When allocating a new inode, we need to make sure i_sync_tid and
i_datasync_tid are initialized. Otherwise, one or both of these two
values could be left initialized to zero, which could potentially
result in BUG_ON in jbd2_journal_commit_transaction.
(This could happen by having journal->commit_request getting set to
zero, which could wake up the kjournald process even though there is
no running transaction, which then causes a BUG_ON via the
J_ASSERT(j_ruinning_transaction != NULL) statement.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
While running ext4 testing on multiple core, we found there are per
cpu ext4-dio-unwritten threads processing conversion from unwritten
extents to written for IOs completed from async direct IO patch. Per
filesystem is enough, we don't need per cpu threads to work on
conversion.
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
If no extent conversion is required, wake up any processes waiting for
the page's writeback to be complete and free the ext4_io_end structure
directly in ext4_end_bio() instead of dropping it on the linked list
(which requires taking a spinlock to queue and dequeue the io_end
structure), and waiting for the workqueue to do this work.
This removes an extra scheduling delay before process waiting for an
fsync() to complete gets woken up, and it also reduces the CPU
overhead for a random write workload.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Orphan cleanup is currently executed even if the file system has some
number of unknown ROCOMPAT features, which deletes inodes and frees
blocks, which could be very bad for some RO_COMPAT features,
especially the SNAPSHOT feature.
This patch skips the orphan cleanup if it contains readonly compatible
features not known by this ext4 implementation, which would prevent
the fs from being mounted (or remounted) readwrite.
Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
nblocks is passed into ext4_truncate_restart_trans() from
ext4_ext_truncate_extend_restart() with a value different from the default
blocks_for_truncate(), but is being ignored.
The two other calls to ext4_truncate_restart_trans() already pass the
default value, which is then being recalculated inside the function.
Fix the problem by using the passed argument.
Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
This assures that the root inode is not leaked, and that sb->s_root is
NULL, which will prevent generic_shutdown_super() from doing extra
work, including call sync_filesystem, which ultimately results in
ext4_sync_fs() getting called with an uninitialized struct super,
which is the cause of the crash noted in Kernel Bugzilla #26752.
https://bugzilla.kernel.org/show_bug.cgi?id=26752
Signed-off-by: Manish Katiyar <mkatiyar@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Fix the FIEMAP ioctl so that it returns all of the page ranges which
are still subject to delayed allocation. We were missing some cases
if the file was sparse.
Reported by Chris Mason <chris.mason@oracle.com>:
>We've had reports on btrfs that cp is giving us files full of zeros
>instead of actually copying them. It was tracked down to a bug with
>the btrfs fiemap implementation where it was returning holes for
>delalloc ranges.
>
>Newer versions of cp are trusting fiemap to tell it where the holes
>are, which does seem like a pretty neat trick.
>
>I decided to give xfs and ext4 a shot with a few tests cases too, xfs
>passed with all the ones btrfs was getting wrong, and ext4 got the basic
>delalloc case right.
>$ mkfs.ext4 /dev/xxx
>$ mount /dev/xxx /mnt
>$ dd if=/dev/zero of=/mnt/foo bs=1M count=1
>$ fiemap-test foo
>ext: 0 logical: [ 0.. 255] phys: 0.. 255
>flags: 0x007 tot: 256
>
>Horray! But once we throw a hole in, things go bad:
>$ mkfs.ext4 /dev/xxx
>$ mount /dev/xxx /mnt
>$ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=1
>$ fiemap-test foo
>< no output >
>
>We've got a delalloc extent after the hole and ext4 fiemap didn't find
>it. If I run sync to kick the delalloc out:
>$sync
>$ fiemap-test foo
>ext: 0 logical: [ 256.. 511] phys: 34048.. 34303
>flags: 0x001 tot: 256
>
>fiemap-test is sitting in my /usr/local/bin, and I have no idea how it
>got there. It's full of pretty comments so I know it isn't mine, but
>you can grab it here:
>
>http://oss.oracle.com/~mason/fiemap-test.c
>
>xfsqa has a fiemap program too.
