The helper functions v9fs_cache_register and v9fs_cache_unregister are
trivial helper functions that don't offer any extra functionality and
are unncessary. Replace them with direct calls to v9fs_init_inode_cache
and v9fs_destroy_inode_cache respectively to simplify the code.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Message-ID: <20241107095756.10261-1-colin.i.king@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Pull more 9p reverts from Dominique Martinet:
 "Revert patches causing inode collision problems.

  The code simplification introduced significant regressions on servers
  that do not remap inode numbers when exporting multiple underlying
  filesystems with colliding inodes. See the top-most revert (commit
  be2ca3825372) for details.

  This problem had been ignored for too long and the reverts will also
  head to stable (6.9+).

  I'm confident this set of patches gets us back to previous behaviour
  (another related patch had already been reverted back in April and
  we're almost back to square 1, and the rest didn't touch inode
  lifecycle)"

* tag '9p-for-6.12-rc5' of https://github.com/martinetd/linux:
  Revert "fs/9p: simplify iget to remove unnecessary paths"
  Revert "fs/9p: fix uaf in in v9fs_stat2inode_dotl"
  Revert "fs/9p: remove redundant pointer v9ses"
  Revert " fs/9p: mitigate inode collisions"

This reverts commit 724a08450f74b02bd89078a596fd24857827c012.

This code simplification introduced significant regressions on servers
that do not remap inode numbers when exporting multiple underlying
filesystems with colliding inodes, as can be illustrated with simple
tmpfs exports in qemu with remapping disabled:
```
# host side
cd /tmp/linux-test
mkdir m1 m2
mount -t tmpfs tmpfs m1
mount -t tmpfs tmpfs m2
mkdir m1/dir m2/dir
echo foo > m1/dir/foo
echo bar > m2/dir/bar

# guest side
# started with -virtfs local,path=/tmp/linux-test,mount_tag=tmp,security_model=mapped-file
mount -t 9p -o trans=virtio,debug=1 tmp /mnt/t

ls /mnt/t/m1/dir
# foo
ls /mnt/t/m2/dir
# bar (works ok if directry isn't open)

# cd to keep first dir's inode alive
cd /mnt/t/m1/dir
ls /mnt/t/m2/dir
# foo (should be bar)
```
Other examples can be crafted with regular files with fscache enabled,
in which case I/Os just happen to the wrong file leading to
corruptions, or guest failing to boot with:
  | VFS: Lookup of 'com.android.runtime' in 9p 9p would have caused loop

In theory, we'd want the servers to be smart enough and ensure they
never send us two different files with the same 'qid.path', but while
qemu has an option to remap that is recommended (and qemu prints a
warning if this case happens), there are many other servers which do
not (kvmtool, nfs-ganesha, probably diod...), we should at least ensure
we don't cause regressions on this:
- assume servers can't be trusted and operations that should get a 'new'
inode properly do so. commit d05dcfdf5e16 (" fs/9p: mitigate inode
collisions") attempted to do this, but v9fs_fid_iget_dotl() was not
called so some higher level of caching got in the way; this needs to be
fixed properly before we can re-apply the patches.
- if we ever want to really simplify this code, we will need to add some
negotiation with the server at mount time where the server could claim
they handle this properly, at which point we could optimize this out.
(but that might not be needed at all if we properly handle the 'new'
check?)

Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")
Reported-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/all/20240408141436.GA17022@redhat.com/
Link: https://lkml.kernel.org/r/20240923100508.GA32066@willie-the-truck
Cc: stable@vger.kernel.org # v6.9+
Message-ID: <20241024-revert_iget-v1-4-4cac63d25f72@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

This reverts commit 11763a8598f888dec631a8a903f7ada32181001f.

This is a requirement to revert commit 724a08450f74 ("fs/9p: simplify
iget to remove unnecessary paths"), see that revert for details.

Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")
Reported-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20240923100508.GA32066@willie-the-truck
Cc: stable@vger.kernel.org # v6.9+
Message-ID: <20241024-revert_iget-v1-3-4cac63d25f72@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

This reverts commit 10211b4a23cf4a3df5c11a10e5b3d371f16a906f.

This is a requirement to revert commit 724a08450f74 ("fs/9p: simplify
iget to remove unnecessary paths"), see that revert for details.

Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")
Reported-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20240923100508.GA32066@willie-the-truck
Cc: stable@vger.kernel.org # v6.9+
Message-ID: <20241024-revert_iget-v1-2-4cac63d25f72@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

This reverts commit d05dcfdf5e1659b2949d13060284eff3888b644e.

This is a requirement to revert commit 724a08450f74 ("fs/9p: simplify
iget to remove unnecessary paths"), see that revert for details.

Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")
Reported-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20240923100508.GA32066@willie-the-truck
Cc: stable@vger.kernel.org # v6.9+
Message-ID: <20241024-revert_iget-v1-1-4cac63d25f72@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

This reverts commit 1325e4a91a405f88f1b18626904d37860a4f9069.

using multipage folios apparently break some madvise operations like
MADV_PAGEOUT which do not reliably unload the specified page anymore,

Revert the patch until that is figured out.

Reported-by: Andrii Nakryiko <andrii@kernel.org>
Fixes: 1325e4a91a40 ("9p: Enable multipage folios")
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull 9p fixes from Dominique Martinet:
 "Mashed-up update that I sat on too long:

   - fix for multiple slabs created with the same name

   - enable multipage folios

   - theorical fix to also look for opened fids by inode if none was
     found by dentry"

[ Enabling multi-page folios should have been done during the merge
  window, but it's a one-liner, and the actual meat of the enablement
  is in netfs and already in use for other filesystems...  - Linus ]

* tag '9p-for-6.12-rc4' of https://github.com/martinetd/linux:
  9p: Avoid creating multiple slab caches with the same name
  9p: Enable multipage folios
  9p: v9fs_fid_find: also lookup by inode if not found dentry

Enable support for multipage folios on the 9P filesystem.  This is all
handled through netfslib and is already enabled on AFS and CIFS also.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric Van Hensbergen <ericvh@kernel.org>
cc: Latchesar Ionkov <lucho@ionkov.net>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Christian Schoenebeck <linux_oss@crudebyte.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: v9fs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Message-ID: <20240620173137.610345-7-dhowells@redhat.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

It's possible for v9fs_fid_find "find by dentry" branch to not turn up
anything despite having an entry set (because e.g. uid doesn't match),
in which case the calling code will generally make an extra lookup
to the server.

In this case we might have had better luck looking by inode, so fall
back to look up by inode if we have one and the lookup by dentry failed.

Message-Id: <20240523210024.1214386-1-asmadeus@codewreck.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>