There is currently no good way to query the page cache state of large file
sets and directory trees. There is mincore(), but it scales poorly: the
kernel writes out a lot of bitmap data that userspace has to aggregate,
when the user really doesn not care about per-page information in that
case. The user also needs to mmap and unmap each file as it goes along,
which can be quite slow as well.
Some use cases where this information could come in handy:
* Allowing database to decide whether to perform an index scan or
direct table queries based on the in-memory cache state of the
index.
* Visibility into the writeback algorithm, for performance issues
diagnostic.
* Workload-aware writeback pacing: estimating IO fulfilled by page
cache (and IO to be done) within a range of a file, allowing for
more frequent syncing when and where there is IO capacity, and
batching when there is not.
* Computing memory usage of large files/directory trees, analogous to
the du tool for disk usage.
More information about these use cases could be found in the following
thread:
https://lore.kernel.org/lkml/20230315170934.GA97793@cmpxchg.org/
This patch implements a new syscall that queries cache state of a file and
summarizes the number of cached pages, number of dirty pages, number of
pages marked for writeback, number of (recently) evicted pages, etc. in a
given range. Currently, the syscall is only wired in for x86
architecture.
NAME
cachestat - query the page cache statistics of a file.
SYNOPSIS
#include <sys/mman.h>
struct cachestat_range {
__u64 off;
__u64 len;
};
struct cachestat {
__u64 nr_cache;
__u64 nr_dirty;
__u64 nr_writeback;
__u64 nr_evicted;
__u64 nr_recently_evicted;
};
int cachestat(unsigned int fd, struct cachestat_range *cstat_range,
struct cachestat *cstat, unsigned int flags);
DESCRIPTION
cachestat() queries the number of cached pages, number of dirty
pages, number of pages marked for writeback, number of evicted
pages, number of recently evicted pages, in the bytes range given by
`off` and `len`.
An evicted page is a page that is previously in the page cache but
has been evicted since. A page is recently evicted if its last
eviction was recent enough that its reentry to the cache would
indicate that it is actively being used by the system, and that
there is memory pressure on the system.
These values are returned in a cachestat struct, whose address is
given by the `cstat` argument.
The `off` and `len` arguments must be non-negative integers. If
`len` > 0, the queried range is [`off`, `off` + `len`]. If `len` ==
0, we will query in the range from `off` to the end of the file.
The `flags` argument is unused for now, but is included for future
extensibility. User should pass 0 (i.e no flag specified).
Currently, hugetlbfs is not supported.
Because the status of a page can change after cachestat() checks it
but before it returns to the application, the returned values may
contain stale information.
RETURN VALUE
On success, cachestat returns 0. On error, -1 is returned, and errno
is set to indicate the error.
ERRORS
EFAULT cstat or cstat_args points to an invalid address.
EINVAL invalid flags.
EBADF invalid file descriptor.
EOPNOTSUPP file descriptor is of a hugetlbfs file
[nphamcs@gmail.com: replace rounddown logic with the existing helper]
Link: https://lkml.kernel.org/r/20230504022044.3675469-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20230503013608.2431726-3-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "cachestat: a new syscall for page cache state of files",
v13.
There is currently no good way to query the page cache statistics of large
files and directory trees. There is mincore(), but it scales poorly: the
kernel writes out a lot of bitmap data that userspace has to aggregate,
when the user really does not care about per-page information in that
case. The user also needs to mmap and unmap each file as it goes along,
which can be quite slow as well.
Some use cases where this information could come in handy:
* Allowing database to decide whether to perform an index scan or direct
table queries based on the in-memory cache state of the index.
* Visibility into the writeback algorithm, for performance issues
diagnostic.
* Workload-aware writeback pacing: estimating IO fulfilled by page cache
(and IO to be done) within a range of a file, allowing for more
frequent syncing when and where there is IO capacity, and batching
when there is not.
* Computing memory usage of large files/directory trees, analogous to
the du tool for disk usage.
More information about these use cases could be found in this thread:
https://lore.kernel.org/lkml/20230315170934.GA97793@cmpxchg.org/
This series of patches introduces a new system call, cachestat, that
summarizes the page cache statistics (number of cached pages, dirty pages,
pages marked for writeback, evicted pages etc.) of a file, in a specified
range of bytes. It also include a selftest suite that tests some typical
usage. Currently, the syscall is only wired in for x86 architecture.
This interface is inspired by past discussion and concerns with fincore,
which has a similar design (and as a result, issues) as mincore. Relevant
links:
https://lkml.indiana.edu/hypermail/linux/kernel/1302.1/04207.htmlhttps://lkml.indiana.edu/hypermail/linux/kernel/1302.1/04209.html
I have also developed a small tool that computes the memory usage of files
and directories, analogous to the du utility. User can choose between
mincore or cachestat (with cachestat exporting more information than
mincore). To compare the performance of these two options, I benchmarked
the tool on the root directory of a Meta's server machine, each for five
runs:
Using cachestat
real -- Median: 33.377s, Average: 33.475s, Standard Deviation: 0.3602
user -- Median: 4.08s, Average: 4.1078s, Standard Deviation: 0.0742
sys -- Median: 28.823s, Average: 28.8866s, Standard Deviation: 0.2689
Using mincore:
real -- Median: 102.352s, Average: 102.3442s, Standard Deviation: 0.2059
user -- Median: 10.149s, Average: 10.1482s, Standard Deviation: 0.0162
sys -- Median: 91.186s, Average: 91.2084s, Standard Deviation: 0.2046
I also ran both syscalls on a 2TB sparse file:
Using cachestat:
real 0m0.009s
user 0m0.000s
sys 0m0.009s
Using mincore:
real 0m37.510s
user 0m2.934s
sys 0m34.558s
Very large files like this are the pathological case for mincore. In
fact, to compute the stats for a single 2TB file, mincore takes as long as
cachestat takes to compute the stats for the entire tree! This could
easily happen inadvertently when we run it on subdirectories. Mincore is
clearly not suitable for a general-purpose command line tool.