After Fix, test results are as follows:
ext: 0 logical: [ 256.. 511] phys: 0.. 255
flags: 0x007 tot: 256
ext: 0 logical: [ 256.. 511] phys: 33280.. 33535
flags: 0x001 tot: 256
$ mkfs.ext4 /dev/xxx
$ mount /dev/xxx /mnt
$ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=1
$ sync
$ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=3
$ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=5
$ fiemap-test foo
ext: 0 logical: [ 256.. 511] phys: 33280.. 33535
flags: 0x000 tot: 256
ext: 1 logical: [ 768.. 1023] phys: 0.. 255
flags: 0x006 tot: 256
ext: 2 logical: [ 1280.. 1535] phys: 0.. 255
flags: 0x007 tot: 256
Tested-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
If CONFIG_EXT4_DEBUG is enabled, then if a block allocation fails due
to disk being full, a verbose debugging message is printed, even if
the malloc-debug switch has not been enabled. Suppress the debugging
message so that nothing is printed unless malloc-debug has been turned
on.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
In ext4_bio_write_page(), if the memory allocation for the struct
ext4_io_page fails, it returns with the page's PageWriteback flag set.
This will end up causing the page not to skip writeback in
WB_SYNC_NONE mode, and in WB_SYNC_ALL mode (i.e., on a sync, fsync, or
umount) the writeback daemon will get stuck forever on the
wait_on_page_writeback() function in write_cache_pages_da().
Or, if journalling is enabled and the file gets deleted, it the
journal thread can get stuck in journal_finish_inode_data_buffers()
call to filemap_fdatawait().
Another place where things can get hung up is in
truncate_inode_pages(), called out of ext4_evict_inode().
Fix this by not setting PageWriteback until after we have successfully
allocated the struct ext4_io_page.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Move the initialization of all of the fields of the mpd structure to
write_cache_pages_da(). This simplifies the code considerably.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
If we have accumulated a contiguous region of memory to be written
out, and the next page can added to this region, don't bother locking
(and then unlocking the page) before writing out the memory. In the
unlikely event that the next page was being written back by some other
CPU, we can also skip waiting that page to finish writeback.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Because the ext4 page writeback codepath had been prematurely calling
clear_page_dirty_for_io(), if it turned out that a particular page
couldn't be written out during a particular pass of
write_cache_pages_da(), the page would have to get redirtied by
calling redirty_pages_for_writeback(). Not only was this wasted work,
but redirty_page_for_writeback() would increment wbc->pages_skipped to
signal to writeback_sb_inodes() that buffers were locked, and that it
should skip this inode until later.
Since this signal was incorrect in ext4's case --- which was caused by
ext4's historically incorrect use of write_cache_pages() ---
ext4_da_writepages() saved and restored wbc->skipped_pages to avoid
confusing writeback_sb_inodes().
Now that we've fixed ext4 to call clear_page_dirty_for_io() right
before initiating the page I/O, we can nuke the page_skipped
save/restore hackery, and breathe a sigh of relief.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Move when we call clear_page_dirty_for_io() to just before we actually
write the page. This simplifies the code somewhat, and avoids marking
pages as clean and then needing to remark them as dirty later.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Eliminate duplicate code, unneeded variables, etc., to make it easier
to understand the code. No behavioral changes were made in this patch.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Fold the __mpage_da_writepage() function into write_cache_pages_da().
This will give us opportunities to clean up and simplify the resulting
code.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Now that we've fixed the file corruption bug in commit d50bdd5aa5,
it's time to enable mblk_io_submit by default.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
If ext4_da_block_invalidatepages() is called because of a
failure from ext4_map_blocks() in mpage_da_map_and_submit(),
it's supposed to clean up -- including unlock -- all the
pages in the mpd structure. But these values may not match
up, even on a system in which block size == page size:
mpd->b_blocknr != mpd->first_page
mpd->b_size != (mpd->next_page - mpd->first_page)
ext4_da_block_invalidatepages() has been using b_blocknr and
b_size; this patch changes it to use first_page and
next_page.
Tested: I injected a small number (5%) of failures in
ext4_map_blocks() in the case that the flags contain
EXT4_GET_BLOCKS_DELALLOC_RESERVE, and ran fsstress on this
kernel. Without this patch, I got hung tasks every time.
With this patch, I see no hangs in many runs of fsstress.
