Pull vfs d_revalidate updates from Al Viro:
"Provide stable parent and name to ->d_revalidate() instances
Most of the filesystem methods where we care about dentry name and
parent have their stability guaranteed by the callers;
->d_revalidate() is the major exception.
It's easy enough for callers to supply stable values for expected name
and expected parent of the dentry being validated. That kills quite a
bit of boilerplate in ->d_revalidate() instances, along with a bunch
of races where they used to access ->d_name without sufficient
precautions"
* tag 'pull-revalidate' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
9p: fix ->rename_sem exclusion
orangefs_d_revalidate(): use stable parent inode and name passed by caller
ocfs2_dentry_revalidate(): use stable parent inode and name passed by caller
nfs: fix ->d_revalidate() UAF on ->d_name accesses
nfs{,4}_lookup_validate(): use stable parent inode passed by caller
gfs2_drevalidate(): use stable parent inode and name passed by caller
fuse_dentry_revalidate(): use stable parent inode and name passed by caller
vfat_revalidate{,_ci}(): use stable parent inode passed by caller
exfat_d_revalidate(): use stable parent inode passed by caller
fscrypt_d_revalidate(): use stable parent inode passed by caller
ceph_d_revalidate(): propagate stable name down into request encoding
ceph_d_revalidate(): use stable parent inode passed by caller
afs_d_revalidate(): use stable name and parent inode passed by caller
Pass parent directory inode and expected name to ->d_revalidate()
generic_ci_d_compare(): use shortname_storage
ext4 fast_commit: make use of name_snapshot primitives
dissolve external_name.u into separate members
make take_dentry_name_snapshot() lockless
dcache: back inline names with a struct-wrapped array of unsigned long
make sure that DNAME_INLINE_LEN is a multiple of word size
->d_revalidate() often needs to access dentry parent and name; that has
to be done carefully, since the locking environment varies from caller
to caller. We are not guaranteed that dentry in question will not be
moved right under us - not unless the filesystem is such that nothing
on it ever gets renamed.
It can be dealt with, but that results in boilerplate code that isn't
even needed - the callers normally have just found the dentry via dcache
lookup and want to verify that it's in the right place; they already
have the values of ->d_parent and ->d_name stable. There is a couple
of exceptions (overlayfs and, to less extent, ecryptfs), but for the
majority of calls that song and dance is not needed at all.
It's easier to make ecryptfs and overlayfs find and pass those values if
there's a ->d_revalidate() instance to be called, rather than doing that
in the instances.
This commit only changes the calling conventions; making use of supplied
values is left to followups.
NOTE: some instances need more than just the parent - things like CIFS
may need to build an entire path from filesystem root, so they need
more precautions than the usual boilerplate. This series doesn't
do anything to that need - these filesystems have to keep their locking
mechanisms (rename_lock loops, use of dentry_path_raw(), private rwsem
a-la v9fs).
One thing to keep in mind when using name is that name->name will normally
point into the pathname being resolved; the filename in question occupies
name->len bytes starting at name->name, and there is NUL somewhere after it,
but it the next byte might very well be '/' rather than '\0'. Do not
ignore name->len.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Gabriel Krisman Bertazi <gabriel@krisman.be>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull virtio updates from Michael Tsirkin:
"A small number of improvements all over the place:
- vdpa/octeon support for multiple interrupts
- virtio-pci support for error recovery
- vp_vdpa support for notification with data
- vhost/net fix to set num_buffers for spec compliance
- virtio-mem now works with kdump on s390
And small cleanups all over the place"
* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (23 commits)
virtio_blk: Add support for transport error recovery
virtio_pci: Add support for PCIe Function Level Reset
vhost/net: Set num_buffers for virtio 1.0
vdpa/octeon_ep: read vendor-specific PCI capability
virtio-pci: define type and header for PCI vendor data
vdpa/octeon_ep: handle device config change events
vdpa/octeon_ep: enable support for multiple interrupts per device
vdpa: solidrun: Replace deprecated PCI functions
s390/kdump: virtio-mem kdump support (CONFIG_PROC_VMCORE_DEVICE_RAM)
virtio-mem: support CONFIG_PROC_VMCORE_DEVICE_RAM
virtio-mem: remember usable region size
virtio-mem: mark device ready before registering callbacks in kdump mode
fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM ranges in 2nd kernel
fs/proc/vmcore: factor out freeing a list of vmcore ranges
fs/proc/vmcore: factor out allocating a vmcore range and adding it to a list
fs/proc/vmcore: move vmcore definitions out of kcore.h
fs/proc/vmcore: prefix all pr_* with "vmcore:"
fs/proc/vmcore: disallow vmcore modifications while the vmcore is open
fs/proc/vmcore: replace vmcoredd_mutex by vmcore_mutex
fs/proc/vmcore: convert vmcore_cb_lock into vmcore_mutex
...
