Currently d_move(from, to) does the following:
* name/parent of from <- old name/parent of to, from hashed there
* to is unhashed
* name of to is preserved
* if from used to be detached, to gets detached
* if from used to be attached, parent of to <- old parent of from.
That's both user-visibly bogus and complicates reasoning a lot.
Much saner semantics would be
* name/parent of from <- name/parent of to, from hashed there.
* to is unhashed
* name/parent of to is unchanged.
The price, of course, is that old parent of from might lose a reference.
However,
* all potentially cross-directory callers of d_move() have both
parents pinned directly; typically, dentries themselves are grabbed
only after we have grabbed and locked both parents. IOW, the decrement
of old parent's refcount in case of d_move() won't reach zero.
* __d_move() from d_splice_alias() is done to detached alias.
No refcount decrements in that case
* __d_move() from __d_unalias() *can* get the refcount to zero.
So let's grab a reference to alias' old parent before calling __d_unalias()
and dput() it after we'd dropped rename_lock.
That does make d_splice_alias() potentially blocking. However, it has
no callers in non-sleepable contexts (and the case where we'd grown
that dget/dput pair is _very_ rare, so performance is not an issue).
Another thing that needs adjustment is unlocking in the end of __d_move();
folded it in. And cleaned the remnants of bogus ordering from the
"lock them in the beginning" counterpart - it's never been right and
now (well, for 7 years now) we have that thing always serialized on
rename_lock anyway.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
shrink_dentry_list() holds dentry->d_lock and needs to acquire
dentry->d_inode->i_lock. This cannot be done with a spin_lock()
operation because it's the reverse of the regular lock order.
To avoid ABBA deadlocks it is done with a trylock loop.
Trylock loops are problematic in two scenarios:
1) PREEMPT_RT converts spinlocks to 'sleeping' spinlocks, which are
preemptible. As a consequence the i_lock holder can be preempted
by a higher priority task. If that task executes the trylock loop
it will do so forever and live lock.
2) In virtual machines trylock loops are problematic as well. The
VCPU on which the i_lock holder runs can be scheduled out and a
task on a different VCPU can loop for a whole time slice. In the
worst case this can lead to starvation. Commits 47be61845c
("fs/dcache.c: avoid soft-lockup in dput()") and 046b961b45
("shrink_dentry_list(): take parent's d_lock earlier") are
addressing exactly those symptoms.
Avoid the trylock loop by using dentry_kill(). When pruning ancestors,
the same code applies that is used to kill a dentry in dput(). This
also has the benefit that the locking order is now the same. First
the inode is locked, then the parent.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In case when trylock in there fails, deal with it directly in
dentry_kill(). Note that in cases when we drop and retake
->d_lock, we need to recheck whether to retain the dentry.
Another thing is that dropping/retaking ->d_lock might have
ended up with negative dentry turning into positive; that,
of course, can happen only once...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In case of trylock failure don't re-add to the list - drop the locks
and carefully get them in the right order. For shrink_dentry_list(),
somebody having grabbed a reference to dentry means that we can
kick it off-list, so if we find dentry being modified under us we
don't need to play silly buggers with retries anyway - off the list
it is.
The locking logics taken out into a helper of its own; lock_parent()
is no longer used for dentries that can be killed under us.
[fix from Eric Biggers folded]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
A subsequent patch will modify dentry_kill() to call lock_parent().
