While checking the results of the :c:func: removal, I noticed that there
was no documentation for request_irq(), and request_threaded_irq() was not
mentioned at all. Add a kerneldoc comment for request_irq() and add
request_threaded_irq() to the list of functions.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The second paragraph of the content section does not properly
describe how mount points are determined by autofs.
Replace the lines detailing how the determination of these mount
points is "ad hoc" by a short description of the mount map syntax
used by autofs.
Signed-off-by: Jaskaran Singh <jaskaransingh7654321@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Some of the struct definitions now have an autofs packet header.
Reflect these changes by adding a definition of this header and
place it wherever suitable.
Signed-off-by: Jaskaran Singh <jaskaransingh7654321@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Convert autofs.txt to reST.
The following changes abound:
- Introduce reST formatting for headings, lists et al.
- Add an indentation of an 8 space tab wherever suitable, so as
to maintain consistency.
- Remove indentation of the description of the ioctls which are similar
to the AUTOFS_IOC ioctls, as it does not come out quite right in HTML.
- Add an entry for autofs in the index.
Signed-off-by: Jaskaran Singh <jaskaransingh7654321@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Instead of requesting the "ext" clock and handling the watchdog clock
divider and gating in the watchdog driver, we now request and use the
"wdt" clock that is supplied by the ingenic-timer "TCU" driver.
The major benefit is that the watchdog's clock rate and parent can now
be specified from within devicetree, instead of hardcoded in the driver.
Also, this driver won't poke anymore into the TCU registers to
enable/disable the clock, as this is now handled by the TCU driver.
On the bad side, we break the ABI with devicetree - as we now request a
different clock. In this very specific case it is still okay, as every
Ingenic JZ47xx-based board out there compile the devicetree within the
kernel; so it's still time to push breaking changes, in order to get a
clean devicetree that won't break once it musn't.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191023174714.14362-1-paul@crapouillou.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Testing with the new fsstress support for subvolumes uncovered a pretty
bad problem with rename exchange on subvolumes. We're modifying two
different subvolumes, but we only start the transaction on one of them,
so the other one is not added to the dirty root list. This is caught by
btrfs_cow_block() with a warning because the root has not been updated,
however if we do not modify this root again we'll end up pointing at an
invalid root because the root item is never updated.
Fix this by making sure we add the destination root to the trans list,
the same as we do with normal renames. This fixes the corruption.
Fixes: cdd1fedf82 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The ast2600 no longer uses bit 4 in the control register to indicate a
1MHz clock (It now controls whether this watchdog is reset by a SOC
reset). This means we do not want to set it. It also does not need to be
set for the ast2500, as it is read-only on that SoC.
The comment next to the clock rate selection wandered away from where it
was set, so put it back next to the register setting it's describing.
Fixes: b3528b4874 ("watchdog: aspeed: Add support for AST2600")
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191108032905.22463-1-joel@jms.id.au
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
The following hang is observed when a 'reboot' command is issued:
# reboot
# Stopping network: OK
Stopping klogd: OK
Stopping syslogd: OK
umount: devtmpfs busy - remounted read-only
[ 8.612079] EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system reboot
[ 10.694753] reboot: Restarting system
[ 11.699008] Reboot failed -- System halted
Fix this problem by adding a .restart ops member.
Fixes: 41b630f41b ("watchdog: Add i.MX7ULP watchdog support")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191029174037.25381-1-festevam@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
It can be useful to delay setting the nowayout feature for a watchdog
device. Moreover, not every driver (notably gpio_wdt) implements a
nowayout module parameter/otherwise respects CONFIG_WATCHDOG_NOWAYOUT,
and modifying those drivers carries a risk of causing a regression for
someone who has two watchdog devices, sets CONFIG_WATCHDOG_NOWAYOUT
and somehow relies on the gpio_wdt driver being ignorant of
that (i.e., allowing one to gracefully close a gpio_wdt but not the
other watchdog in the system).