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
In mpage_da_map_and_submit(), if we have a delayed block
allocation failure from ext4_map_blocks(), we need to mark
the IO as complete, by setting
mpd->io_done = 1;
Otherwise, we could end up submitting the pages in an outer
loop; since they are unlocked on mapping failure in
ext4_da_block_invalidatepages(), this will cause a bug check
in mpage_da_submit_io().
I tested this by injected failures into ext4_map_blocks().
Without this patch, a simple fsstress run will bug check;
with the patch, it works fine.
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
In ext4_mb_check_group_pa(), the current preallocation space is
replaced with a new preallocation space when the two have the same
distance from the goal block.
This doesn't actually gain us anything, so change things so that the
function only switches to the new preallocation group if its distance
from the goal block is strictly smaller than the current preallocaiton
group's distance from the goal block.
Signed-off-by: Coly Li <bosong.ly@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This patch adds comments to ext4_mb_mark_free_simple to make it more
understandable.
Signed-off-by: Coly Li <bosong.ly@taobao.com>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: Theodore Tso <tytso@google.com>
In __mb_check_buddy(), look at the code below:
591 fstart = -1;
592 buddy = mb_find_buddy(e4b, 0, &max);
593 for (i = 0; i < max; i++) {
594 if (!mb_test_bit(i, buddy)) {
595 MB_CHECK_ASSERT(i >= e4b->bd_info->bb_first_free);
596 if (fstart == -1) {
597 fragments++;
598 fstart = i;
599 }
600 continue;
601 }
602 fstart = -1;
603 /* check used bits only */
604 for (j = 0; j < e4b->bd_blkbits + 1; j++) {
605 buddy2 = mb_find_buddy(e4b, j, &max2);
606 k = i >> j;
607 MB_CHECK_ASSERT(k < max2);
608 MB_CHECK_ASSERT(mb_test_bit(k, buddy2));
609 }
610 }
611 MB_CHECK_ASSERT(!EXT4_MB_GRP_NEED_INIT(e4b->bd_info));
612 MB_CHECK_ASSERT(e4b->bd_info->bb_fragments == fragments);
613
614 grp = ext4_get_group_info(sb, e4b->bd_group);
615 buddy = mb_find_buddy(e4b, 0, &max);
On line 592, buddy is fetched by mb_find_buddy() with order 0, between
line 593 to line 615, buddy is not changed, therefore there is
no need to fetch buddy again from mb_find_buddy() with order 0 again.
We can safely remove the second mb_find_buddy() on line 615.
Signed-off-by: Coly Li <bosong.ly@taobao.com>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: Theodore Tso <tytso@google.com>
Current code calculate max no matter whether order is zero, it's
unnecessary. This cleanup patch sets max to "1 << (e4b->bd_blkbits
+ 3)" only when order == 0.
Signed-off-by: Coly Li <bosong.ly@taobao.com>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: Theodore Tso <tytso@google.com>
There's no good reason to require the extra step of providing
a mount option for acl or user_xattr once the feature is configured
on; no other filesystem that I know of requires this.
Userspace patches have set these options in default mount options,
and this patch makes them default in the kernel. At some point
we can start to deprecate the options, perhaps.
For now I've removed default mount option checks in show_options()
to be explicit about what's set, since it's changing the default,
but I'm open to alternatives if desired.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Discard granularity tells us the minimum size of extent that can be
discarded by the device. If the user supplies a minimum extent that
should be discarded (range.minlen) which is smaller than the discard
granularity, increase minlen to the discard granularity, since there's
no point submitting trim requests that the device will reject anyway.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
For a device that does not support discard, the FITRIM ioctl returns
-EOPNOTSUPP when blkdev_issue_discard() returns this error code, which
is how the user is informed that the device does not support discard.
If there are no suitable free extents to be trimmed, then FITRIM will
return success even though the device does not support discard, which
could confuse the user. So check explicitly if the device supports
discard and return an error code at the beginning of the FITRIM ioctl
processing.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
I cannot disable inode-read-ahead feature of ext4 (on 2.6.37):
# echo 0 > /sys/fs/ext4/sda2/inode_readahead_blks
bash: echo: write error: Invalid argument
On a server with lots of small files and random access this read-ahead makes
performance worse, and I'd like to disable it. I work around this problem
by using value of 1, but it still reads an extra block.
This patch fixes the problem by checking for zero explicitly.