Regarding security concerns, cachestat() should not pose any additional
issues. The caller already has read permission to the file itself (since
they need an fd to that file to call cachestat). This means that the
caller can access the underlying data in its entirety, which is a much
greater source of information (and as a result, a much greater security
risk) than the cache status itself.
The latest API change (in v13 of the patch series) is suggested by Jens
Axboe. It allows for 64-bit length argument, even on 32-bit architecture
(which is previously not possible due to the limit on the number of
syscall arguments). Furthermore, it eliminates the need for compatibility
handling - every user can use the same ABI.
This patch (of 4):
In preparation for computing recently evicted pages in cachestat, refactor
workingset_refault and lru_gen_refault to expose a helper function that
would test if an evicted page is recently evicted.
[penguin-kernel@I-love.SAKURA.ne.jp: add missing rcu_read_unlock() in lru_gen_refault()]
Link: https://lkml.kernel.org/r/610781bc-cf11-fc89-a46f-87cb8235d439@I-love.SAKURA.ne.jp
Link: https://lkml.kernel.org/r/20230503013608.2431726-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20230503013608.2431726-2-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Before commit 29ef680ae7 ("memcg, oom: move out_of_memory back to the
charge path"), all memcg oom killers were delayed to page fault path. And
the explicit wakeup is used in this case:
thread A:
...
if (locked) { // complete oom-kill, hold the lock
mem_cgroup_oom_unlock(memcg);
...
}
...
thread B:
...
if (locked && !memcg->oom_kill_disable) {
...
} else {
schedule(); // can't acquire the lock
...
}
...
The reason is that thread A kicks off the OOM-killer, which leads to
wakeups from the uncharges of the exiting task. But thread B is not
guaranteed to see them if it enters the OOM path after the OOM kills but
before thread A releases the lock.
Now only oom_kill_disable case is handled from the #PF path. In that case
it is userspace to trigger the wake up not the #PF path itself. All
potential paths to free some charges are responsible to call
memcg_oom_recover() , so the explicit wakeup is not needed in the
mem_cgroup_oom_synchronize() path which doesn't release any memory itself.
Link: https://lkml.kernel.org/r/20230419030739.115845-2-haifeng.xu@shopee.com
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "cgroup: eliminate atomic rstat flushing", v5.
A previous patch series [1] changed most atomic rstat flushing contexts to
become non-atomic. This was done to avoid an expensive operation that
scales with # cgroups and # cpus to happen with irqs disabled and
scheduling not permitted. There were two remaining atomic flushing
contexts after that series. This series tries to eliminate them as well,
eliminating atomic rstat flushing completely.
The two remaining atomic flushing contexts are:
(a) wb_over_bg_thresh()->mem_cgroup_wb_stats()
(b) mem_cgroup_threshold()->mem_cgroup_usage()
For (a), flushing needs to be atomic as wb_writeback() calls
wb_over_bg_thresh() with a spinlock held. However, it seems like the call
to wb_over_bg_thresh() doesn't need to be protected by that spinlock, so
this series proposes a refactoring that moves the call outside the lock
criticial section and makes the stats flushing in mem_cgroup_wb_stats()
non-atomic.
For (b), flushing needs to be atomic as mem_cgroup_threshold() is called
with irqs disabled. We only flush the stats when calculating the root
usage, as it is approximated as the sum of some memcg stats (file, anon,
and optionally swap) instead of the conventional page counter. This
series proposes changing this calculation to use the global stats instead,
eliminating the need for a memcg stat flush.
After these 2 contexts are eliminated, we no longer need
mem_cgroup_flush_stats_atomic() or cgroup_rstat_flush_atomic(). We can
remove them and simplify the code.
[1] https://lore.kernel.org/linux-mm/20230330191801.1967435-1-yosryahmed@google.com/
This patch (of 5):
wb_over_bg_thresh() calls mem_cgroup_wb_stats() which invokes an rstat
flush, which can be expensive on large systems. Currently,
wb_writeback() calls wb_over_bg_thresh() within a lock section, so we
have to do the rstat flush atomically. On systems with a lot of
cpus and/or cgroups, this can cause us to disable irqs for a long time,
potentially causing problems.
Move the call to wb_over_bg_thresh() outside the lock section in
preparation to make the rstat flush in mem_cgroup_wb_stats() non-atomic.
The list_empty(&wb->work_list) check should be okay outside the lock
section of wb->list_lock as it is protected by a separate lock
(wb->work_lock), and wb_over_bg_thresh() doesn't seem like it is
modifying any of wb->b_* lists the wb->list_lock is protecting.
Also, the loop seems to be already releasing and reacquring the
lock, so this refactoring looks safe.
Link: https://lkml.kernel.org/r/20230421174020.2994750-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20230421174020.2994750-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For the /proc/sys/vm/compact_memory file, the admin-guide states: When 1
is written to the file, all zones are compacted such that free memory is
available in contiguous blocks where possible. This can be important for
example in the allocation of huge pages although processes will also
directly compact memory as required
But it was not strictly followed, writing any value would cause all zones
to be compacted.
It has been slightly optimized to comply with the admin-guide. Enforce
the 1 on the unlikely chance that the sysctl handler is ever extended to
do something different.
Commit ef49843841 ("mm/compaction: remove unused variable
sysctl_compact_memory") has also been optimized a bit here, as the
declaration in the external header file has been eliminated, and
sysctl_compact_memory also needs to be verified.