Let's implement the get_device_ram() vmcore callback, so
architectures that select NEED_PROC_VMCORE_NEED_DEVICE_RAM, like s390
soon, can include that memory in a crash dump.
Merge ranges, and process ranges that might contain a mixture of plugged
and unplugged, to reduce the total number of ranges.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-12-david@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
s390 allocates+prepares the elfcore hdr in the dump (2nd) kernel, not in
the crashed kernel.
RAM provided by memory devices such as virtio-mem can only be detected
using the device driver; when vmcore_init() is called, these device
drivers are usually not loaded yet, or the devices did not get probed
yet. Consequently, on s390 these RAM ranges will not be included in
the crash dump, which makes the dump partially corrupt and is
unfortunate.
Instead of deferring the vmcore_init() call, to an (unclear?) later point,
let's reuse the vmcore_cb infrastructure to obtain device RAM ranges as
the device drivers probe the device and get access to this information.
Then, we'll add these ranges to the vmcore, adding more PT_LOAD
entries and updating the offsets+vmcore size.
Use a separate Kconfig option to be set by an architecture to include this
code only if the arch really needs it. Further, we'll make the config
depend on the relevant drivers (i.e., virtio_mem) once they implement
support (next). The alternative of having a PROVIDE_PROC_VMCORE_DEVICE_RAM
config option was dropped for now for simplicity.
The current target use case is s390, which only creates an elf64
elfcore, so focusing on elf64 is sufficient.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-9-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
These vmcore defines are not related to /proc/kcore, move them out.
We'll move "struct vmcoredd_node" to vmcore.c, because it is only used
internally. While "struct vmcore" is only used internally for now,
we're planning on using it from inline functions in crash_dump.h next,
so move it to crash_dump.h.
While at it, rename "struct vmcore" to "struct vmcore_range", which is a
more suitable name and will make the usage of it outside of vmcore.c
clearer.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-6-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The vmcoredd_update_size() call and its effects (size/offset changes) are
currently completely unsynchronized, and will cause trouble when
performed concurrently, or when done while someone is already reading the
vmcore.
Let's protect all vmcore modifications by the vmcore_mutex, disallow vmcore
modifications while the vmcore is open, and warn on vmcore
modifications after the vmcore was already opened once: modifications
while the vmcore is open are unsafe, and modifications after the vmcore
was opened indicates trouble. Properly synchronize against concurrent
opening of the vmcore.
No need to grab the mutex during mmap()/read(): after we opened the
vmcore, modifications are impossible.
It's worth noting that modifications after the vmcore was opened are
completely unexpected, so failing if open, and warning if already opened
(+closed again) is good enough.
This change not only handles concurrent adding of device dumps +
concurrent reading of the vmcore properly, it also prepares for other
mechanisms that will modify the vmcore.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-4-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Now that we have a mutex that synchronizes against opening of the vmcore,
let's use that one to replace vmcoredd_mutex: there is no need to have
two separate ones.
This is a preparation for properly preventing vmcore modifications
after the vmcore was opened.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-3-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
We want to protect vmcore modifications from concurrent opening of
the vmcore, and also serialize vmcore modification.
(a) We can currently modify the vmcore after it was opened. This can happen
if a vmcoredd is added after the vmcore module was initialized and
already opened by user space. We want to fix that and prepare for
new code wanting to serialize against concurrent opening.
(b) To handle it cleanly we need to protect the modifications against
concurrent opening. As the modifications end up allocating memory and
can sleep, we cannot rely on the spinlock.
Let's convert the spinlock into a mutex to prepare for further changes.
