closing a window where a file system using softupdates could be async
for a short while if both MNT_UPDATE and MNT_ASYNC were passed as flags
to nmount(). Add MNTK_SOFTDEP flag to ensure that softdep_mount()
doesn't increase mnt_noasync multiple times.
switch by worklist type contains two for() loops, for D_INDIRDEP and
D_PAGEDEP. On error, these loops are exited by break, where the switch
actually shall be leaved. Use goto instead of break to reach the error
handling code.
Reported by: Peter Holm
Reviewed by: tegge
Approved by: pjd (mentor)
MFC after: 2 weeks
assuming them to be inflight write buffers. This is not always the case.
bufdaemon might hold the buffer lock and give up writing the buffer due to it
having dependencies, the file system being suspended or the vnode lock being
held by another thread. When bufdaemon decides to write the buffer there is
still a window before bufobj_wref() has been called, allowing other threads to
believe that the vnode has no dirty buffers or inflight writes.
Try harder to flush first block of new subdirectory to get rid of MKDIR_BODY
dependency.
This does not do what I wanted as all dirty buffers must be flushed
by the call to ffs_sync and any remaining dependency work would mean
that this failed.
Pointed out by: tegge
replacement for vn_write_suspend_wait() to better account for secondary write
processing.
Close race where secondary writes could be started after ffs_sync() returned
but before the file system was marked as suspended.
Detect if secondary writes or softdep processing occurred during vnode sync
loop in ffs_sync() and retry the loop if needed.
has many positive effects including improved smp locking, reducing
interdependencies between mounts that can lead to deadlocks, etc.
- Add the softdep worklist and various counters to the ufsmnt structure.
- Add a mount pointer to the workitem and remove mount pointers from the
various structures derived from the workitem as they are now redundant.
- Remove the poor-man's semaphore protecting softdep_process_worklist and
softdep_flushworklist. Several threads may now process the list
simultaneously.
- Add softdep_waitidle() to block the thread until all pending
dependencies being operated on by other threads have been flushed.
- Use softdep_waitidle() in unmount and snapshots to block either
operation until the fs is stable.
- Remove softdep worklist processing from the syncer and move it into the
softdep_flush() thread. This thread processes all softdep mounts
once each second and when it is called via the new softdep_speedup()
when there is a resource shortage. This removes the softdep hook
from the kernel and various hacks in header files to support it.
Reviewed by/Discussed with: tegge, truckman, mckusick
Tested by: kris
the directory's inode after queuing the dirrem that will decrement
the parent directory's link count. This will force the update of
the parent directory's actual link to actually be scheduled. Without
this change the parent directory's actual link count would not be
updated until ufs_inactive() cleared the inode of the newly removed
directory, which might be deferred indefinitely. ufs_inactive()
will not be called as long as any process holds a reference to the
removed directory, and ufs_inactive() will not clear the inode if
the link count is non-zero, which could be the result of an earlier
system crash.
If a background fsck is run before the update of the parent directory's
actual link count has been performed, or at least scheduled by
putting the dirrem on the leaf directory's inodedep id_bufwait list,
fsck will corrupt the file system by decrementing the parent
directory's effective link count, which was previously correct
because it already took the removal of the leaf directory into
account, and setting the actual link count to the same value as the
effective link count after the dangling, removed, leaf directory
has been removed. This happens because fsck acts based on the
actual link count, which will be too high when fsck creates the
file system snapshot that it references.
This change has the fortunate side effect of more quickly cleaning
up the large number dirrem structures that linger for an extended
time after the removal of a large directory tree. It also fixes a
potential problem with the shutdown of the syncer thread timing out
if the system is rebooted immediately after removing a large directory
tree.
Submitted by: tegge
MFC after: 3 days
Don't free a struct inodedep if another process is allocating saved inode
memory for the same struct inodedep in initiate_write_inodeblock_ufs[12]().
Handle disappearing dependencies in softdep_disk_io_initiation().
Reviewed by: mckusick
export. This was happening anyway since this file manually sets DEBUG.
- Add a sysctl for the number of items on the worklist.
- Use a more canonical loop restart in softdep_fsync_mountdev, it saves
some code at the expense of a goto and makes me worry less about
modifying a variable that should be private to the TAILQ_FOREACH_SAFE
macro.
two bugs.
- ffs_disk_prewrite was pulling the vp from the buf and checking for
COPYONWRITE, when really it wanted the vp from the bufobj that we're
writing to, which is the devvp. This lead to us skipping the copy on
write to all file data, which significantly broke snapshots for the
last few months.
- When the SOFTUPDATES option was not included in the kernel config we
would also skip the copy on write check, which would effectively disable
snapshots.
- Remove an invalid mp_fixme().
Debugging tips from: mckusick
Reported by: iedowse, others
Discussed with: phk
add more work are forced to process two worklist items first.
However, processing an item may generate additional work, causing the
unlucky thread to recursively process the worklist. Add a per-thread
flag to detect this situation and avoid the recursion. This should
fix the stack overflows that could occur while removing large
directory trees.