[akpm@linux-foundation.org: add __read_mostly, per Mel]
Link: https://lkml.kernel.org/r/tencent_DFF54DB2A60F3333F97D3F6B5441519B050A@qq.com
Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: William Lam <william.lam@bytedance.com>
Cc: Pintu Kumar <pintu@codeaurora.org>
Cc: Fu Wei <wefu@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "memcg: OOM log improvements", v2.
This short patch series brings back some cgroup v1 stats in OOM logs
that were unnecessarily changed before. It also makes memcg OOM logs
less reliant on printk() internals.
This patch (of 2):
Commit c8713d0b23 ("mm: memcontrol: dump memory.stat during cgroup OOM")
made sure we dump all the stats in memory.stat during a cgroup OOM, but it
also introduced a slight behavioral change. The code used to print the
non-hierarchical v1 cgroup stats for the entire cgroup subtree, now it
only prints the v2 cgroup stats for the cgroup under OOM.
For cgroup v1 users, this introduces a few problems:
(a) The non-hierarchical stats of the memcg under OOM are no longer
shown.
(b) A couple of v1-only stats (e.g. pgpgin, pgpgout) are no longer
shown.
(c) We show the list of cgroup v2 stats, even in cgroup v1. This list
of stats is not tracked with v1 in mind. While most of the stats seem
to be working on v1, there may be some stats that are not fully or
correctly tracked.
Although OOM log is not set in stone, we should not change it for no
reason. When upgrading the kernel version to a version including commit
c8713d0b23 ("mm: memcontrol: dump memory.stat during cgroup OOM"), these
behavioral changes are noticed in cgroup v1.
The fix is simple. Commit c8713d0b23 ("mm: memcontrol: dump memory.stat
during cgroup OOM") separated stats formatting from stats display for v2,
to reuse the stats formatting in the OOM logs. Do the same for v1.
Move the v2 specific formatting from memory_stat_format() to
memcg_stat_format(), add memcg1_stat_format() for v1, and make
memory_stat_format() select between them based on cgroup version. Since
memory_stat_show() now works for both v1 & v2, drop memcg_stat_show().
Link: https://lkml.kernel.org/r/20230428132406.2540811-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20230428132406.2540811-3-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, we format all the memcg stats into a buffer in
mem_cgroup_print_oom_meminfo() and use pr_info() to dump it to the logs.
However, this buffer is large in size. Although it is currently working
as intended, ther is a dependency between the memcg stats buffer and the
printk record size limit.
If we add more stats in the future and the buffer becomes larger than the
printk record size limit, or if the prink record size limit is reduced,
the logs may be truncated.
It is safer to use seq_buf_do_printk(), which will automatically break up
the buffer at line breaks and issue small printk() calls.
Refactor the code to move the seq_buf from memory_stat_format() to its
callers, and use seq_buf_do_printk() to print the seq_buf in
mem_cgroup_print_oom_meminfo().
Link: https://lkml.kernel.org/r/20230428132406.2540811-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The MIGRATE_SYNC_LIGHT mode is intended to block for things that will
finish quickly but not for things that will take a long time. Exactly how
long is too long is not well defined, but waits of tens of milliseconds is
likely non-ideal.
When putting a Chromebook under memory pressure (opening over 90 tabs on a
4GB machine) it was fairly easy to see delays waiting for some locks in
the kcompactd code path of > 100 ms. While the laptop wasn't amazingly
usable in this state, it was still limping along and this state isn't
something artificial. Sometimes we simply end up with a lot of memory
pressure.
Putting the same Chromebook under memory pressure while it was running
Android apps (though not stressing them) showed a much worse result (NOTE:
this was on a older kernel but the codepaths here are similar). Android
apps on ChromeOS currently run from a 128K-block, zlib-compressed,
loopback-mounted squashfs disk. If we get a page fault from something
backed by the squashfs filesystem we could end up holding a folio lock
while reading enough from disk to decompress 128K (and then decompressing
it using the somewhat slow zlib algorithms). That reading goes through
the ext4 subsystem (because it's a loopback mount) before eventually
ending up in the block subsystem. This extra jaunt adds extra overhead.
Without much work I could see cases where we ended up blocked on a folio
lock for over a second. With more extreme memory pressure I could see up
to 25 seconds.
We considered adding a timeout in the case of MIGRATE_SYNC_LIGHT for the
two locks that were seen to be slow [1] and that generated much
discussion. After discussion, it was decided that we should avoid waiting
for the two locks during MIGRATE_SYNC_LIGHT if they were being held for
IO. We'll continue with the unbounded wait for the more full SYNC modes.
With this change, I couldn't see any slow waits on these locks with my
previous testcases.
NOTE: The reason I stated digging into this originally isn't because some
benchmark had gone awry, but because we've received in-the-field crash
reports where we have a hung task waiting on the page lock (which is the
equivalent code path on old kernels). While the root cause of those
crashes is likely unrelated and won't be fixed by this patch, analyzing
those crash reports did point out these very long waits seemed like
something good to fix. With this patch we should no longer hang waiting
on these locks, but presumably the system will still be in a bad shape and
hang somewhere else.
[1] https://lore.kernel.org/r/20230421151135.v2.1.I2b71e11264c5c214bc59744b9e13e4c353bc5714@changeid
Link: https://lkml.kernel.org/r/20230428135414.v3.1.Ia86ccac02a303154a0b8bc60567e7a95d34c96d3@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
A memcg pointer in the percpu stock can be accessed by drain_all_stock()
from another cpu in a lockless way. In theory it might lead to an issue,
similar to the one which has been discovered with stock->cached_objcg,
where the pointer was zeroed between the check for being NULL and
dereferencing. In this case the issue is unlikely a real problem, but to
make it bulletproof and similar to stock->cached_objcg, let's annotate all
accesses to stock->cached with READ_ONCE()/WTRITE_ONCE().