Move the dentry_kill() implementation "as is" below lock_parent()
first. This will help simplify the review of the subsequent patch
with dentry_kill() changes.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Commit 0d98439ea3 ("vfs: use lockred "dead" flag to mark unrecoverably
dead dentries") removed the `ref' parameter in dentry_kill() but its
documentation remained. Remove it.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
i_dir_seq is subject to concurrent modification by a cmpxchg or
store-release operation, so ensure that the relaxed access in
d_alloc_parallel uses READ_ONCE.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If d_alloc_parallel runs concurrently with __d_add, it is possible for
d_alloc_parallel to continuously retry whilst i_dir_seq has been
incremented to an odd value by __d_add:
CPU0:
__d_add
n = start_dir_add(dir);
cmpxchg(&dir->i_dir_seq, n, n + 1) == n
CPU1:
d_alloc_parallel
retry:
seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
hlist_bl_lock(b);
bit_spin_lock(0, (unsigned long *)b); // Always succeeds
CPU0:
__d_lookup_done(dentry)
hlist_bl_lock
bit_spin_lock(0, (unsigned long *)b); // Never succeeds
CPU1:
if (unlikely(parent->d_inode->i_dir_seq != seq)) {
hlist_bl_unlock(b);
goto retry;
}
Since the simple bit_spin_lock used to implement hlist_bl_lock does not
provide any fairness guarantees, then CPU1 can starve CPU0 of the lock
and prevent it from reaching end_dir_add(dir), therefore CPU1 cannot
exit its retry loop because the sequence number always has the bottom
bit set.
This patch resolves the livelock by not taking hlist_bl_lock in
d_alloc_parallel if the sequence counter is odd, since any subsequent
masked comparison with i_dir_seq will fail anyway.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Naresh Madhusudana <naresh.madhusudana@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In case when dentry passed to lock_parent() is protected from freeing only
by the fact that it's on a shrink list and trylock of parent fails, we
could get hit by __dentry_kill() (and subsequent dentry_kill(parent))
between unlocking dentry and locking presumed parent. We need to recheck
that dentry is alive once we lock both it and parent *and* postpone
rcu_read_unlock() until after that point. Otherwise we could return
a pointer to struct dentry that already is rcu-scheduled for freeing, with
->d_lock held on it; caller's subsequent attempt to unlock it can end
up with memory corruption.
Cc: stable@vger.kernel.org # 3.12+, counting backports
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull x86 Kconfig fixes from Thomas Gleixner:
"Three patchlets to correct HIGHMEM64G and CMPXCHG64 dependencies in
Kconfig when CPU selections are explicitely set to M586 or M686"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/Kconfig: Explicitly enumerate i686-class CPUs in Kconfig
x86/Kconfig: Exclude i586-class CPUs lacking PAE support from the HIGHMEM64G Kconfig group
x86/Kconfig: Add missing i586-class CPUs to the X86_CMPXCHG64 Kconfig group
Pull perf updates from Thomas Gleixner:
"Perf tool updates and kprobe fixes:
- perf_mmap overwrite mode fixes/overhaul, prep work to get 'perf
top' using it, making it bearable to use it in large core count
systems such as Knights Landing/Mill Intel systems (Kan Liang)
- s/390 now uses syscall.tbl, just like x86-64 to generate the
syscall table id -> string tables used by 'perf trace' (Hendrik
Brueckner)
- Use strtoull() instead of home grown function (Andy Shevchenko)
- Synchronize kernel ABI headers, v4.16-rc1 (Ingo Molnar)
- Document missing 'perf data --force' option (Sangwon Hong)
- Add perf vendor JSON metrics for ARM Cortex-A53 Processor (William
Cohen)
- Improve error handling and error propagation of ftrace based
kprobes so failures when installing kprobes are not silently
ignored and create disfunctional tracepoints"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
kprobes: Propagate error from disarm_kprobe_ftrace()
kprobes: Propagate error from arm_kprobe_ftrace()
Revert "tools include s390: Grab a copy of arch/s390/include/uapi/asm/unistd.h"
perf s390: Rework system call table creation by using syscall.tbl
perf s390: Grab a copy of arch/s390/kernel/syscall/syscall.tbl
tools/headers: Synchronize kernel ABI headers, v4.16-rc1
perf test: Fix test trace+probe_libc_inet_pton.sh for s390x
perf data: Document missing --force option
perf tools: Substitute yet another strtoull()
perf top: Check the latency of perf_top__mmap_read()
perf top: Switch default mode to overwrite mode
perf top: Remove lost events checking
perf hists browser: Add parameter to disable lost event warning
perf top: Add overwrite fall back
perf evsel: Expose the perf_missing_features struct
perf top: Check per-event overwrite term
perf mmap: Discard legacy interface for mmap read
perf test: Update mmap read functions for backward-ring-buffer test
perf mmap: Introduce perf_mmap__read_event()
perf mmap: Introduce perf_mmap__read_done()
...
