commit <249fad734a> ""powerpc/perf: Disable trace_imc pmu"
disables IMC(In-Memory Collection) trace-mode in kernel, since frequent
mode switching between accumulation mode and trace mode via the spr LDBAR
in the hardware can trigger a checkstop(system crash).
Patch to re-enable imc-trace mode in kernel.
The previous patch(1/2) in this series will address the mode switching issue
by implementing a global lock, and will restrict the usage of
accumulation and trace-mode at a time.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200313055238.8656-2-anju@linux.vnet.ibm.com
IMC(In-memory Collection Counters) does performance monitoring in
two different modes, i.e accumulation mode(core-imc and thread-imc events),
and trace mode(trace-imc events). A cpu thread can either be in
accumulation-mode or trace-mode at a time and this is done via the LDBAR
register in POWER architecture. The current design does not address the
races between thread-imc and trace-imc events.
Patch implements a global id and lock to avoid the races between
core, trace and thread imc events. With this global id-lock
implementation, the system can either run core, thread or trace imc
events at a time. i.e. to run any core-imc events, thread/trace imc events
should not be enabled/monitored.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200313055238.8656-1-anju@linux.vnet.ibm.com
MCE handling on pSeries platform fails as recent rework to use common
code for pSeries and PowerNV in machine check error handling tries to
access per-cpu variables in realmode. The per-cpu variables may be
outside the RMO region on pSeries platform and needs translation to be
enabled for access. Just moving these per-cpu variable into RMO region
did'nt help because we queue some work to workqueues in real mode, which
again tries to touch per-cpu variables. Also fwnmi_release_errinfo()
cannot be called when translation is not enabled.
This patch fixes this by enabling translation in the exception handler
when all required real mode handling is done. This change only affects
the pSeries platform.
Without this fix below kernel crash is seen on injecting
SLB multihit:
BUG: Unable to handle kernel data access on read at 0xc00000027b205950
Faulting instruction address: 0xc00000000003b7e0
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
Modules linked in: mcetest_slb(OE+) af_packet(E) xt_tcpudp(E) ip6t_rpfilter(E) ip6t_REJECT(E) ipt_REJECT(E) xt_conntrack(E) ip_set(E) nfnetlink(E) ebtable_nat(E) ebtable_broute(E) ip6table_nat(E) ip6table_mangle(E) ip6table_raw(E) ip6table_security(E) iptable_nat(E) nf_nat(E) nf_conntrack(E) nf_defrag_ipv6(E) nf_defrag_ipv4(E) iptable_mangle(E) iptable_raw(E) iptable_security(E) ebtable_filter(E) ebtables(E) ip6table_filter(E) ip6_tables(E) iptable_filter(E) ip_tables(E) x_tables(E) xfs(E) ibmveth(E) vmx_crypto(E) gf128mul(E) uio_pdrv_genirq(E) uio(E) crct10dif_vpmsum(E) rtc_generic(E) btrfs(E) libcrc32c(E) xor(E) zstd_decompress(E) zstd_compress(E) raid6_pq(E) sr_mod(E) sd_mod(E) cdrom(E) ibmvscsi(E) scsi_transport_srp(E) crc32c_vpmsum(E) dm_mod(E) sg(E) scsi_mod(E)
CPU: 34 PID: 8154 Comm: insmod Kdump: loaded Tainted: G OE 5.5.0-mahesh #1
NIP: c00000000003b7e0 LR: c0000000000f2218 CTR: 0000000000000000
REGS: c000000007dcb960 TRAP: 0300 Tainted: G OE (5.5.0-mahesh)
MSR: 8000000000001003 <SF,ME,RI,LE> CR: 28002428 XER: 20040000
CFAR: c0000000000f2214 DAR: c00000027b205950 DSISR: 40000000 IRQMASK: 0
GPR00: c0000000000f2218 c000000007dcbbf0 c000000001544800 c000000007dcbd70
GPR04: 0000000000000001 c000000007dcbc98 c008000000d00258 c0080000011c0000
GPR08: 0000000000000000 0000000300000003 c000000001035950 0000000003000048
GPR12: 000000027a1d0000 c000000007f9c000 0000000000000558 0000000000000000
GPR16: 0000000000000540 c008000001110000 c008000001110540 0000000000000000
GPR20: c00000000022af10 c00000025480fd70 c008000001280000 c00000004bfbb300
GPR24: c000000001442330 c00800000800000d c008000008000000 4009287a77000510
GPR28: 0000000000000000 0000000000000002 c000000001033d30 0000000000000001
NIP [c00000000003b7e0] save_mce_event+0x30/0x240
LR [c0000000000f2218] pseries_machine_check_realmode+0x2c8/0x4f0
Call Trace:
Instruction dump:
3c4c0151 38429050 7c0802a6 60000000 fbc1fff0 fbe1fff8 f821ffd1 3d42ffaf