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-2-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Pull MM updates from Andrew Morton:
"The various patchsets are summarized below. Plus of course many
indivudual patches which are described in their changelogs.
- "Allocate and free frozen pages" from Matthew Wilcox reorganizes
the page allocator so we end up with the ability to allocate and
free zero-refcount pages. So that callers (ie, slab) can avoid a
refcount inc & dec
- "Support large folios for tmpfs" from Baolin Wang teaches tmpfs to
use large folios other than PMD-sized ones
- "Fix mm/rodata_test" from Petr Tesarik performs some maintenance
and fixes for this small built-in kernel selftest
- "mas_anode_descend() related cleanup" from Wei Yang tidies up part
of the mapletree code
- "mm: fix format issues and param types" from Keren Sun implements a
few minor code cleanups
- "simplify split calculation" from Wei Yang provides a few fixes and
a test for the mapletree code
- "mm/vma: make more mmap logic userland testable" from Lorenzo
Stoakes continues the work of moving vma-related code into the
(relatively) new mm/vma.c
- "mm/page_alloc: gfp flags cleanups for alloc_contig_*()" from David
Hildenbrand cleans up and rationalizes handling of gfp flags in the
page allocator
- "readahead: Reintroduce fix for improper RA window sizing" from Jan
Kara is a second attempt at fixing a readahead window sizing issue.
It should reduce the amount of unnecessary reading
- "synchronously scan and reclaim empty user PTE pages" from Qi Zheng
addresses an issue where "huge" amounts of pte pagetables are
accumulated:
https://lore.kernel.org/lkml/cover.1718267194.git.zhengqi.arch@bytedance.com/
Qi's series addresses this windup by synchronously freeing PTE
memory within the context of madvise(MADV_DONTNEED)
- "selftest/mm: Remove warnings found by adding compiler flags" from
Muhammad Usama Anjum fixes some build warnings in the selftests
code when optional compiler warnings are enabled
- "mm: don't use __GFP_HARDWALL when migrating remote pages" from
David Hildenbrand tightens the allocator's observance of
__GFP_HARDWALL
- "pkeys kselftests improvements" from Kevin Brodsky implements
various fixes and cleanups in the MM selftests code, mainly
pertaining to the pkeys tests
- "mm/damon: add sample modules" from SeongJae Park enhances DAMON to
estimate application working set size
- "memcg/hugetlb: Rework memcg hugetlb charging" from Joshua Hahn
provides some cleanups to memcg's hugetlb charging logic
- "mm/swap_cgroup: remove global swap cgroup lock" from Kairui Song
removes the global swap cgroup lock. A speedup of 10% for a
tmpfs-based kernel build was demonstrated
- "zram: split page type read/write handling" from Sergey Senozhatsky
has several fixes and cleaups for zram in the area of
zram_write_page(). A watchdog softlockup warning was eliminated
- "move pagetable_*_dtor() to __tlb_remove_table()" from Kevin
Brodsky cleans up the pagetable destructor implementations. A rare
use-after-free race is fixed
- "mm/debug: introduce and use VM_WARN_ON_VMG()" from Lorenzo Stoakes
simplifies and cleans up the debugging code in the VMA merging
logic
- "Account page tables at all levels" from Kevin Brodsky cleans up
and regularizes the pagetable ctor/dtor handling. This results in
improvements in accounting accuracy
- "mm/damon: replace most damon_callback usages in sysfs with new
core functions" from SeongJae Park cleans up and generalizes
DAMON's sysfs file interface logic
- "mm/damon: enable page level properties based monitoring" from
SeongJae Park increases the amount of information which is
presented in response to DAMOS actions
- "mm/damon: remove DAMON debugfs interface" from SeongJae Park
removes DAMON's long-deprecated debugfs interfaces. Thus the
migration to sysfs is completed
- "mm/hugetlb: Refactor hugetlb allocation resv accounting" from
Peter Xu cleans up and generalizes the hugetlb reservation
accounting