Link: https://lkml.kernel.org/r/20230502160839.361544-2-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeelb@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull x86 cpu fix from Thomas Gleixner:
"A single fix for x86:
- Prevent a bogus setting for the number of HT siblings, which is
caused by the CPUID evaluation trainwreck of X86. That recomputes
the value for each CPU, so the last CPU "wins". That can cause
completely bogus sibling values"
* tag 'x86-urgent-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/topology: Fix erroneous smp_num_siblings on Intel Hybrid platforms
Pull perf fixes from Thomas Gleixner:
"A small set of perf fixes:
- Make the MSR-readout based CHA discovery work around broken
discovery tables in some SPR firmwares.
- Prevent saving PEBS configuration which has software bits set that
cause a crash when restored into the relevant MSR"
* tag 'perf-urgent-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/uncore: Correct the number of CHAs on SPR
perf/x86/intel: Save/restore cpuc->active_pebs_data_cfg when using guest PEBS
Pull unwinder fixes from Thomas Gleixner:
"A set of unwinder and tooling fixes:
- Ensure that the stack pointer on x86 is aligned again so that the
unwinder does not read past the end of the stack
- Discard .note.gnu.property section which has a pointlessly
different alignment than the other note sections. That confuses
tooling of all sorts including readelf, libbpf and pahole"
* tag 'objtool-urgent-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/show_trace_log_lvl: Ensure stack pointer is aligned, again
vmlinux.lds.h: Discard .note.gnu.property section
Pull debugobjects fixes from Thomas Gleixner:
"Two fixes for debugobjects:
- Prevent the allocation path from waking up kswapd.
That's a long standing issue due to the GFP_ATOMIC allocation flag.
As debug objects can be invoked from pretty much any context waking
kswapd can end up in arbitrary lock chains versus the waitqueue
lock
- Correct the explicit lockdep wait-type violation in
debug_object_fill_pool()"
* tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
debugobjects: Don't wake up kswapd from fill_pool()
debugobjects,locking: Annotate debug_object_fill_pool() wait type violation
Pull irq fixes from Thomas Gleixner:
"A set of fixes for interrupt chip drivers:
- Prevent loss of state in the MIPS GIC interrupt controller
- Disable pseudo NMIs on Mediatek based Chromebooks as they have
firmware issues which cause instantenous chrashes and freezes wen
pseudo NMIs are used
- Fix the error handling path in the MBIGEN driver and a defined but
not used warning in the meson-gpio interrupt chip driver"
* tag 'irq-urgent-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqchip/mbigen: Unify the error handling in mbigen_of_create_domain()
irqchip/meson-gpio: Mark OF related data as maybe unused
irqchip/mips-gic: Use raw spinlock for gic_lock
irqchip/mips-gic: Don't touch vl_map if a local interrupt is not routable
irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware issues
dt-bindings: interrupt-controller: arm,gic-v3: Add quirk for Mediatek SoCs w/ broken FW
Pull MIPS fixes from Thomas Bogendoerfer:
- fixes to get alchemy platform back in shape
- fix for initrd detection
* tag 'mips-fixes_6.4_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
mips: Move initrd_start check after initrd address sanitisation.
MIPS: Alchemy: fix dbdma2
MIPS: Restore Au1300 support
MIPS: unhide PATA_PLATFORM
Pull powerpc fix from Michael Ellerman:
- Reinstate ARCH_FORCE_MAX_ORDER ranges to fix various breakage
* tag 'powerpc-6.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/mm: Reinstate ARCH_FORCE_MAX_ORDER ranges
Pull xen fixes from Juergen Gross:
- a double free fix in the Xen pvcalls backend driver
- a fix for a regression causing the MSI related sysfs entries to not
being created in Xen PV guests
- a fix in the Xen blkfront driver for handling insane input data
better
* tag 'for-linus-6.4-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
x86/pci/xen: populate MSI sysfs entries
xen/pvcalls-back: fix double frees with pvcalls_new_active_socket()
xen/blkfront: Only check REQ_FUA for writes
Pull char/misc fixes from Greg KH:
"Here are some small driver fixes for 6.4-rc4. They are just two
different types:
- binder fixes and reverts for reported problems and regressions in
the binder "driver".
- coresight driver fixes for reported problems.
All of these have been in linux-next for over a week with no reported
problems"
* tag 'char-misc-6.4-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
binder: fix UAF of alloc->vma in race with munmap()
binder: add lockless binder_alloc_(set|get)_vma()
Revert "android: binder: stop saving a pointer to the VMA"
Revert "binder_alloc: add missing mmap_lock calls when using the VMA"
binder: fix UAF caused by faulty buffer cleanup
coresight: perf: Release Coresight path when alloc trace id failed
coresight: Fix signedness bug in tmc_etr_buf_insert_barrier_packet()
Pull compute express link fixes from Dan Williams:
"The 'media ready' series prevents the driver from acting on bad
capacity information, and it moves some checks earlier in the init
sequence which impacts topics in the queue for 6.5.
Additional hotplug testing uncovered a missing enable for memory
decode. A debug crash fix is also included.
Summary:
- Stop trusting capacity data before the "media ready" indication
- Add missing HDM decoder capability enable for the cold-plug case
- Fix a debug message induced crash"
* tag 'cxl-fixes-6.4-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl:
cxl: Explicitly initialize resources when media is not ready
cxl/port: Fix NULL pointer access in devm_cxl_add_port()
cxl: Move cxl_await_media_ready() to before capacity info retrieval
cxl: Wait Memory_Info_Valid before access memory related info
cxl/port: Enable the HDM decoder capability for switch ports
Pull ARM SoC fixes from Arnd Bergmann:
"There have not been a lot of fixes for for the soc tree in 6.4, but
these have been sitting here for too long.