So instead, simply make the nowayout sysfs file writable. Obviously,
setting nowayout is a one-way street.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191105205118.11359-1-linux@rasmusvillemoes.dk
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
When PREEMPT_RT is enabled, all hrtimer expiry functions are
deferred for execution into the context of ksoftirqd unless otherwise
annotated.
Deferring the expiry of the hrtimer used by the watchdog core, however,
is a waste, as the callback does nothing but queue a kthread work item
and wakeup watchdogd.
It's worst then that, too: the deferral through ksoftirqd also means
that for correct behavior a user must adjust the scheduling parameters
of both watchdogd _and_ ksoftirqd, which is unnecessary and has other
side effects (like causing unrelated expiry functions to execute at
potentially elevated priority).
Instead, mark the hrtimer used by the watchdog core as being _HARD to
allow it's execution directly from hardirq context. The work done in
this expiry function is well-bounded and minimal.
A user still must adjust the scheduling parameters of the watchdogd
to be correct w.r.t. their application needs.
Link: https://lkml.kernel.org/r/0e02d8327aeca344096c246713033887bc490dd7.1538089180.git.julia@ni.com
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Reported-by: Tim Sander <tim@krieglstein.org>
Signed-off-by: Julia Cartwright <julia@ni.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
[bigeasy: use only HRTIMER_MODE_REL_HARD]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191105144506.clyadjbvnn7b7b2m@linutronix.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
The struct cdev is embedded in the struct watchdog_core_data. In the
current code, we manage the watchdog_core_data with a kref, but the
cdev is manged by a kobject. There is no any relationship between
this kref and kobject. So it is possible that the watchdog_core_data is
freed before the cdev is entirely released. We can easily get the
following call trace with CONFIG_DEBUG_KOBJECT_RELEASE and
CONFIG_DEBUG_OBJECTS_TIMERS enabled.
ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x38
WARNING: CPU: 23 PID: 1028 at lib/debugobjects.c:481 debug_print_object+0xb0/0xf0
Modules linked in: softdog(-) deflate ctr twofish_generic twofish_common camellia_generic serpent_generic blowfish_generic blowfish_common cast5_generic cast_common cmac xcbc af_key sch_fq_codel openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
CPU: 23 PID: 1028 Comm: modprobe Not tainted 5.3.0-next-20190924-yoctodev-standard+ #180
Hardware name: Marvell OcteonTX CN96XX board (DT)
pstate: 00400009 (nzcv daif +PAN -UAO)
pc : debug_print_object+0xb0/0xf0
lr : debug_print_object+0xb0/0xf0
sp : ffff80001cbcfc70
x29: ffff80001cbcfc70 x28: ffff800010ea2128
x27: ffff800010bad000 x26: 0000000000000000
x25: ffff80001103c640 x24: ffff80001107b268
x23: ffff800010bad9e8 x22: ffff800010ea2128
x21: ffff000bc2c62af8 x20: ffff80001103c600
x19: ffff800010e867d8 x18: 0000000000000060
x17: 0000000000000000 x16: 0000000000000000
x15: ffff000bd7240470 x14: 6e6968207473696c
x13: 5f72656d6974203a x12: 6570797420746365
x11: 6a626f2029302065 x10: 7461747320657669
x9 : 7463612820657669 x8 : 3378302f3078302b
x7 : 0000000000001d7a x6 : ffff800010fd5889
x5 : 0000000000000000 x4 : 0000000000000000
x3 : 0000000000000000 x2 : ffff000bff948548
x1 : 276a1c9e1edc2300 x0 : 0000000000000000
Call trace:
debug_print_object+0xb0/0xf0
debug_check_no_obj_freed+0x1e8/0x210
kfree+0x1b8/0x368
watchdog_cdev_unregister+0x88/0xc8
watchdog_dev_unregister+0x38/0x48
watchdog_unregister_device+0xa8/0x100
softdog_exit+0x18/0xfec4 [softdog]
__arm64_sys_delete_module+0x174/0x200
el0_svc_handler+0xd0/0x1c8
el0_svc+0x8/0xc
This is a common issue when using cdev embedded in a struct.
Fortunately, we already have a mechanism to solve this kind of issue.