Pull irq updates from Thomas Gleixner:
"A small set of updates mostly for irq chip drivers:
- MIPS GIC fix for spurious, masked interrupts
- fix for a subtle IPI bug in GICv3
- do not probe GICv3 ITSs that are marked as disabled
- multi-MSI support for GICv2m
- various small cleanups"
* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqdomain: Re-use DEFINE_SHOW_ATTRIBUTE() macro
irqchip/bcm: Remove hashed address printing
irqchip/gic-v2m: Add PCI Multi-MSI support
irqchip/gic-v3: Ignore disabled ITS nodes
irqchip/gic-v3: Use wmb() instead of smb_wmb() in gic_raise_softirq()
irqchip/gic-v3: Change pr_debug message to pr_devel
irqchip/mips-gic: Avoid spuriously handling masked interrupts
Pull core fix from Thomas Gleixner:
"A small fix which adds the missing for_each_cpu_wrap() stub for the UP
case to avoid build failures"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpumask: Make for_each_cpu_wrap() available on UP as well
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Merge tag 'for-linus-20180217' of git://git.kernel.dk/linux-block
Pull block fixes from Jens Axboe:
- NVMe pull request from Keith, with fixes all over the map for nvme.
From various folks.
- Classic polling fix, that avoids a latency issue where we still end
up waiting for an interrupt in some cases. From Nitesh Shetty.
- Comment typo fix from Minwoo Im.
* tag 'for-linus-20180217' of git://git.kernel.dk/linux-block:
block: fix a typo in comment of BLK_MQ_POLL_STATS_BKTS
nvme-rdma: fix sysfs invoked reset_ctrl error flow
nvmet: Change return code of discard command if not supported
nvme-pci: Fix timeouts in connecting state
nvme-pci: Remap CMB SQ entries on every controller reset
nvme: fix the deadlock in nvme_update_formats
blk: optimization for classic polling
nvme: Don't use a stack buffer for keep-alive command
nvme_fc: cleanup io completion
nvme_fc: correct abort race condition on resets
nvme: Fix discard buffer overrun
nvme: delete NVME_CTRL_LIVE --> NVME_CTRL_CONNECTING transition
nvme-rdma: use NVME_CTRL_CONNECTING state to mark init process
nvme: rename NVME_CTRL_RECONNECTING state to NVME_CTRL_CONNECTING
- meson-gx: Revert to earlier tuning process
- bcm2835: Don't overwrite max frequency unconditionally
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Merge tag 'mmc-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
Pull MMC fixes from Ulf Hansson:
- meson-gx: Revert to earlier tuning process
- bcm2835: Don't overwrite max frequency unconditionally
* tag 'mmc-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
mmc: bcm2835: Don't overwrite max frequency unconditionally
Revert "mmc: meson-gx: include tx phase in the tuning process"
* Use the appropriate OOB layout in the VF610 driver
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Merge tag 'mtd/fixes-for-4.16-rc2' of git://git.infradead.org/linux-mtd
Pull mtd fixes from Boris Brezillon:
- add missing dependency to NAND_MARVELL Kconfig entry
- use the appropriate OOB layout in the VF610 driver
* tag 'mtd/fixes-for-4.16-rc2' of git://git.infradead.org/linux-mtd:
mtd: nand: MTD_NAND_MARVELL should depend on HAS_DMA
mtd: nand: vf610: set correct ooblayout
The main attraction is a fix for a bug in the new drmem code, which was causing
an oops on boot on some versions of Qemu.
There's also a fix for XIVE (Power9 interrupt controller) on KVM, as well as a
few other minor fixes.
Thanks to:
Corentin Labbe, Cyril Bur, Cédric Le Goater, Daniel Black, Nathan Fontenot,
Nicholas Piggin.
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Merge tag 'powerpc-4.16-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fixes from Michael Ellerman:
"The main attraction is a fix for a bug in the new drmem code, which
was causing an oops on boot on some versions of Qemu.
There's also a fix for XIVE (Power9 interrupt controller) on KVM, as
well as a few other minor fixes.