3fc2ffaf e98d0030 394a1150 3bdef530 <7d6a62aa> 1d2b0048 2f8b0063 380b0001
---[ end trace 46fd63f36bbdd940 ]---
Fixes: 9ca766f989 ("powerpc/64s/pseries: machine check convert to use common event code")
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200320110119.10207-1-ganeshgr@linux.ibm.com
The ahci driver doesn't support error recovery, and if your root
filesystem is attached to it the eeh-basic.sh test will likely kill
your machine.
So skip any device we see using the ahci driver.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200326061144.2006522-1-mpe@ellerman.id.au
Commit 3282a3da25 ("powerpc/64: Implement soft interrupt replay in C")
broke the doorbell wakeup optimisation introduced by commit a9af97aa0a
("powerpc/64s: msgclr when handling doorbell exceptions from system
reset").
This patch restores the msgclr, in C code. It's now done in the system
reset wakeup path rather than doorbell interrupt replay where it used
to be, because it is always the right thing to do in the wakeup case,
but it may be rarely of use in other interrupt replay situations in
which case it's wasted work - we would have to run measurements to see
if that was a worthwhile optimisation, and I suspect it would not be.
The results are similar to those in the original commit, test on POWER8
of context_switch selftests benchmark with polling idle disabled (e.g.,
always nap, giving cross-CPU IPIs) gives the following results:
broken patched
Different threads, same core: 317k/s 375k/s +18.7%
Different cores: 280k/s 282k/s +1.0%
Fixes: 3282a3da25 ("powerpc/64: Implement soft interrupt replay in C")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200402121212.1118218-1-npiggin@gmail.com
The zte driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-23-tzimmermann@suse.de
The vkms driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-21-tzimmermann@suse.de
The virtgpu driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-20-tzimmermann@suse.de
The vc4 driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-19-tzimmermann@suse.de
The tilcdc driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Jyri Sarha <jsarha@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-18-tzimmermann@suse.de
The tidss driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Jyri Sarha <jsarha@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-17-tzimmermann@suse.de
The tegra driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-16-tzimmermann@suse.de
The ingenic driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-15-tzimmermann@suse.de
The shmobile driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-14-tzimmermann@suse.de
The rockchip driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-13-tzimmermann@suse.de
The rcar-du driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-12-tzimmermann@suse.de
The mediatek driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-11-tzimmermann@suse.de
The ingenic driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-10-tzimmermann@suse.de
The imx driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-9-tzimmermann@suse.de
The tda998x driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-8-tzimmermann@suse.de
The kirin driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-7-tzimmermann@suse.de
The gma500 driver uses empty implementations for some of its encoders.
Replace the code with the generic simple encoder. As a side effect, the
patch also removes an indirection in the encoder setup for Medfield.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-6-tzimmermann@suse.de
The fsl-dcu driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-5-tzimmermann@suse.de
The exynos driver uses empty implementations for its encoders. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-4-tzimmermann@suse.de
The atmel-hlcdc driver uses an empty implementation for its encoder.
Replace the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-3-tzimmermann@suse.de
Lockdep is needed by proving the spinlocks and rwlocks. Currently,
we only put trace_hardirqs_on/off with csky_irq and
ret_from_exception.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
When item release is called, the parent is already null. We need the
parent to pass to nvmet_referral_disable so hook it up to
->disconnect_notify.