For the devicetree side, there is one minor warning fix for vexpress,
the rest all all for the the NXP i.MX platforms: SoC specific bugfixes
for the iMX8 clocks and its USB-3.0 gadget device, as well as board
specific fixes for regulators and the phy on some of the i.MX boards.
The microchip risc-v and arm32 maintainers now also add a shared
maintainer file entry for the arm64 parts.
The remaining fixes are all for firmware drivers, addressing mistakes
in the optee, scmi and ff-a firmware driver implementation, mostly in
the error handling code, incorrect use of the alloc_workqueue()
interface in SCMI, and compatibility with corner cases of the firmware
implementation"
* tag 'arm-fixes-6.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc:
MAINTAINERS: update arm64 Microchip entries
arm64: dts: imx8: fix USB 3.0 Gadget Failure in QM & QXPB0 at super speed
dt-binding: cdns,usb3: Fix cdns,on-chip-buff-size type
arm64: dts: colibri-imx8x: delete adc1 and dsp
arm64: dts: colibri-imx8x: fix iris pinctrl configuration
arm64: dts: colibri-imx8x: move pinctrl property from SoM to eval board
arm64: dts: colibri-imx8x: fix eval board pin configuration
arm64: dts: imx8mp: Fix video clock parents
ARM: dts: imx6qdl-mba6: Add missing pvcie-supply regulator
ARM: dts: imx6ull-dhcor: Set and limit the mode for PMIC buck 1, 2 and 3
arm64: dts: imx8mn-var-som: fix PHY detection bug by adding deassert delay
arm64: dts: imx8mn: Fix video clock parents
firmware: arm_ffa: Set reserved/MBZ fields to zero in the memory descriptors
firmware: arm_ffa: Fix FFA device names for logical partitions
firmware: arm_ffa: Fix usage of partition info get count flag
firmware: arm_ffa: Check if ffa_driver remove is present before executing
arm64: dts: arm: add missing cache properties
ARM: dts: vexpress: add missing cache properties
firmware: arm_scmi: Fix incorrect alloc_workqueue() invocation
optee: fix uninited async notif value
Pull PCI fix from Bjorn Helgaas:
- Quirk Ice Lake Root Ports to work around DPC log size issue (Mika
Westerberg)
* tag 'pci-v6.4-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci:
PCI/DPC: Quirk PIO log size for Intel Ice Lake Root Ports
Pull VFIO fix from Alex Williamson:
- Test for and return error for invalid pfns through the pin pages
interface (Yan Zhao)
* tag 'vfio-v6.4-rc4' of https://github.com/awilliam/linux-vfio:
vfio/type1: check pfn valid before converting to struct page
Pull block fixes from Jens Axboe:
"A few fixes for the storage side of things:
- Fix bio caching condition for passthrough IO (Anuj)
- end-of-device check fix for zero sized devices (Christoph)
- Update Paolo's email address
- NVMe pull request via Keith with a single quirk addition
- Fix regression in how wbt enablement is done (Yu)
- Fix race in active queue accounting (Tian)"
* tag 'block-6.4-2023-05-26' of git://git.kernel.dk/linux:
NVMe: Add MAXIO 1602 to bogus nid list.
block: make bio_check_eod work for zero sized devices
block: fix bio-cache for passthru IO
block, bfq: update Paolo's address in maintainer list
blk-mq: fix race condition in active queue accounting
blk-wbt: fix that wbt can't be disabled by default
Pull io_uring fix from Jens Axboe:
"Just a single fix for the conditional schedule with the SQPOLL thread,
dropping the uring_lock if we do need to reschedule"
* tag 'io_uring-6.4-2023-05-26' of git://git.kernel.dk/linux:
io_uring: unlock sqd->lock before sq thread release CPU
Pull thermal control fix from Rafael Wysocki:
"Fix a regression introduced inadvertently during the 6.3 cycle by a
commit making the Intel int340x thermal driver use sysfs_emit_at()
instead of scnprintf() (Srinivas Pandruvada)"
* tag 'thermal-6.4-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
thermal: intel: int340x: Add new line for UUID display
Pull power management fixes from Rafael Wysocki:
"Fix three issues related to the ->fast_switch callback in the AMD
P-state cpufreq driver (Gautham R. Shenoy and Wyes Karny)"
* tag 'pm-6.4-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpufreq: amd-pstate: Update policy->cur in amd_pstate_adjust_perf()
cpufreq: amd-pstate: Remove fast_switch_possible flag from active driver
cpufreq: amd-pstate: Add ->fast_switch() callback
When media is not ready do not assume that the capacity information from
the identify command is valid, i.e. ->total_bytes
->partition_align_bytes ->{volatile,persistent}_only_bytes. Explicitly
zero out the capacity resources and exit early.
Given zero-init of those fields this patch is functionally equivalent to
the prior state, but it improves readability and robustness going
forward.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168506118166.3004974.13523455340007852589.stgit@djiang5-mobl3
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Pull gpio fixes from Bartosz Golaszewski:
- fix incorrect output in in-tree gpio tools
- fix a shell coding issue in gpio-sim selftests
- correctly set the permissions for debugfs attributes exposed by
gpio-mockup
- fix chip name and pin count in gpio-f7188x for one of the supported
models
- fix numberspace pollution when using dynamically and statically
allocated GPIOs together
* tag 'gpio-fixes-for-v6.4-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
gpio-f7188x: fix chip name and pin count on Nuvoton chip
gpiolib: fix allocation of mixed dynamic/static GPIOs
gpio: mockup: Fix mode of debugfs files
selftests: gpio: gpio-sim: Fix BUG: test FAILED due to recent change
tools: gpio: fix debounce_period_us output of lsgpio
Pull btrfs fixes from David Sterba:
- handle memory allocation error in checksumming helper (reported by
syzbot)
- fix lockdep splat when aborting a transaction, add NOFS protection
around invalidate_inode_pages2 that could allocate with GFP_KERNEL
- reduce chances to hit an ENOSPC during scrub with RAID56 profiles
* tag 'for-6.4-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: use nofs when cleaning up aborted transactions
btrfs: handle memory allocation failure in btrfs_csum_one_bio
btrfs: scrub: try harder to mark RAID56 block groups read-only
Pull drm fixes from Dave Airlie:
"This week's collection is pretty spread out, accel/qaic has a bunch of
fixes, amdgpu, then lots of single fixes across a bunch of places.