Thanks to: Corentin Labbe, Cyril Bur, Cédric Le Goater, Daniel Black,
Nathan Fontenot, Nicholas Piggin"
* tag 'powerpc-4.16-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/pseries: Check for zero filled ibm,dynamic-memory property
powerpc/pseries: Add empty update_numa_cpu_lookup_table() for NUMA=n
powerpc/powernv: IMC fix out of bounds memory access at shutdown
powerpc/xive: Use hw CPU ids when configuring the CPU queues
powerpc: Expose TSCR via sysfs only on powernv
- Updated the page table accessors to use READ/WRITE_ONCE and prevent
compiler transformation that could lead to an apparent loss of
coherency
- Enabled branch predictor hardening for the Falkor CPU
- Fix interaction between kpti enabling and KASan causing the recursive
page table walking to take a significant time
- Fix some sparse warnings
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 fixes from Catalin Marinas:
"The bulk of this is the pte accessors annotation to READ/WRITE_ONCE
(we tried to avoid pushing this during the merge window to avoid
conflicts)
- Updated the page table accessors to use READ/WRITE_ONCE and prevent
compiler transformation that could lead to an apparent loss of
coherency
- Enabled branch predictor hardening for the Falkor CPU
- Fix interaction between kpti enabling and KASan causing the
recursive page table walking to take a significant time
- Fix some sparse warnings"
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: cputype: Silence Sparse warnings
arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables
arm64: proc: Set PTE_NG for table entries to avoid traversing them twice
arm64: Add missing Falkor part number for branch predictor hardening
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Merge tag 'for-linus-4.16a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen fixes from Juergen Gross:
- fixes for the Xen pvcalls frontend driver
- fix for booting Xen pv domains
- fix for the xenbus driver user interface
* tag 'for-linus-4.16a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
pvcalls-front: wait for other operations to return when release passive sockets
pvcalls-front: introduce a per sock_mapping refcount
x86/xen: Calculate __max_logical_packages on PV domains
xenbus: track caller request id
Passive sockets can have ongoing operations on them, specifically, we
have two wait_event_interruptable calls in pvcalls_front_accept.
Add two wake_up calls in pvcalls_front_release, then wait for the
potential waiters to return and release the sock_mapping refcount.
Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Introduce a per sock_mapping refcount, in addition to the existing
global refcount. Thanks to the sock_mapping refcount, we can safely wait
for it to be 1 in pvcalls_front_release before freeing an active socket,
instead of waiting for the global refcount to be 1.
Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Commit fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent
xenstore accesses") optimized xenbus concurrent accesses but in doing so
broke UABI of /dev/xen/xenbus. Through /dev/xen/xenbus applications are in
charge of xenbus message exchange with the correct header and body. Now,
after the mentioned commit the replies received by application will no
longer have the header req_id echoed back as it was on request (see
specification below for reference), because that particular field is being
overwritten by kernel.
struct xsd_sockmsg
{
uint32_t type; /* XS_??? */
uint32_t req_id;/* Request identifier, echoed in daemon's response. */
uint32_t tx_id; /* Transaction id (0 if not related to a transaction). */
uint32_t len; /* Length of data following this. */
/* Generally followed by nul-terminated string(s). */
};
Before there was only one request at a time so req_id could simply be
forwarded back and forth. To allow simultaneous requests we need a
different req_id for each message thus kernel keeps a monotonic increasing
counter for this field and is written on every request irrespective of
userspace value.
Forwarding again the req_id on userspace requests is not a solution because
we would open the possibility of userspace-generated req_id colliding with
kernel ones. So this patch instead takes another route which is to
artificially keep user req_id while keeping the xenbus logic as is. We do
that by saving the original req_id before xs_send(), use the private kernel
counter as req_id and then once reply comes and was validated, we restore
back the original req_id.