Reported-by: Tony Asleson <tasleson@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
If the backing device require stable pages, we need to set it on the
stack mpath device as well. This applies to rdma/fc transports when
doing data integrity and tcp transport calculating digests.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This reverts commit 0f5cb8cc27.
This commit will cause below warnings, since our EIC controller can support
differnt banks on different Spreadtrum SoCs, and each bank has its own base
address, we will get invalid resource warning if the bank number is less than
SPRD_EIC_MAX_BANK on some Spreadtrum SoCs.
So we should not use devm_platform_ioremap_resource() here to remove the
warnings.
[ 1.118508] sprd-eic 40210000.gpio: invalid resource
[ 1.118535] sprd-eic 40210000.gpio: invalid resource
[ 1.119034] sprd-eic 40210080.gpio: invalid resource
[ 1.119055] sprd-eic 40210080.gpio: invalid resource
[ 1.119462] sprd-eic 402100a0.gpio: invalid resource
[ 1.119482] sprd-eic 402100a0.gpio: invalid resource
[ 1.119893] sprd-eic 402100c0.gpio: invalid resource
[ 1.119913] sprd-eic 402100c0.gpio: invalid resource
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/8d3579f4b49bb675dc805035960f24852898be28.1585734060.git.baolin.wang7@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The gpiochip_generic_request() and gpiochip_generic_free() functions can
now deal properly with chips that don't have any pin-ranges defined, so
they can be assigned unconditionally.
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20200401200527.2982450-2-thierry.reding@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The gpiochip_generic_request() and gpiochip_generic_free() functions can
now deal properly with chips that don't have any pin-ranges defined, so
they can be assigned unconditionally.
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20200401200527.2982450-1-thierry.reding@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
To improve security, always give the user-space daemon a chance to
accept or reject a Just Works pairing (LE). The daemon may decide to
auto-accept based on the user's intent.
Signed-off-by: Sonny Sasaka <sonnysasaka@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This adds BT_MODE socket option which can be used to set L2CAP modes,
including modes only supported over LE which were not supported using
the L2CAP_OPTIONS.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
L2CAP_OPTIONS shall only be used with BR/EDR modes.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This patch adds support for QCA6390, including the devicetree and acpi
compatible hwid matching, and patch/nvm downloading.
Signed-off-by: Rocky Liao <rjliao@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
We fall back to lookup+create (instead of atomic_open) in several cases:
1) we don't have write access to filesystem and O_TRUNC is
present in the flags. It's not something we want ->atomic_open() to
see - it just might go ahead and truncate the file. However, we can
pass it the flags sans O_TRUNC - eventually do_open() will call
handle_truncate() anyway.
2) we have O_CREAT | O_EXCL and we can't write to parent.
That's going to be an error, of course, but we want to know _which_
error should that be - might be EEXIST (if file exists), might be
EACCES or EROFS. Simply stripping O_CREAT (and checking if we see
ENOENT) would suffice, if not for O_EXCL. However, we used to have
->atomic_open() fully responsible for rejecting O_CREAT | O_EXCL
on existing file and just stripping O_CREAT would've disarmed
those checks. With nothing downstream to catch the problem -
FMODE_OPENED used to be "don't bother with EEXIST checks,
->atomic_open() has done those". Now EEXIST checks downstream
are skipped only if FMODE_CREATED is set - FMODE_OPENED alone
is not enough. That has eliminated the need to fall back onto
lookup+create path in this case.
3) O_WRONLY or O_RDWR when we have no write access to
filesystem, with nothing else objectionable. Fallback is
(and had always been) pointless.
IOW, we don't really need that fallback; all we need in such
cases is to trim O_TRUNC and O_CREAT properly.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
argument had been unused since 1643b43fbd (lookup_open(): lift the
"fallback to !O_CREAT" logics from atomic_open()) back in 2016
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently path_openat() has "EEXIST on O_EXCL|O_CREAT" checks done on one
of the ways out of open_last_lookups(). There are 4 cases:
1) the last component is . or ..; check is not done.