core:
- fix drmm_mutex_init lock class
mgag200:
- fix gamma lut initialisation
pl111:
- fix FB depth on IMPD-1 framebuffer
amdgpu:
- Fix missing BO unlocking in KIQ error path
- Avoid spurious secure display error messages
- SMU13 fix
- Fix an OD regression
- GPU reset display IRQ warning fix
- MST fix
radeon:
- Fix a DP regression
i915:
- PIPEDMC disabling fix for bigjoiner config
panel:
- fix aya neo air plus quirk
sched:
- remove redundant NULL check
qaic:
- fix NNC message corruption
- Grab ch_lock during QAIC_ATTACH_SLICE_BO
- Flush the transfer list again
- Validate if BO is sliced before slicing
- Validate user data before grabbing any lock
- initialize ret variable to 0
- silence some uninitialized variable warnings"
* tag 'drm-fixes-2023-05-26' of git://anongit.freedesktop.org/drm/drm:
drm/amd/display: Have Payload Properly Created After Resume
drm/amd/display: Fix warning in disabling vblank irq
drm/amd/pm: Fix output of pp_od_clk_voltage
drm/amd/pm: add missing NotifyPowerSource message mapping for SMU13.0.7
drm/radeon: reintroduce radeon_dp_work_func content
drm/amdgpu: don't enable secure display on incompatible platforms
drm:amd:amdgpu: Fix missing buffer object unlock in failure path
accel/qaic: Fix NNC message corruption
accel/qaic: Grab ch_lock during QAIC_ATTACH_SLICE_BO
accel/qaic: Flush the transfer list again
accel/qaic: Validate if BO is sliced before slicing
accel/qaic: Validate user data before grabbing any lock
accel/qaic: initialize ret variable to 0
drm/i915: Fix PIPEDMC disabling for a bigjoiner configuration
drm: fix drmm_mutex_init()
drm/sched: Remove redundant check
drm: panel-orientation-quirks: Change Air's quirk to support Air Plus
accel/qaic: silence some uninitialized variable warnings
drm/pl111: Fix FB depth on IMPD-1 framebuffer
drm/mgag200: Fix gamma lut not initialized.
I tried to streamline our user memory copy code fairly aggressively in
commit adfcf4231b ("x86: don't use REP_GOOD or ERMS for user memory
copies"), in order to then be able to clean up the code and inline the
modern FSRM case in commit 577e6a7fd5 ("x86: inline the 'rep movs' in
user copies for the FSRM case").
We had reports [1] of that causing regressions earlier with blogbench,
but that turned out to be a horrible benchmark for that case, and not a
sufficient reason for re-instating "rep movsb" on older machines.
However, now Eric Dumazet reported [2] a regression in performance that
seems to be a rather more real benchmark, where due to the removal of
"rep movs" a TCP stream over a 100Gbps network no longer reaches line
speed.
And it turns out that with the simplified the calling convention for the
non-FSRM case in commit 427fda2c8a ("x86: improve on the non-rep
'copy_user' function"), re-introducing the ERMS case is actually fairly
simple.
Of course, that "fairly simple" is glossing over several missteps due to
having to fight our assembler alternative code. This code really wanted
to rewrite a conditional branch to have two different targets, but that
made objtool sufficiently unhappy that this instead just ended up doing
a choice between "jump to the unrolled loop, or use 'rep movsb'
directly".
Let's see if somebody finds a case where the kernel memory copies also
care (see commit 68674f94ff: "x86: don't use REP_GOOD or ERMS for
small memory copies"). But Eric does argue that the user copies are
special because networking tries to copy up to 32KB at a time, if
order-3 pages allocations are possible.
In-kernel memory copies are typically small, unless they are the special
"copy pages at a time" kind that still use "rep movs".
Link: https://lore.kernel.org/lkml/202305041446.71d46724-yujie.liu@intel.com/ [1]
Link: https://lore.kernel.org/lkml/CANn89iKUbyrJ=r2+_kK+sb2ZSSHifFZ7QkPLDpAtkJ8v4WUumA@mail.gmail.com/ [2]
Reported-and-tested-by: Eric Dumazet <edumazet@google.com>
Fixes: adfcf4231b ("x86: don't use REP_GOOD or ERMS for user memory copies")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull NVMe fix from Keith:
"nvme fixes for 6.4
One nvme quirk (Tatsuki)"
* tag 'nvme-6.4-2023-05-26' of git://git.infradead.org/nvme:
NVMe: Add MAXIO 1602 to bogus nid list.
Arm FF-A fixes for v6.4
Quite a few fixes to address set of assorted issues:
1. NULL pointer dereference if the ffa driver doesn't provide remove()
callback as it is currently executed unconditionally
2. FF-A core probe failure on systems with v1.0 firmware as the new
partition info get count flag is used unconditionally
3. Failure to register more than one logical partition or service within
the same physical partition as the device name contains only VM ID
which will be same for all but each will have unique UUID.