Cc: <stable@vger.kernel.org> # 4.11
Fixes: fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
Reported-by: Bhavesh Davda <bhavesh.davda@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Sparse makes a fair bit of noise about our MPIDR mask being implicitly
long - let's explicitly describe it as such rather than just relying on
the value forcing automatic promotion.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Merge tag 'dma-mapping-4.16-2' of git://git.infradead.org/users/hch/dma-mapping
Pull dma-mapping fixes from Christoph Hellwig:
"A few dma-mapping fixes for the fallout from the changes in rc1"
* tag 'dma-mapping-4.16-2' of git://git.infradead.org/users/hch/dma-mapping:
powerpc/macio: set a proper dma_coherent_mask
dma-mapping: fix a comment typo
dma-direct: comment the dma_direct_free calling convention
dma-direct: mark as is_phys
ia64: fix build failure with CONFIG_SWIOTLB
In many cases, page tables can be accessed concurrently by either another
CPU (due to things like fast gup) or by the hardware page table walker
itself, which may set access/dirty bits. In such cases, it is important
to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
entries cannot be torn, merged or subject to apparent loss of coherence
due to compiler transformations.
Whilst there are some scenarios where this cannot happen (e.g. pinned
kernel mappings for the linear region), the overhead of using READ_ONCE
/WRITE_ONCE everywhere is minimal and makes the code an awful lot easier
to reason about. This patch consistently uses these macros in the arch
code, as well as explicitly namespacing pointers to page table entries
from the entries themselves by using adopting a 'p' suffix for the former
(as is sometimes used elsewhere in the kernel source).
Tested-by: Yury Norov <ynorov@caviumnetworks.com>
Tested-by: Richard Ruigrok <rruigrok@codeaurora.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
We get a warning about some slow configurations in randconfig kernels:
mm/memory.c:83:2: error: #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid. [-Werror=cpp]
The warning is reasonable by itself, but gets in the way of randconfig
build testing, so I'm hiding it whenever CONFIG_COMPILE_TEST is set.
The warning was added in 2013 in commit 75980e97da ("mm: fold
page->_last_nid into page->flags where possible").
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A few fixes for outstanding MIPS issues:
- An __init section mismatch warning when brcmstb_pm is enabled.
- A regression handling multiple mem=X@Y arguments (4.11).
- A USB Kconfig select warning, and related sparc cleanup (4.16).
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Merge tag 'mips_fixes_4.16_2' of git://git.kernel.org/pub/scm/linux/kernel/git/jhogan/mips
Pull MIPS fixes from James Hogan:
"A few fixes for outstanding MIPS issues:
- an __init section mismatch warning when brcmstb_pm is enabled
- a regression handling multiple mem=X@Y arguments (4.11)
- a USB Kconfig select warning, and related sparc cleanup (4.16)"
* tag 'mips_fixes_4.16_2' of git://git.kernel.org/pub/scm/linux/kernel/git/jhogan/mips:
sparc,leon: Select USB_UHCI_BIG_ENDIAN_{MMIO,DESC}
usb: Move USB_UHCI_BIG_ENDIAN_* out of USB_SUPPORT
MIPS: Fix incorrect mem=X@Y handling
MIPS: BMIPS: Fix section mismatch warning
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Merge tag 'for-4.16-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
"We have a few assorted fixes, some of them show up during fstests so I
gave them more testing"
* tag 'for-4.16-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: Fix use-after-free when cleaning up fs_devs with a single stale device
Btrfs: fix null pointer dereference when replacing missing device
btrfs: remove spurious WARN_ON(ref->count < 0) in find_parent_nodes
btrfs: Ignore errors from btrfs_qgroup_trace_extent_post
Btrfs: fix unexpected -EEXIST when creating new inode
Btrfs: fix use-after-free on root->orphan_block_rsv
Btrfs: fix btrfs_evict_inode to handle abnormal inodes correctly
Btrfs: fix extent state leak from tree log
Btrfs: fix crash due to not cleaning up tree log block's dirty bits
Btrfs: fix deadlock in run_delalloc_nocow
non-zero error with 0). This is particularly important given DM
core's increased use of chained bios.
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Merge tag 'for-4.16/dm-chained-bios-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper fix from Mike Snitzer:
"Fix for DM core to properly propagate errors (avoids overriding
non-zero error with 0). This is particularly important given DM core's
increased use of chained bios"
* tag 'for-4.16/dm-chained-bios-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm: correctly handle chained bios in dec_pending()
Al Viro