather
than reading it in from disk, the BX_ALTDATA flag was not being
set. Thus the flushbuflist() function would never clear it out and
the "ffs_truncate3" panic would occur because the vnode being cleared
still had buffers on its clean-buffer list. If the extended attribute
was being updated, it is first read, then updated, and finally
written. If the read is fulfilled by reconstituting the buffer
from the page cache the BX_ALTDATA flag was not set and thus the
dirty buffer would never be flushed by flushbuflist(). Eventually
the buffer would be recycled. Since it was never written it would
have an unfinished dependency which would trigger the
"softdep_deallocate_dependencies: dangling deps" panic.
The fix is to ensure that the BX_ALTDATA flag is set when a buffer
has been reconstituted from the page cache.
PR: 230962
Reported by: 2t8mr7kx9f@protonmail.com
Reviewed by: kib
Tested by: Peter Holm
MFC after: 1 week
Sponsored by: Netflix
vnode pointer (b_vp). The value of b_vp can be used by "show vnode"
to print the vnode and "show vnodebufs" to print all the clean and
dirty buffers associated with the vnode (which should include this
buffer).
Sponsored by: Netflix
o In vm_pager_bufferinit() create pbuf_zone and start accounting on how many
pbufs are we going to have set.
In various subsystems that are going to utilize pbufs create private zones
via call to pbuf_zsecond_create(). The latter calls uma_zsecond_create(),
and sets a limit on created zone. After startup preallocate pbufs according
to requirements of all pbuf zones.
Subsystems that used to have a private limit with old allocator now have
private pbuf zones: md(4), fusefs, NFS client, smbfs, VFS cluster, FFS,
swap, vnode pager.
The following subsystems use shared pbuf zone: cam(4), nvme(4), physio(9),
aio(4). They should have their private limits, but changing that is out of
scope of this commit.
o Fetch tunable value of kern.nswbuf from init_param2() and while here move
NSWBUF_MIN to opt_param.h and eliminate opt_swap.h, that was holding only
this option.
Default values aren't touched by this commit, but they probably should be
reviewed wrt to modern hardware.
This change removes a tight bottleneck from sendfile(2) operation, that
uses pbufs in vnode pager. Other pagers also would benefit from faster
allocation.
Together with: gallatin
Tested by: pho
Filesystem or pager completion callbacks are generally non-functional
after a panic and may trigger deadlocks if invoked in this context
(e.g., by attempting to destroying a buffer mapping). To avoid this
situation, short-circuit I/O completion in biodone().
Reviewed by: imp
Discussed with: mav
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D15592
- Create getblkx(9) variant of getblk(9) which can return error.
- Add GB_NOSPARSE flag for getblk()/getblkx() which requests that BMAP
was performed before the buffer is created, and EJUSTRETURN returned
in case the requested block does not exist.
- Make ffs_read() use GB_NOSPARSE to avoid instantiating buffer (and
allocating the pages for it), copying from zero_region instead.
The end result is less page allocations and buffer recycling when a
hole is read, which is important for some benchmarks.
Requested and reviewed by: jeff
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D14917
With r332974, when performing a synchronized access of a page's "queue"
field, one must first check whether the page is logically dequeued. If
so, then the page lock does not prevent the page from being removed
from its page queue. Intoduce vm_page_queue(), which returns the page's
logical queue index. In some cases, direct access to the "queue" field
is still required, but such accesses should be confined to sys/vm.
Reported and tested by: pho
Reviewed by: kib
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D15280
kproc_suspend_check. In r329612 bufspacedaemon was turned into a thread
of the bufdaemon process causing both to call kproc_suspend_check with the
same proc argument and that function contains the following while loop:
while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
wakeup(&p->p_siglist);
msleep(&p->p_siglist, &p->p_mtx, PPAUSE, "kpsusp", 0);
}
So one thread wakes up the other and the other wakes up the first again,
locking up UP machines on shutdown.
Also register the shutdown handlers with SHUTDOWN_PRI_LAST + 100 so they
run after the syncer has shutdown, because the syncer can cause a
situation where bufdaemon help is needed to proceed.
PR: 227404
Reviewed by: kib
Tested by: cy, rmacklem
opt_compat.h is mentioned in nearly 180 files. In-progress network
driver compabibility improvements may add over 100 more so this is
closer to "just about everywhere" than "only some files" per the
guidance in sys/conf/options.