Please see commit 233ed09d7f ("chardev: add helper function to
register char devs with a struct device") for more detail.
In this patch, we choose to embed the struct device into the
watchdog_core_data, and use the API provided by the commit 233ed09d7f
to make sure that the release of watchdog_core_data and cdev are
in sequence.
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191008112934.29669-1-haokexin@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Any arm config which has 'CONFIG_MTD_ONENAND_SAMSUNG=m' and
'CONFIG_SERIAL_SAMSUNG=m' gives a build warning:
warning: same module names found:
drivers/tty/serial/samsung.ko
drivers/mtd/nand/onenand/samsung.ko
Rename both drivers/tty/serial/samsung.c to
drivers/tty/serial/samsung_tty.c and drivers/mtd/nand/onenand/samsung.c
drivers/mtd/nand/onenand/samsung_mtd.c to fix the warning.
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Acked-by: Richard Weinberger <richard@nod.at>
Link: https://lore.kernel.org/r/20191117202435.28127-1-sudipm.mukherjee@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
set_page_dirty says:
For pages with a mapping this should be done under the page lock
for the benefit of asynchronous memory errors who prefer a
consistent dirty state. This rule can be broken in some special
cases, but should be better not to.
Under those rules, it is only safe for us to use the plain set_page_dirty
calls for shmemfs/anonymous memory. Userptr may be used with real
mappings and so needs to use the locked version (set_page_dirty_lock).
However, following a try_to_unmap() we may want to remove the userptr and
so call put_pages(). However, try_to_unmap() acquires the page lock and
so we must avoid recursively locking the pages ourselves -- which means
that we cannot safely acquire the lock around set_page_dirty(). Since we
can't be sure of the lock, we have to risk skip dirtying the page, or
else risk calling set_page_dirty() without a lock and so risk fs
corruption.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203317
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112012
Fixes: 5cc9ed4b9a ("drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl")
References: cb6d7c7dc7 ("drm/i915/userptr: Acquire the page lock around set_page_dirty()")
References: 505a8ec7e1 ("Revert "drm/i915/userptr: Acquire the page lock around set_page_dirty()"")
References: 6dcc693bc5 ("ext4: warn when page is dirtied without buffers")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191111133205.11590-1-chris@chris-wilson.co.uk
(cherry picked from commit 0d4bbe3d40)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
(cherry picked from commit cee7fb437e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
The LUTs are single buffered so in order to program them without
tearing we'd have to do it during vblank (actually to be 100%
effective it has to happen between start of vblank and frame start).
We have no proper mechanism for that at the moment so we just
defer loading them after the vblank waits have happened. That
is not quite sufficient (especially when committing multiple pipes
whose vblanks don't line up) so the LUT load will often leak into
the following frame causing tearing.
However in case the hardware wasn't previously using the LUT we
can preload it before setting the enable bit (which is double
buffered so won't tear). Let's determine if we can do such
preloading and make it happen. Slight variation between the
hardware requires some platforms specifics in the checks.
Hans is seeing ugly colored flash on VLV/CHV macchines (GPD win
and Asus T100HA) when the gamma LUT gets loaded for the first
time as the BIOS has left some junk in the LUT memory.
v2: Deal with uapi vs. hw crtc state split
s/GCM/CGM/ typo fix
Cc: Hans de Goede <hdegoede@redhat.com>
Fixes: 051a6d8d3c ("drm/i915: Move LUT programming to happen after vblank waits")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191030190815.7359-1-ville.syrjala@linux.intel.com
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
(cherry picked from commit 0ccc42a2fd)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
(cherry picked from commit f77021372e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
When doing a device replace, while at scrub.c:scrub_enumerate_chunks(), we
set the block group to RO mode and then wait for any ongoing writes into
extents of the block group to complete. While doing that wait we overwrite
the value of the variable 'ret' and can break out of the loop if an error
happens without turning the block group back into RW mode. So what happens
is the following:
1) btrfs_inc_block_group_ro() returns 0, meaning it set the block group
to RO mode (its ->ro field set to 1 or incremented to some value > 1);
2) Then btrfs_wait_ordered_roots() returns a value > 0;
3) Then if either joining or committing the transaction fails, we break
out of the loop wihtout calling btrfs_dec_block_group_ro(), leaving
the block group in RO mode forever.