2) we had FMODE_OPENED or FMODE_CREATED set while in lookup_open();
check is not done.
3) symlink to be traversed is found; check is not done (nor
should it be)
4) everything else: check done (before complete_walk(), even).
In case (1) O_EXCL|O_CREAT ends up failing with -EISDIR - that's
open("/tmp/.", O_CREAT|O_EXCL, 0600)
Note that in the same conditions
open("/tmp", O_CREAT|O_EXCL, 0600)
would have yielded EEXIST. Either error is allowed, switching to -EEXIST
in these cases would've been more consistent.
Case (2) is more subtle; first of all, if we have FMODE_CREATED set, the
object hadn't existed prior to the call. The check should not be done in
such a case. The rest is problematic, though - we have
FMODE_OPENED set (i.e. it went through ->atomic_open() and got
successfully opened there)
FMODE_CREATED is *NOT* set
O_CREAT and O_EXCL are both set.
Any such case is a bug - either we failed to set FMODE_CREATED when we
had, in fact, created an object (no such instances in the tree) or
we have opened a pre-existing file despite having had both O_CREAT and
O_EXCL passed. One of those was, in fact caught (and fixed) while
sorting out this mess (gfs2 on cold dcache). And in such situations
we should fail with EEXIST.
Note that for (1) and (4) FMODE_CREATED is not set - for (1) there's nothing
in handle_dots() to set it, for (4) we'd explicitly checked that.
And (1), (2) and (4) are exactly the cases when we leave the loop in
the caller, with do_open() called immediately after that loop. IOW, we
can move the check over there, and make it
If we have O_CREAT|O_EXCL and after successful pathname resolution
FMODE_CREATED is *not* set, we must have run into a preexisting file and
should fail with EEXIST.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
now we can have open_last_lookups() directly from the loop in
path_openat() - the rest of do_last() never returns a symlink
to follow, so we can bloody well leave the loop first.
Rename the rest of that thing from do_last() to do_open() and
make it return an int.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
pick_link() needs to push onto stack; we start with using two-element
array embedded into struct nameidata and the first time we need
more than that we switch to separately allocated array.
Allocation can fail, of course, and handling of that would be simple
enough - we need to drop 'link' and bugger off. However, the things
get more complicated in RCU mode. There we must do GFP_ATOMIC
allocation. If that fails, we try to switch to non-RCU mode and
repeat the allocation.
To switch to non-RCU mode we need to grab references to 'link' and
to everything in nameidata. The latter done by unlazy_walk();
the former - legitimize_path(). 'link' must go first - after
unlazy_walk() we are out of RCU-critical period and it's too
late to call legitimize_path() since the references in link->mnt
and link->dentry might be pointing to freed and reused memory.
So we do legitimize_path(), then unlazy_walk(). And that's where
it gets too subtle: what to do if the former fails? We MUST
do path_put(link) to avoid leaks. And we can't do that under
rcu_read_lock(). Solution in mainline was to empty then nameidata
manually, drop out of RCU mode and then do put_path().
In effect, we open-code the things eventual terminate_walk()
would've done on error in RCU mode. That looks badly out of place
and confusing. We could add a comment along the lines of the
explanation above, but... there's a simpler solution. Call
unlazy_walk() even if legitimaze_path() fails. It will take
us out of RCU mode, so we'll be able to do path_put(link).
Yes, it will do unnecessary work - attempt to grab references
on the stuff in nameidata, only to have them dropped as soon
as we return the error to upper layer and get terminate_walk()
called there. So what? We are thoroughly off the fast path
by that point - we had GFP_ATOMIC allocation fail, we had
->d_seq or mount_lock mismatch and we are about to try walking
the same path from scratch in non-RCU mode. Which will need
to do the same allocation, this time with GFP_KERNEL, so it will
be able to apply memory pressure for blocking stuff.
Compared to that the cost of several lockref_get_not_dead()
is noise. And the logics become much easier to understand
that way.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
