Unlock vmcore_mutex when returning -EBUSY.

Link: https://lkml.kernel.org/r/20250129222003.1495713-1-bvanassche@acm.org
Fixes: 0f3b1c40c652 ("fs/proc/vmcore: disallow vmcore modifications while the vmcore is open")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baoquan he <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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>

Let's factor it out into include/linux/crash_dump.h, from where we can
use it also outside of vmcore.c later.

Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-8-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Let's factor it out into include/linux/crash_dump.h, from where we can
use it also outside of vmcore.c later.

Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-7-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>

Let's use "vmcore: " as a prefix, converting the single "Kdump:
vmcore not initialized" one to effectively be "vmcore: not initialized".

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20241204125444.1734652-5-david@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>