- "mm: alloc_pages_bulk: small API refactor" from Luiz Capitulino
removes a never-used feature of the alloc_pages_bulk() interface
- "mm/damon: extend DAMOS filters for inclusion" from SeongJae Park
extends DAMOS filters to support not only exclusion (rejecting),
but also inclusion (allowing) behavior
- "Add zpdesc memory descriptor for zswap.zpool" from Alex Shi
introduces a new memory descriptor for zswap.zpool that currently
overlaps with struct page for now. This is part of the effort to
reduce the size of struct page and to enable dynamic allocation of
memory descriptors
- "mm, swap: rework of swap allocator locks" from Kairui Song redoes
and simplifies the swap allocator locking. A speedup of 400% was
demonstrated for one workload. As was a 35% reduction for kernel
build time with swap-on-zram
- "mm: update mips to use do_mmap(), make mmap_region() internal"
from Lorenzo Stoakes reworks MIPS's use of mmap_region() so that
mmap_region() can be made MM-internal
- "mm/mglru: performance optimizations" from Yu Zhao fixes a few
MGLRU regressions and otherwise improves MGLRU performance
- "Docs/mm/damon: add tuning guide and misc updates" from SeongJae
Park updates DAMON documentation
- "Cleanup for memfd_create()" from Isaac Manjarres does that thing
- "mm: hugetlb+THP folio and migration cleanups" from David
Hildenbrand provides various cleanups in the areas of hugetlb
folios, THP folios and migration
- "Uncached buffered IO" from Jens Axboe implements the new
RWF_DONTCACHE flag which provides synchronous dropbehind for
pagecache reading and writing. To permite userspace to address
issues with massive buildup of useless pagecache when
reading/writing fast devices
- "selftests/mm: virtual_address_range: Reduce memory" from Thomas
Weißschuh fixes and optimizes some of the MM selftests"
* tag 'mm-stable-2025-01-26-14-59' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
mm/compaction: fix UBSAN shift-out-of-bounds warning
s390/mm: add missing ctor/dtor on page table upgrade
kasan: sw_tags: use str_on_off() helper in kasan_init_sw_tags()
tools: add VM_WARN_ON_VMG definition
mm/damon/core: use str_high_low() helper in damos_wmark_wait_us()
seqlock: add missing parameter documentation for raw_seqcount_try_begin()
mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
mm/page_alloc: remove the incorrect and misleading comment
zram: remove zcomp_stream_put() from write_incompressible_page()
mm: separate move/undo parts from migrate_pages_batch()
mm/kfence: use str_write_read() helper in get_access_type()
selftests/mm/mkdirty: fix memory leak in test_uffdio_copy()
kasan: hw_tags: Use str_on_off() helper in kasan_init_hw_tags()
selftests/mm: virtual_address_range: avoid reading from VM_IO mappings
selftests/mm: vm_util: split up /proc/self/smaps parsing
selftests/mm: virtual_address_range: unmap chunks after validation
selftests/mm: virtual_address_range: mmap() without PROT_WRITE
selftests/memfd/memfd_test: fix possible NULL pointer dereference
mm: add FGP_DONTCACHE folio creation flag
mm: call filemap_fdatawrite_range_kick() after IOCB_DONTCACHE issue
...
In /proc/<pid>/ksm_stat, add two extra ksm involvement items including
KSM_mergeable and KSM_merge_any. It helps administrators to better know
the system's KSM behavior at process level.
ksm_merge_any: yes/no
whether the process'mm is added by prctl() into the candidate list
of KSM or not, and fully enabled at process level.
ksm_mergeable: yes/no
whether any VMAs of the process'mm are currently applicable to KSM.
Purpose
=======
These two items are just to improve the observability of KSM at process
level, so that users can know if a certain process has enabled KSM.
For example, if without these two items, when we look at
/proc/<pid>/ksm_stat and there's no merging pages found, We are not sure
whether it is because KSM was not enabled or because KSM did not
successfully merge any pages.
Although "mg" in /proc/<pid>/smaps indicate VM_MERGEABLE, it's opaque
and not very obvious for non professionals.