Signed-off-by: Alexander V. Lukyanov <lav@netis.ru>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This patch fixes the warning "Using plain integer as NULL pointer",
generated by sparse, by replacing the offending 0s with NULL.
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Compile 2.6.38-rc1 with turning EXT4FS_DEBUG on,
we get following compile warnings. This patch fixes them.
CC fs/ext4/hash.o
CC fs/ext4/resize.o
fs/ext4/resize.c: In function 'setup_new_group_blocks':
fs/ext4/resize.c:233:2: warning: format '%#04llx' expects type 'long long
unsigned int', but argument 3 has type 'long unsigned int'
fs/ext4/resize.c:251:2: warning: format '%#04llx' expects type 'long long
unsigned int', but argument 3 has type 'long unsigned int'
CC fs/ext4/extents.o
CC fs/ext4/ext4_jbd2.o
CC fs/ext4/migrate.o
Reported-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Add documentation for mount options and ioctls to
Documentation/filesystem/ext4.txt, which has not been udpated for some
time. Also add for ext4 sysfs tunables to the
Documentation/ABI/testing/sysfs-fs-ext4 file, and fix a few
typographical errors in that file.
https://bugzilla.kernel.org/show_bug.cgi?id=9423
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
When Al moved the nameidata_dentry_drop_rcu_maybe() call into the
do_follow_link function in commit 844a391799 ("nothing in
do_follow_link() is going to see RCU"), he mistakenly left the
BUG_ON(inode != path->dentry->d_inode);
behind. Which would otherwise be ok, but that BUG_ON() really needs to
be _after_ dropping RCU, since the dentry isn't necessarily stable
otherwise.
So complete the code movement in that commit, and move the BUG_ON() into
do_follow_link() too. This means that we need to pass in 'inode' as an
argument (just for this one use), but that's a small thing. And
eventually we may be confident enough in our path lookup that we can
just remove the BUG_ON() and the unnecessary inode argument.
Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu:
m68knommu: set flow handler for secondary interrupt controller of 5249
m68knommu: remove use of IRQ_FLG_LOCK from 68360 platform support
m68knommu: fix dereference of port.tty
m68knommu: add missing linker __modver section
m68knommu: fix mis-named variable int set_irq_chip loop
m68knommu: add optimize memmove() function
m68k: remove arch specific non-optimized memcmp()
m68knommu: fix use of un-defined _TIF_WORK_MASK
m68knommu: Rename m548x_wdt.c to m54xx_wdt.c
m68knommu: fix m548x_wdt.c compilation after headers renaming
m68knommu: Remove dependencies on nonexistent M68KNOMMU
The secondary interrupt controller of the ColdFire 5249 code is not
setting the edge triggered flow handler. Set it.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
The struct_tty associated with a port is now a direct pointer
from within the local private driver info struct. So fix all uses
of it.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Compiling for 68360 targets gives:
CC arch/m68knommu/platform/68360/ints.o
arch/m68knommu/platform/68360/ints.c: In function ‘init_IRQ’:
arch/m68knommu/platform/68360/ints.c:135:16: error: ‘irq’ undeclared (first use in this function)
arch/m68knommu/platform/68360/ints.c:135:16: note: each undeclared identifier is reported only once for each function it appears in
Fix variable name used.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Add an m68k/coldfire optimized memmove() function for the m68knommu arch.
This is the same function as used by m68k. Simple speed tests show this
is faster once buffers are larger than 4 bytes, and significantly faster
on much larger buffers (4 times faster above about 100 bytes).
This also goes part of the way to fixing a regression caused by commit
ea61bc461d ("m68k/m68knommu: merge MMU and
non-MMU string.h"), which breaks non-coldfire non-mmu builds (which is
the 68x328 and 68360 families). They currently have no memmove() fucntion
defined, since there was none in the m68knommu/lib functions.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
The m68k arch implements its own memcmp() function. It is not optimized
in any way (it is the most strait forward coding of memcmp you can get).
Remove it and use the kernels standard memcmp() implementation.