Keep COMPAT_LINUX32 in opt_compat.h as it is confined to a subset of
sys/compat/linux/*.c. A fake _COMPAT_LINUX option ensure opt_compat.h
is created on all architectures.
Move COMPAT_LINUXKPI to opt_dontuse.h as it is only used to control the
set of compiled files.
Reviewed by: kib, cem, jhb, jtl
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14941
The object lock was only needed when attempting to free B_DIRECT
buffer pages, and for testing for invalid pages (and freeing them
if so). Handle the latter by instead moving invalid pages near the head
of the inactive queue, where they will be reclaimed quickly.
Reviewed by: alc, kib, jeff
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D14778
arg2 is an intmax_t, which on 32-bit architectures is 64 bits, wider than a
pointer. When &bdomain[i] is added to arg2 it widens from uintptr_t to
intmax_t, then gcc whines when it gets cast to a pointer. Casting through
uintptr_t silences this warning.
In many cases the page is not enqueued so the change will have no
effect. However, the change is needed to support an optimization in
the fault handler and in some cases (sendfile, the buffer cache) it
was being emulated by the caller anyway.
Reviewed by: alc
Tested by: pho
MFC after: 2 weeks
X-Differential Revision: https://reviews.freebsd.org/D14625
where we had not hit global dirty limits but a single queue was starved
for space by dirty buffers. A single buf_daemon is maintained for now.
Add a bd_speedup() when we are low on bufspace. This can happen due to SUJ
keeping many bufs locked until a cg block is written. Document this with
a comment.
Fix sysctls to work with per-domain variables. Add more ddb debugging.
Reported by: pho
Reviewed by: kib
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14705
It is believed that the conditions Coverity indicated were actually
impossible to hit. So this patch just adds a cleanup to only compute
v_mount once in brelse(), and in vfs_bio_getpages() always initializes error
to zero to appease the static analyzer.
No functional change intended.
Submitted by: Darrick Lew <darrick.freebsd AT gmail.com>
Reviewed by: kib
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14613
Provide multiple clean queues partitioned into 'domains'. Each domain manages
its own bufspace and has its own bufspace daemon. Each domain has a set of
subqueues indexed by the current cpuid to reduce lock contention on the cleanq.
Refine the sleep/wakeup around the bufspace daemon to use atomics as much as
possible.
Add a B_REUSE flag that is used to requeue bufs during the scan to approximate
LRU rather than locking the queue on every use of a frequently accessed buf.
Implement bufspace_reserve with only atomic_fetchadd to avoid loop restarts.
Reviewed by: markj
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14274
significant source of cache line contention from vm_page_alloc(). Use
accessors and vm_page_unwire_noq() so that the mechanism can be easily
changed in the future.
Reviewed by: markj
Discussed with: kib, glebius
Tested by: pho (earlier version)
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14273
to make the order of operations clearer to avoid the race condition
that was fixed in r328914. In particular, this commit corrects a
similar race that existed in the soft updates callback.
Doing some sleuthing through the SVN repository, it appears that
bufdone_finish() was added to support XFS:
------------------------------------------------------------------------
r153192 | rodrigc | 2005-12-06 19:39:08 -0800 (Tue, 06 Dec 2005) | 13 lines
Changes imported from XFS for FreeBSD project:
- add fields to struct buf (needed by XFS)
- 3 private fields: b_fsprivate1, b_fsprivate2, b_fsprivate3
- b_pin_count, count of pinned buffer
- add new B_MANAGED flag
- add breada() function to initiate asynchronous I/O on read-ahead blocks.
- add bufdone_finish(), bpin(), bunpin_wait() functions
Patches provided by: kan
Reviewed by: phk
Silence on: arch@
------------------------------------------------------------------------
It does not appear to ever have been used for anything else. XFS was
disconnected in r241607:
------------------------------------------------------------------------
r241607 | attilio | 2012-10-16 03:04:00 -0700 (Tue, 16 Oct 2012) | 5 lines
Disconnect non-MPSAFE XFS from the build in preparation for dropping
GIANT from VFS.
This is not targeted for MFC.
------------------------------------------------------------------------
and removed entirely in r247631:
------------------------------------------------------------------------
r247631 | attilio | 2013-03-02 07:33:54 -0800 (Sat, 02 Mar 2013) | 5 lines
Garbage collect XFS bits which are now already completely disconnected
from the tree since few months.