[akpm@linux-foundation.org: wording tweaks, per David and akpm]
Link: https://lkml.kernel.org/r/20250110174034304QOb8eDoqtFkp3_t8mqnqc@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull misc vfs updates from Christian Brauner:
"Features:
- Support caching symlink lengths in inodes
The size is stored in a new union utilizing the same space as
i_devices, thus avoiding growing the struct or taking up any more
space
When utilized it dodges strlen() in vfs_readlink(), giving about
1.5% speed up when issuing readlink on /initrd.img on ext4
- Add RWF_DONTCACHE iocb and FOP_DONTCACHE file_operations flag
If a file system supports uncached buffered IO, it may set
FOP_DONTCACHE and enable support for RWF_DONTCACHE.
If RWF_DONTCACHE is attempted without the file system supporting
it, it'll get errored with -EOPNOTSUPP
- Enable VBOXGUEST and VBOXSF_FS on ARM64
Now that VirtualBox is able to run as a host on arm64 (e.g. the
Apple M3 processors) we can enable VBOXSF_FS (and in turn
VBOXGUEST) for this architecture.
Tested with various runs of bonnie++ and dbench on an Apple MacBook
Pro with the latest Virtualbox 7.1.4 r165100 installed
Cleanups:
- Delay sysctl_nr_open check in expand_files()
- Use kernel-doc includes in fiemap docbook
- Use page->private instead of page->index in watch_queue
- Use a consume fence in mnt_idmap() as it's heavily used in
link_path_walk()
- Replace magic number 7 with ARRAY_SIZE() in fc_log
- Sort out a stale comment about races between fd alloc and dup2()
- Fix return type of do_mount() from long to int
- Various cosmetic cleanups for the lockref code
Fixes:
- Annotate spinning as unlikely() in __read_seqcount_begin
The annotation already used to be there, but got lost in commit
52ac39e5db ("seqlock: seqcount_t: Implement all read APIs as
statement expressions")
- Fix proc_handler for sysctl_nr_open
- Flush delayed work in delayed fput()
- Fix grammar and spelling in propagate_umount()
- Fix ESP not readable during coredump
In /proc/PID/stat, there is the kstkesp field which is the stack
pointer of a thread. While the thread is active, this field reads
zero. But during a coredump, it should have a valid value
However, at the moment, kstkesp is zero even during coredump
- Don't wake up the writer if the pipe is still full
- Fix unbalanced user_access_end() in select code"
* tag 'vfs-6.14-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (28 commits)
gfs2: use lockref_init for qd_lockref
erofs: use lockref_init for pcl->lockref
dcache: use lockref_init for d_lockref
lockref: add a lockref_init helper
lockref: drop superfluous externs
lockref: use bool for false/true returns
lockref: improve the lockref_get_not_zero description
lockref: remove lockref_put_not_zero
fs: Fix return type of do_mount() from long to int
select: Fix unbalanced user_access_end()
vbox: Enable VBOXGUEST and VBOXSF_FS on ARM64
pipe_read: don't wake up the writer if the pipe is still full
selftests: coredump: Add stackdump test
fs/proc: do_task_stat: Fix ESP not readable during coredump
fs: add RWF_DONTCACHE iocb and FOP_DONTCACHE file_operations flag
fs: sort out a stale comment about races between fd alloc and dup2
fs: Fix grammar and spelling in propagate_umount()
fs: fc_log replace magic number 7 with ARRAY_SIZE()
fs: use a consume fence in mnt_idmap()
file: flush delayed work in delayed fput()
...
Pull /proc/kcore updates from Christian Brauner:
"The performance of /proc/kcore reads has been showing up as a
bottleneck for the drgn debugger. drgn scripts often spend ~25% of
their time in the kernel reading from /proc/kcore.
A lot of this overhead comes from silly inefficiencies. This pull
request contains fixes for the low-hanging fruit. The fixes are all
fairly small and straightforward.
The result is a 25% improvement in read latency in micro-benchmarks
(from ~235 nanoseconds to ~175) and a 15% improvement in execution
time for real-world drgn scripts:
- Make /proc/kcore entry permanent
- Avoid walking the list on every read
- Use percpu_rw_semaphore for kclist_lock
- Make Omar Sandoval the official maintainer for /proc/kcore"
* tag 'vfs-6.14-rc1.kcore' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
MAINTAINERS: add me as /proc/kcore maintainer
proc/kcore: use percpu_rw_semaphore for kclist_lock
proc/kcore: don't walk list on every read
proc/kcore: mark proc entry as permanent
Since commit 5cbcb62ddd ("fs/proc: fix softlockup in __read_vmcore") the
number of softlockups in __read_vmcore at kdump time have gone down, but
they still happen sometimes.
