This reverts commit 290434474c332a2ba9c8499fe699c7f2e1153280.

That commit broke cache=mmap, a mode that doesn't cache metadata,
but still has writeback cache.

In commit 290434474c33 ("fs/9p: Refresh metadata in d_revalidate
for uncached mode too") we considered metadata cache to be enough to
not look at the server, but in writeback cache too looking at the server
size would make the vfs consider the file has been truncated before the
data has been flushed out, making the following repro fail (nothing is
ever read back, the resulting file ends up with no data written)
```
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

char buf[4096];

int main(int argc, char *argv[])
{
        int ret, i;
        int fdw, fdr;

        if (argc < 2)
                return 1;

        fdw = openat(AT_FDCWD, argv[1], O_RDWR|O_CREAT|O_EXCL|O_CLOEXEC, 0600);
        if (fdw < 0) {
                fprintf(stderr, "cannot open fdw\n");
                return 1;
        }
        write(fdw, buf, sizeof(buf));

        fdr = openat(AT_FDCWD, argv[1], O_RDONLY|O_CLOEXEC);

        if (fdr < 0) {
                fprintf(stderr, "cannot open fdr\n");
                close(fdw);
                return 1;
        }

        for (i = 0; i < 10; i++) {
                ret = read(fdr, buf, sizeof(buf));
                fprintf(stderr, "i: %d, read returns %d\n", i, ret);
        }

        close(fdr);
        close(fdw);
        return 0;
}
```

There is a fix for this particular reproducer but it looks like there
are other problems around metadata refresh (e.g. around file rename), so
revert this to avoid d_revalidate in uncached mode for now.

Reported-by: Song Liu <song@kernel.org>
Link: https://lkml.kernel.org/r/CAHzjS_u_SYdt5=2gYO_dxzMKXzGMt-TfdE_ueowg-Hq5tRCAiw@mail.gmail.com
Reported-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Link: https://lore.kernel.org/bpf/CAEf4BzZbCE4tLoDZyUf_aASpgAGFj75QMfSXX4a4dLYixnOiLg@mail.gmail.com/
Fixes: 290434474c33 ("fs/9p: Refresh metadata in d_revalidate for uncached mode too")
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Pull 9p updates from Dominique Martinet:
 "A bunch of unrelated fixes:

   - polling fix for trans fd that ought to have been fixed otherwise
     back in March, but apparently came back somewhere else...

   - USB transport buffer overflow fix

   - Some dentry lifetime rework to handle metadata update for currently
     opened files in uncached mode, or inode type change in cached mode

   - a double-put on invalid flush found by syzbot

   - and finally /sys/fs/9p/caches not advancing buffer and overwriting
     itself for large contents

  Thanks to everyone involved!"

* tag '9p-for-6.18-rc1' of https://github.com/martinetd/linux:
  9p: sysfs_init: don't hardcode error to ENOMEM
  9p: fix /sys/fs/9p/caches overwriting itself
  9p: clean up comment typos
  9p/trans_fd: p9_fd_request: kick rx thread if EPOLLIN
  net/9p: fix double req put in p9_fd_cancelled
  net/9p: Fix buffer overflow in USB transport layer
  fs/9p: Add p9_debug(VFS) in d_revalidate
  fs/9p: Invalidate dentry if inode type change detected in cached mode
  fs/9p: Refresh metadata in d_revalidate for uncached mode too

Pull finish_no_open updates from Al Viro:
 "finish_no_open calling conventions change to simplify callers"

* tag 'pull-finish_no_open' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  slightly simplify nfs_atomic_open()
  simplify gfs2_atomic_open()
  simplify fuse_atomic_open()
  simplify nfs_atomic_open_v23()
  simplify vboxsf_dir_atomic_open()
  simplify cifs_atomic_open()
  9p: simplify v9fs_vfs_atomic_open_dotl()
  9p: simplify v9fs_vfs_atomic_open()
  allow finish_no_open(file, ERR_PTR(-E...))

v9fs_sysfs_init() always returned -ENOMEM on failure;
return the actual sysfs_create_group() error instead.

Signed-off-by: Randall P. Embry <rpembry@gmail.com>
Message-ID: <20250926-v9fs_misc-v1-3-a8b3907fc04d@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

caches_show() overwrote its buffer on each iteration,
so only the last cache tag was visible in sysfs output.

Properly append with snprintf(buf + count, …).

Signed-off-by: Randall P. Embry <rpembry@gmail.com>
Message-ID: <20250926-v9fs_misc-v1-2-a8b3907fc04d@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Fix a few minor typos in comments (e.g. "trasnport" → "transport").

Signed-off-by: Randall P. Embry <rpembry@gmail.com>
Message-ID: <20250926-v9fs_misc-v1-1-a8b3907fc04d@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

again, preexisting aliases will always be positive

Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

if v9fs_vfs_lookup() returns a preexisting alias, it is guaranteed to be
positive.  IOW, in that case we will immediately return finish_no_open(),
leaving only the case res == NULL past that point.

Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

generic_delete_inode() is rather misleading for what the routine is
doing. inode_just_drop() should be much clearer.

The new naming is inconsistent with generic_drop_inode(), so rename that
one as well with inode_ as the suffix.

No functional changes.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

This was a useful debugging / validation aid, and can explain why a
GETATTR request is made.

Signed-off-by: Tingmao Wang <m@maowtm.org>
Message-ID: <00829a99549e33d26139fa4d756c466629f13e00.1743956147.git.m@maowtm.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>