This is not targeted for MFC.
------------------------------------------------------------------------
Since XFS support is gone, there is no reason to retain biodone_finish().
Suggested by: Warner Losh (imp)
Discussed with: cem, kib
Tested by: Peter Holm (pho)
Previously, wiring a page would cause it to be removed from its page
queue. In the common case, unwiring causes it to be enqueued at the tail
of that page queue. This change modifies vm_page_wire() to not dequeue
the page, thus avoiding the highly contended page queue locks. Instead,
vm_page_unwire() takes care of requeuing the page as a single operation,
and the page daemon dequeues wired pages as they are encountered during
a queue scan to avoid needlessly revisiting them later. For pages in
PQ_ACTIVE we do even better, since a requeue is unnecessary.
The change improves scalability for some common workloads. For instance,
threads wiring pages into the buffer cache no longer need to modify
global page queues, and unwiring is usually done by the bufspace thread,
so concurrency is not as much of an issue. As another example, many
sysctl handlers wire the output buffer to avoid faults on copyout, and
since the buffer is likely to be in PQ_ACTIVE, we now entirely avoid
modifying the page queue in this case.
The change also adds a block comment describing some properties of
struct vm_page's reference counters, and the busy lock.
Reviewed by: jeff
Discussed with: alc, kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D11943
systems running with a heavy filesystem load. Tracking down this
bug was elusive because there were actually two problems. Sometimes
the in-memory check hash was wrong and sometimes the check hash
computed when doing the read was wrong. The occurrence of either
error caused a check-hash mismatch to be reported.
The first error was that the check hash in the in-memory cylinder
group was incorrect. This error was caused by the following
sequence of events:
- We read a cylinder-group buffer and the check hash is valid.
- We update its cg_time and cg_old_time which makes the in-memory
check-hash value invalid but we do not mark the cylinder group dirty.
- We do not make any other changes to the cylinder group, so we
never mark it dirty, thus do not write it out, and hence never
update the incorrect check hash for the in-memory buffer.
- Later, the buffer gets freed, but the page with the old incorrect
check hash is still in the VM cache.
- Later, we read the cylinder group again, and the first page with
the old check hash is still in the VM cache, but some other pages
are not, so we have to do a read.
- The read does not actually get the first page from disk, but rather
from the VM cache, resulting in the old check hash in the buffer.
- The value computed after doing the read does not match causing the
error to be printed.
The fix for this problem is to only set cg_time and cg_old_time as
the cylinder group is being written to disk. This keeps the in-memory
check-hash valid unless the cylinder group has had other modifications
which will require it to be written with a new check hash calculated.
It also requires that the check hash be recalculated in the in-memory
cylinder group when it is marked clean after doing a background write.
The second problem was that the check hash computed at the end of the
read was incorrect because the calculation of the check hash on
completion of the read was being done too soon.
- When a read completes we had the following sequence:
- bufdone()
-- b_ckhashcalc (calculates check hash)
-- bufdone_finish()
--- vfs_vmio_iodone() (replaces bogus pages with the cached ones)
- When we are reading a buffer where one or more pages are already
in memory (but not all pages, or we wouldn't be doing the read),
the I/O is done with bogus_page mapped in for the pages that exist
in the VM cache. This mapping is done to avoid corrupting the
cached pages if there is any I/O overrun. The vfs_vmio_iodone()
function is responsible for replacing the bogus_page(s) with the
cached ones. But we were calculating the check hash before the
bogus_page(s) were replaced. Hence, when we were calculating the
check hash, we were partly reading from bogus_page, which means
we calculated a bad check hash (e.g., because multiple pages have
been mapped to bogus_page, so its contents are indeterminate).
The second fix is to move the check-hash calculation from bufdone()
to bufdone_finish() after the call to vfs_vmio_iodone() so that it
computes the check hash over the correct set of pages.
With these two changes, the occasional cylinder-group check-hash
errors are gone.
Submitted by: David Pfitzner <dpfitzner@netflix.com>
Reviewed by: kib
Tested by: David Pfitzner
Previously the calculations were done as if the requested region
ended at the start of the last requested page, not its end.
The problem as actually quite minor as it affected only stats and
page prefaulting, not the actual page data, and only with specific
parameters.
Reviewed by: kib (previous version)
MFC after: 2 weeks