Tested by: kris
Reviewed by: mckusick
very slow process, especially for large file systems that is just
recovered from a crash.
Since the summary is already re-sync'ed every 30 second, we will
not lag behind too much after a crash. With this consideration
in mind, it is more reasonable to transfer the responsibility to
background fsck, to reduce the delay after a crash.
Add a new sysctl variable, vfs.ffs.compute_summary_at_mount, to
control this behavior. When set to nonzero, we will get the
"old" behavior, that the summary is computed immediately at mount
time.
Add five new sysctl variables to adjust ndir, nbfree, nifree,
nffree and numclusters respectively. Teach fsck_ffs about these
API, however, intentionally not to check the existence, since
kernels without these sysctls must have recomputed the summary
and hence no adjustments are necessary.
This change has eliminated the usual tens of minutes of delay of
mounting large dirty volumes.
Reviewed by: mckusick
MFC After: 1 week
Give FFS vnodes a specific bufwrite method which contains all the
background write stuff and then calls into the default bufwrite()
for the rest of the job.
Remove all the background write related stuff from the normal bufwrite.
This drags the softdep_move_dependencies() back into FFS.
Long term, it is worth looking at simply copying the data into
allocated memory and issuing the bio directly and not create the
"shadow buf" in the first place (just like copy-on-write is done
in snapshots for instance). I don't think we really gain anything
but complexity from doing this with a buf.
The "business class upgrade" was implemented in UFS's VOP_LOCK
implementation ufs_lock() which is the wrong layer, so move it to
ffs_lock().
Also, as long as we have not abandonned advanced vfs-stacking we
should not preclude it from happening: instead of implementing a
copy locally, use the VOP_LOCK_APV(&ufs) to correctly arrive at
vop_stdlock() at the bottom.
- Expand the scope of lk to cover not only interrupt races, but also
top-half races, which includes many new uses over global top-half
only data.
- Get rid of interlocked_sleep() and use msleep or BUF_LOCK where
appropriate.
- Use the lk mutex in place of the various hand rolled semaphores.
- Stop dropping the lk lock before we panic.
- Fix getdirtybuf() callers so that they reacquire access to whatever
softdep datastructure they were inxpecting in the failure/retry
case. Previously, sleeps in getdirtybuf() could leave us with
pointers to bad memory.
- Update handling of ffs to be compatible with ffs locking changes.
Sponsored By: Isilon Systems, Inc.
I'm not sure why a credential was added to these in the first place, it is
not used anywhere and it doesn't make much sense:
The credentials for syncing a file (ability to write to the
file) should be checked at the system call level.
Credentials for syncing one or more filesystems ("none")
should be checked at the system call level as well.
If the filesystem implementation needs a particular credential
to carry out the syncing it would logically have to the
cached mount credential, or a credential cached along with
any delayed write data.
Discussed with: rwatson
This eliminates a bunch of vnode overhead (approx 1-2 % speed
improvement) and gives us more control over the access to the storage
device.
Access counts on the underlying device are not correctly tracked and
therefore it is possible to read-only mount the same disk device multiple
times:
syv# mount -p
/dev/md0 /var ufs rw 2 2
/dev/ad0 /mnt ufs ro 1 1
/dev/ad0 /mnt2 ufs ro 1 1
/dev/ad0 /mnt3 ufs ro 1 1
Since UFS/FFS is not a synchrousely consistent filesystem (ie: it caches
things in RAM) this is not possible with read-write mounts, and the system
will correctly reject this.
Details:
Add a geom consumer and a bufobj pointer to ufsmount.
Eliminate the vnode argument from softdep_disk_prewrite().
Pick the vnode out of bp->b_vp for now. Eventually we
should find it through bp->b_bufobj->b_private.
In the mountcode, use g_vfs_open() once we have used
VOP_ACCESS() to check permissions.
When upgrading and downgrading between r/o and r/w do the
right thing with GEOM access counts. Remove all the
workarounds for not being able to do this with VOP_OPEN().
If we are the root mount, drop the exclusive access count
until we upgrade to r/w. This allows fsck of the root
filesystem and the MNT_RELOAD to work correctly.
Set bo_private to the GEOM consumer on the device bufobj.
Change the ffs_ops->strategy function to call g_vfs_strategy()
In ufs_strategy() directly call the strategy on the disk
bufobj. Same in rawread.
In ffs_fsync() we will no longer see VCHR device nodes, so
remove code which synced the filesystem mounted on it, in
case we came there. I'm not sure this code made sense in
the first place since we would have taken the specfs route
on such a vnode.
Redo the highly bogus readblock() function in the snapshot
code to something slightly less bogus: Constructing an uio
and using physio was really quite a detour. Instead just
fill in a bio and ship it down.
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.
is ffs_copyonwrite() and the only place it can be called from is FFS which
would never want to call another filesystems copyonwrite method, should one
exist, so there is no reason why anything generic should know about this.
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.
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.
AFTER the call to vn_start_write(), not before it. Otherwise, it is
possible to unlock it multiple times if the vn_start_write() fails.
Submitted by: Juergen Hannken-Illjes <hannken@eis.cs.tu-bs.de>