To fix this, just remove the code that waits for ongoing writes to extents
of the block group, since it's not needed because in the initial setup
phase of a device replace operation, before starting to find all chunks
and their extents, we set the target device for replace while holding
fs_info->dev_replace->rwsem, which ensures that after releasing that
semaphore, any writes into the source device are made to the target device
as well (__btrfs_map_block() guarantees that). So while at
scrub_enumerate_chunks() we only need to worry about finding and copying
extents (from the source device to the target device) that were written
before we started the device replace operation.
Fixes: f0e9b7d640 ("Btrfs: fix race setting block group readonly during device replace")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
When running btrfs/072 with only one online CPU, it has a pretty high
chance to fail:
btrfs/072 12s ... _check_dmesg: something found in dmesg (see xfstests-dev/results//btrfs/072.dmesg)
- output mismatch (see xfstests-dev/results//btrfs/072.out.bad)
--- tests/btrfs/072.out 2019-10-22 15:18:14.008965340 +0800
+++ /xfstests-dev/results//btrfs/072.out.bad 2019-11-14 15:56:45.877152240 +0800
@@ -1,2 +1,3 @@
QA output created by 072
Silence is golden
+Scrub find errors in "-m dup -d single" test
...
And with the following call trace:
BTRFS info (device dm-5): scrub: started on devid 1
------------[ cut here ]------------
BTRFS: Transaction aborted (error -27)
WARNING: CPU: 0 PID: 55087 at fs/btrfs/block-group.c:1890 btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs]
CPU: 0 PID: 55087 Comm: btrfs Tainted: G W O 5.4.0-rc1-custom+ #13
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs]
Call Trace:
__btrfs_end_transaction+0xdb/0x310 [btrfs]
btrfs_end_transaction+0x10/0x20 [btrfs]
btrfs_inc_block_group_ro+0x1c9/0x210 [btrfs]
scrub_enumerate_chunks+0x264/0x940 [btrfs]
btrfs_scrub_dev+0x45c/0x8f0 [btrfs]
btrfs_ioctl+0x31a1/0x3fb0 [btrfs]
do_vfs_ioctl+0x636/0xaa0
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x43/0x50
do_syscall_64+0x79/0xe0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
---[ end trace 166c865cec7688e7 ]---
[CAUSE]
The error number -27 is -EFBIG, returned from the following call chain:
btrfs_end_transaction()
|- __btrfs_end_transaction()
|- btrfs_create_pending_block_groups()
|- btrfs_finish_chunk_alloc()
|- btrfs_add_system_chunk()
This happens because we have used up all space of
btrfs_super_block::sys_chunk_array.
The root cause is, we have the following bad loop of creating tons of
system chunks:
1. The only SYSTEM chunk is being scrubbed
It's very common to have only one SYSTEM chunk.
2. New SYSTEM bg will be allocated
As btrfs_inc_block_group_ro() will check if we have enough space
after marking current bg RO. If not, then allocate a new chunk.
3. New SYSTEM bg is still empty, will be reclaimed
During the reclaim, we will mark it RO again.
4. That newly allocated empty SYSTEM bg get scrubbed
We go back to step 2, as the bg is already mark RO but still not
cleaned up yet.
If the cleaner kthread doesn't get executed fast enough (e.g. only one
CPU), then we will get more and more empty SYSTEM chunks, using up all
the space of btrfs_super_block::sys_chunk_array.
[FIX]
Since scrub/dev-replace doesn't always need to allocate new extent,
especially chunk tree extent, so we don't really need to do chunk
pre-allocation.
To break above spiral, here we introduce a new parameter to
btrfs_inc_block_group(), @do_chunk_alloc, which indicates whether we
need extra chunk pre-allocation.