In a memory constrained environment like the kdump image, a softlockup is
not just a harmless message, but it can interfere with things like RCU
freeing memory, causing the crashdump to get stuck.
The second loop in __read_vmcore has a lot more opportunities for natural
sleep points, like scheduling out while waiting for a data write to
happen, but apparently that is not always enough.
Add a cond_resched() to the second loop in __read_vmcore to (hopefully)
get rid of the softlockups.
Link: https://lkml.kernel.org/r/20250110102821.2a37581b@fangorn
Fixes: 5cbcb62ddd ("fs/proc: fix softlockup in __read_vmcore")
Signed-off-by: Rik van Riel <riel@surriel.com>
Reported-by: Breno Leitao <leitao@debian.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The field "eip" (instruction pointer) and "esp" (stack pointer) of a task
can be read from /proc/PID/stat. These fields can be interesting for
coredump.
However, these fields were disabled by commit 0a1eb2d474 ("fs/proc: Stop
reporting eip and esp in /proc/PID/stat"), because it is generally unsafe
to do so. But it is safe for a coredumping process, and therefore
exceptions were made:
- for a coredumping thread by commit fd7d56270b ("fs/proc: Report
eip/esp in /prod/PID/stat for coredumping").
- for all other threads in a coredumping process by commit cb8f381f16
("fs/proc/array.c: allow reporting eip/esp for all coredumping
threads").
The above two commits check the PF_DUMPCORE flag to determine a coredump thread
and the PF_EXITING flag for the other threads.
Unfortunately, commit 9230738308 ("coredump: Don't perform any cleanups
before dumping core") moved coredump to happen earlier and before PF_EXITING is
set. Thus, checking PF_EXITING is no longer the correct way to determine
threads in a coredumping process.
Instead of PF_EXITING, use PF_POSTCOREDUMP to determine the other threads.
Checking of PF_EXITING was added for coredumping, so it probably can now be
removed. But it doesn't hurt to keep.
Fixes: 9230738308 ("coredump: Don't perform any cleanups before dumping core")
Cc: stable@vger.kernel.org
Cc: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <kees@kernel.org>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/d89af63d478d6c64cc46a01420b46fd6eb147d6f.1735805772.git.namcao@linutronix.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
When utilized it dodges strlen() in vfs_readlink(), giving about 1.5%
speed up when issuing readlink on /initrd.img on ext4.
Filesystems opt in by calling inode_set_cached_link() when creating an
inode.
The size is stored in a new union utilizing the same space as i_devices,
thus avoiding growing the struct or taking up any more space.
Churn-wise the current readlink_copy() helper is patched to accept the
size instead of calculating it.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20241120112037.822078-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
The list of memory ranges for /proc/kcore is protected by a
rw_semaphore. We lock it for reading on every read from /proc/kcore.
This is very heavy, especially since it is rarely locked for writing.
Since we want to strongly favor read lock performance, convert it to a
percpu_rw_semaphore. I also experimented with percpu_ref and SRCU, but
this change was the simplest and the fastest.
In my benchmark, this reduces the time per read by yet another 20
nanoseconds on top of the previous two changes, from 195 nanoseconds per
read to 175.
Link: https://github.com/osandov/drgn/issues/106
Signed-off-by: Omar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/83a3b235b4bcc3b8aef7c533e0657f4d7d5d35ae.1731115587.git.osandov@fb.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
We maintain a list of memory ranges for /proc/kcore, which usually has
10-20 entries. Currently, every single read from /proc/kcore walks the
entire list in order to count the number of entries and compute some
offsets. These values only change when the list of memory ranges
changes, which is very rare (only when memory is hot(un)plugged). We can
cache the values when the list is populated to avoid these redundant
walks.
In my benchmark, this reduces the time per read by another 20
nanoseconds on top of the previous change, from 215 nanoseconds per read
to 195.
Link: https://github.com/osandov/drgn/issues/106
Signed-off-by: Omar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/8d945558b9c9efe74103a34b7780f1cd90d9ce7f.1731115587.git.osandov@fb.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