4. Rejection of certain memory interface transmissions by the receivers
(secure partitions) as few MBZ fields are non-zero due to lack of
explicit re-initialization of those fields
* tag 'ffa-fixes-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
firmware: arm_ffa: Set reserved/MBZ fields to zero in the memory descriptors
firmware: arm_ffa: Fix FFA device names for logical partitions
firmware: arm_ffa: Fix usage of partition info get count flag
firmware: arm_ffa: Check if ffa_driver remove is present before executing
Link: https://lore.kernel.org/r/20230509143453.1188753-1-sudeep.holla@arm.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Pull smb directory moves and client fixes from Steve French:
"Four smb3 client fixes (three of which marked for stable) and three
patches to move of fs/cifs and fs/ksmbd to a new common "fs/smb"
parent directory
- Move the client and server source directories to a common parent
directory:
fs/cifs -> fs/smb/client
fs/ksmbd -> fs/smb/server
fs/smbfs_common -> fs/smb/common
- important readahead fix
- important fix for SMB1 regression
- fix for missing mount option ("mapchars") in mount API conversion
- minor debugging improvement"
* tag '6.4-rc3-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
smb3: move Documentation/filesystems/cifs to Documentation/filesystems/smb
cifs: correct references in Documentation to old fs/cifs path
smb: move client and server files to common directory fs/smb
cifs: mapchars mount option ignored
smb3: display debug information better for encryption
cifs: fix smb1 mount regression
cifs: Fix cifs_limit_bvec_subset() to correctly check the maxmimum size
Pull parisc architecture fixes from Helge Deller:
"Quite a bunch of real bugfixes in here and most of them are tagged for
backporting: A fix for cache flushing from irq context, a kprobes &
kgdb breakpoint handling fix, and a fix in the alternative code
patching function to take care of CPU hotplugging.
parisc now provides LOCKDEP support and comes with a lightweight
spinlock check. Both features helped me to find the cache flush bug.
Additionally writing the AGP gatt has been fixed, the machine allows
the user to reboot after a system halt and arch_sync_dma_for_cpu() has
been optimized for PCXL PCUs.
Summary:
- Fix flush_dcache_page() for usage from irq context
- Handle kprobes breakpoints only in kernel context
- Handle kgdb breakpoints only in kernel context
- Use num_present_cpus() in alternative patching code
- Enable LOCKDEP support
- Add lightweight spinlock checks
- Flush AGP gatt writes and adjust gatt mask in parisc_agp_mask_memory()
- Allow to reboot machine after system halt
- Improve cache flushing for PCXL in arch_sync_dma_for_cpu()"
* tag 'parisc-for-6.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Fix flush_dcache_page() for usage from irq context
parisc: Handle kgdb breakpoints only in kernel context
parisc: Handle kprobes breakpoints only in kernel context
parisc: Allow to reboot machine after system halt
parisc: Enable LOCKDEP support
parisc: Add lightweight spinlock checks
parisc: Use num_present_cpus() in alternative patching code
parisc: Flush gatt writes and adjust gatt mask in parisc_agp_mask_memory()
parisc: Improve cache flushing for PCXL in arch_sync_dma_for_cpu()
It turns out that udev under certain circumstances will concurrently try
to load the same modules over-and-over excessively. This isn't a kernel
bug, but it ends up affecting the kernel, to the point that under
certain circumstances we can fail to boot, because the kernel uses a lot
of memory to read all the module data all at once.
Note that it isn't a memory leak, it's just basically a thundering herd
problem happening at bootup with a lot of CPUs, with the worst cases
then being pretty bad.
Admittedly the worst situations are somewhat contrived: lots and lots of
CPUs, not a lot of memory, and KASAN enabled to make it all slower and
as such (unintentionally) exacerbate the problem.
Luis explains: [1]
"My best assessment of the situation is that each CPU in udev ends up
triggering a load of duplicate set of modules, not just one, but *a
lot*. Not sure what heuristics udev uses to load a set of modules per
CPU."
Petr Pavlu chimes in: [2]
"My understanding is that udev workers are forked. An initial kmod
context is created by the main udevd process but no sharing happens
after the fork. It means that the mentioned memory pool logic doesn't
really kick in.
Multiple parallel load requests come from multiple udev workers, for
instance, each handling an udev event for one CPU device and making
the exactly same requests as all others are doing at the same time.
The optimization idea would be to recognize these duplicate requests
at the udevd/kmod level and converge them"
Note that module loading has tried to mitigate this issue before, see
for example commit 064f4536d1 ("module: avoid allocation if module is
already present and ready"), which has a few ASCII graphs on memory use
due to this same issue.
However, while that noticed that the module was already loaded, and
exited with an error early before spending any more time on setting up
the module, it didn't handle the case of multiple concurrent module
loads all being active - but not complete - at the same time.
Yes, one of them will eventually win the race and finalize its copy, and
the others will then notice that the module already exists and error
out, but while this all happens, we have tons of unnecessary concurrent
work being done.
Again, the real fix is for udev to not do that (maybe it should use
threads instead of fork, and have actual shared data structures and not
cause duplicate work). That real fix is apparently not trivial.
But it turns out that the kernel already has a pretty good model for
dealing with concurrent access to the same file: the i_writecount of the
inode.
In fact, the module loading already indirectly uses 'i_writecount' ,
because 'kernel_file_read()' will in fact do
ret = deny_write_access(file);
if (ret)
return ret;
...
allow_write_access(file);
around the read of the file data. We do not allow concurrent writes to
the file, and return -ETXTBUSY if the file was open for writing at the
same time as the module data is loaded from it.
And the solution to the reader concurrency problem is to simply extend
this "no concurrent writers" logic to simply be "exclusive access".
Note that "exclusive" in this context isn't really some absolute thing:
it's only exclusion from writers and from other "special readers" that
do this writer denial. So we simply introduce a variation of that
"deny_write_access()" logic that not only denies write access, but also
requires that this is the _only_ such access that denies write access.