This also goes part of the way to fixing a regression caused by commit
ea61bc461d ("m68k/m68knommu: merge MMU and
non-MMU string.h"), which breaks non-coldfire non-mmu builds (which is
the 68x328 and 68360 families). They currently have no memcmp() function
defined, since there is none in the m68knommu/lib functions.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
* 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6: (27 commits)
drm/radeon/kms: hopefully fix pll issues for real (v3)
drm/radeon/kms: add bounds checking to avivo pll algo
drm: fix wrong usages of drm_device in DRM Developer's Guide
drm/radeon/kms: fix a few more atombios endian issues
drm/radeon/kms: improve 6xx/7xx CS error output
drm/radeon/kms: check AA resolve registers on r300
drm/radeon/kms: fix tracking of BLENDCNTL, COLOR_CHANNEL_MASK, and GB_Z on r300
drm/radeon/kms: use linear aligned for evergreen/ni bo blits
drm/radeon/kms: use linear aligned for 6xx/7xx bo blits
drm/radeon: fix race between GPU reset and TTM delayed delete thread.
drm/radeon/kms: evergreen/ni big endian fixes (v2)
drm/radeon/kms: 6xx/7xx big endian fixes
drm/radeon/kms: atombios big endian fixes
drm/radeon: 6xx/7xx non-kms endian fixes
drm/radeon/kms: optimize CS state checking for r100->r500
drm: do not leak kernel addresses via /proc/dri/*/vma
drm/radeon/kms: add connector table for mac g5 9600
radeon mkregtable: Add missing fclose() calls
drm/radeon/kms: fix interlaced modes on dce4+
drm/radeon: fix memory debugging since d961db75ce
...
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6:
pci: use security_capable() when checking capablities during config space read
Transparent hugepages can only be created if rmap is fully
functional. So we must prevent hugepages to be created while
is_vma_temporary_stack() is true.
This also optmizes away some harmless but unnecessary setting of
khugepaged_scan.address and it switches some BUG_ON to VM_BUG_ON.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
ACPI / Video: Probe for output switch method when searching video devices.
ACPI / Wakeup: Enable button GPEs unconditionally during initialization
ACPI / ACPICA: Avoid crashing if _PRW is defined for the root object
ACPI: Fix acpi_os_read_memory() and acpi_os_write_memory() (v2)
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx: (21 commits)
dmaengine: add slave-dma maintainer
dma: ipu_idmac: do not lose valid received data in the irq handler
dmaengine: imx-sdma: fix up param for the last BD in sdma_prep_slave_sg()
dmaengine: imx-sdma: correct sdmac->status in sdma_handle_channel_loop()
dmaengine: imx-sdma: return sdmac->status in sdma_tx_status()
dmaengine: imx-sdma: set sdmac->status to DMA_ERROR in err_out of sdma_prep_slave_sg()
dmaengine: imx-sdma: remove IMX_DMA_SG_LOOP handling in sdma_prep_slave_sg()
dmaengine i.MX dma: initialize dma capabilities outside channel loop
dmaengine i.MX DMA: do not initialize chan_id field
dmaengine i.MX dma: check sg entries for valid addresses and lengths
dmaengine i.MX dma: set maximum segment size for our device
dmaengine i.MX SDMA: reserve channel 0 by not registering it
dmaengine i.MX SDMA: initialize dma capabilities outside channel loop
dmaengine i.MX SDMA: do not initialize chan_id field
dmaengine i.MX sdma: check sg entries for valid addresses and lengths
dmaengine i.MX sdma: set maximum segment size for our device
DMA: PL08x: fix channel pausing to timeout rather than lockup
DMA: PL08x: fix infinite wait when terminating transfers
dmaengine: imx-sdma: fix inconsistent naming in sdma_assign_cookie()
dmaengine: imx-sdma: propagate error in sdma_probe() instead of returning 0
...
* 'for-2.6.38' of git://linux-nfs.org/~bfields/linux:
nfsd: break lease on unlink due to rename
nfsd4: acquire only one lease per file
nfsd4: modify fi_delegations under recall_lock
nfsd4: remove unused deleg dprintk's.
nfsd4: split lease setting into separate function
nfsd4: fix leak on allocation error
nfsd4: add helper function for lease setup
nfsd4: split up nfsd_break_deleg_cb
NFSD: memory corruption due to writing beyond the stat array
NFSD: use nfserr for status after decode_cb_op_status
nfsd: don't leak dentry count on mnt_want_write failure