For relocation, we pass @do_chunk_alloc=true, while for scrub, we pass
@do_chunk_alloc=false.
This should keep unnecessary empty chunks from popping up for scrub.
Also, since there are two parameters for btrfs_inc_block_group_ro(),
add more comment for it.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
struct btrfs_fs_devices::rotating currently is declared as an integer
variable but only used as a boolean.
Change the variable definition to bool and update to code touching it to
set 'true' and 'false'.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
struct btrfs_fs_devices::seeding currently is declared as an integer
variable but only used as a boolean.
Change the variable definition to bool and update to code touching it to
set 'true' and 'false'.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The type name is misleading, a single entry is named 'cache' while this
normally means a collection of objects. Rename that everywhere. Also the
identifier was quite long, making function prototypes harder to format.
Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For read_one_block_group(), its only caller has already got the item key
to search next block group item.
So we can use that key directly without doing our own convertion on
stack.
Also, since that key used in btrfs_read_block_groups() is vital for
block group item search, add 'const' keyword for that parameter to
prevent read_one_block_group() to modify it.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Refactor the work inside the loop of btrfs_read_block_groups() into one
separate function, read_one_block_group().
This allows read_one_block_group to be reused for later BG_TREE feature.
The refactor does the following extra fix:
- Use btrfs_fs_incompat() to replace open-coded feature check
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
A nice writeup of the LKMM (Linux Kernel Memory Model) rules for access
once policies can be found here
https://lwn.net/Articles/799218/#Access-Marking%20Policies .
The locked and unlocked access to eb::blocking_writers should be
annotated accordingly, following this:
Writes:
- locked write must use ONCE, may use plain read
- unlocked write must use ONCE
Reads:
- unlocked read must use ONCE
- locked read may use plain read iff not mixed with unlocked read
- unlocked read then locked must use ONCE
There's one difference on the assembly level, where
btrfs_tree_read_lock_atomic and btrfs_try_tree_read_lock used the cached
value and did not reevaluate it after taking the lock. This could have
missed some opportunities to take the lock in case blocking writers
changed between the calls, but the window is just a few instructions
long. As this is in try-lock, the callers handle that.
Signed-off-by: David Sterba <dsterba@suse.com>
The increment and decrement was inherited from previous version that
used atomics, switched in commit 06297d8cef ("btrfs: switch
extent_buffer blocking_writers from atomic to int"). The only possible
values are 0 and 1 so we can set them directly.
The generated assembly (gcc 9.x) did the direct value assignment in
btrfs_set_lock_blocking_write (asm diff after change in 06297d8cef):
5d: test %eax,%eax
5f: je 62 <btrfs_set_lock_blocking_write+0x22>
61: retq
- 62: lock incl 0x44(%rdi)
- 66: add $0x50,%rdi
- 6a: jmpq 6f <btrfs_set_lock_blocking_write+0x2f>
+ 62: movl $0x1,0x44(%rdi)
+ 69: add $0x50,%rdi
+ 6d: jmpq 72 <btrfs_set_lock_blocking_write+0x32>
The part in btrfs_tree_unlock did a decrement because
BUG_ON(blockers > 1) is probably not a strong hint for the compiler, but
otherwise the output looks safe:
- lock decl 0x44(%rdi)
+ sub $0x1,%eax
+ mov %eax,0x44(%rdi)
Signed-off-by: David Sterba <dsterba@suse.com>
There are two ifs that use eb::blocking_writers. As this is a variable
modified inside and outside of locks, we could minimize number of
accesses to avoid problems with getting different results at different
times.
The access here is locked so this can only race with btrfs_tree_unlock
that sets blocking_writers to 0 without lock and unsets the lock owner.
The first branch is taken only if the same thread already holds the
lock, the second if checks for blocking writers. Here we'd either unlock
and wait, or proceed. Both are valid states of the locking protocol.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
When there are no raid1c3 or raid1c4 block groups left after balance
(either convert or with other filters applied), remove the incompat bit.
This is already done for RAID56, do the same for RAID1C34.
Signed-off-by: David Sterba <dsterba@suse.com>