Which means that you can't start loading a module that is already being
loaded as a module by somebody else, or you will get the same -ETXTBSY
error that you would get if there were writers around.
[ It also means that you can't try to load a currently executing
executable as a module, for the same reason: executables do that same
"deny_write_access()" thing, and that's obviously where the whole
ETXTBSY logic traditionally came from.
This is not a problem for kernel modules, since the set of normal
executable files and kernel module files is entirely disjoint. ]
This new function is called "exclusive_deny_write_access()", and the
implementation is trivial, in that it's just an atomic decrement of
i_writecount if it was 0 before.
To use that new exclusivity check, all we then do is wrap the module
loading with that exclusive_deny_write_access()() / allow_write_access()
pair. The actual patch is a bit bigger than that, because we want to
surround not just the "load file data" part, but the whole module setup,
to get maximum exclusion.
So this ends up splitting up "finit_module()" into a few helper
functions to make it all very clear and legible.
In Luis' test-case (bringing up 255 vcpu's in a virtual machine [3]),
the "wasted vmalloc" space (ie module data read into a vmalloc'ed area
in order to be loaded as a module, but then discarded because somebody
else loaded the same module instead) dropped from 1.8GiB to 474kB. Yes,
that's gigabytes to kilobytes.
It doesn't drop completely to zero, because even with this change, you
can still end up having completely serial pointless module loads, where
one udev process has loaded a module fully (and thus the kernel has
released that exclusive lock on the module file), and then another udev
process tries to load the same module again.
So while we cannot fully get rid of the fundamental bug in user space,
we _can_ get rid of the excessive concurrent thundering herd effect.
A couple of final side notes on this all:
- This tweak only affects the "finit_module()" system call, which gives
the kernel a file descriptor with the module data.
You can also just feed the module data as raw data from user space
with "init_module()" (note the lack of 'f' at the beginning), and
obviously for that case we do _not_ have any "exclusive read" logic.
So if you absolutely want to do things wrong in user space, and try
to load the same module multiple times, and error out only later when
the kernel ends up saying "you can't load the same module name
twice", you can still do that.
And in fact, some distros will do exactly that, because they will
uncompress the kernel module data in user space before feeding it to
the kernel (mainly because they haven't started using the new kernel
side decompression yet).
So this is not some absolute "you can't do concurrent loads of the
same module". It's literally just a very simple heuristic that will
catch it early in case you try to load the exact same module file at
the same time, and in that case avoid a potentially nasty situation.
- There is another user of "deny_write_access()": the verity code that
enables fs-verity on a file (the FS_IOC_ENABLE_VERITY ioctl).
If you use fs-verity and you care about verifying the kernel modules
(which does make sense), you should do it *before* loading said
kernel module. That may sound obvious, but now the implementation
basically requires it. Because if you try to do it concurrently, the
kernel may refuse to load the module file that is being set up by the
fs-verity code.
- This all will obviously mean that if you insist on loading the same
module in parallel, only one module load will succeed, and the others
will return with an error.
That was true before too, but what is different is that the -ETXTBSY
error can be returned *before* the success case of another process
fully loading and instantiating the module.
Again, that might sound obvious, and it is indeed the whole point of
the whole change: we are much quicker to notice the whole "you're
already in the process of loading this module".
So it's very much intentional, but it does mean that if you just
spray the kernel with "finit_module()", and expect that the module is
immediately loaded afterwards without checking the return value, you
are doing something horribly horribly wrong.
I'd like to say that that would never happen, but the whole _reason_
for this commit is that udev is currently doing something horribly
horribly wrong, so ...
Link: https://lore.kernel.org/all/ZEGopJ8VAYnE7LQ2@bombadil.infradead.org/ [1]
Link: https://lore.kernel.org/all/23bd0ce6-ef78-1cd8-1f21-0e706a00424a@suse.com/ [2]
Link: https://lore.kernel.org/lkml/ZG%2Fa+nrt4%2FAAUi5z@bombadil.infradead.org/ [3]
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Petr Pavlu <petr.pavlu@suse.com>
Tested-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs fixes from Christian Brauner:
- During the acl rework we merged this cycle the generic_listxattr()
helper had to be modified in a way that in principle it would allow
for POSIX ACLs to be reported. At least that was the impression we
had initially. Because before the acl rework POSIX ACLs would be
reported if the filesystem did have POSIX ACL xattr handlers in
sb->s_xattr. That logic changed and now we can simply check whether
the superblock has SB_POSIXACL set and if the inode has
inode->i_{default_}acl set report the appropriate POSIX ACL name.
However, we didn't realize that generic_listxattr() was only ever
used by two filesystems. Both of them don't support POSIX ACLs via
sb->s_xattr handlers and so never reported POSIX ACLs via
generic_listxattr() even if they raised SB_POSIXACL and did contain
inodes which had acls set. The example here is nfs4.
As a result, generic_listxattr() suddenly started reporting POSIX
ACLs when it wouldn't have before. Since SB_POSIXACL implies that the
umask isn't stripped in the VFS nfs4 can't just drop SB_POSIXACL from
the superblock as it would also alter umask handling for them.
So just have generic_listxattr() not report POSIX ACLs as it never
did anyway. It's documented as such.
- Our SB_* flags currently use a signed integer and we shift the last
bit causing UBSAN to complain about undefined behavior. Switch to
using unsigned. While the original patch used an explicit unsigned
bitshift it's now pretty common to rely on the BIT() macro in a lot
of headers nowadays. So the patch has been adjusted to use that.
- Add Namjae as ntfs reviewer. They're already active this cycle so
let's make it explicit right now.
* tag 'vfs/v6.4-rc3/misc.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
ntfs: Add myself as a reviewer
fs: don't call posix_acl_listxattr in generic_listxattr
fs: fix undefined behavior in bit shift for SB_NOUSER
