erofs: hold real inodes for shared files

EROFS page cache sharing uses shared inodes. However, a mmaped VMA
keeps the shared file even after the corresponding fd is closed, while
currently the real inode is never held by any reference associated
with the shared file.

As a result, the real inode could be evicted and removed from the
shared inode's list while the page fault can still invoke on the
shared inode's address space, which causes no candidate is
successfully acquired by erofs_real_inode().

Fix this by simply keeping the original inode in the shared backing
file's private data.

Also replace confusing "realfile"/"rf" names with "sf" (sharedfile)
to unify the terms as well as nullify realinode in erofs_real_inode()
to avoid returning an uninitialized pointer.

Fixes: 5ef3208e3be5 ("erofs: introduce the page cache share feature")
Reported-by: YoungWoo Rim <xsapiens75@gmail.com>
Closes: https://lore.kernel.org/r/atzSVuvqYKgmvDmO@MacBookPro
Cc: stable@vger.kernel.org # 7.0+
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang (Docker) <xiang@kernel.org>

0 files changed, 0 insertions, 0 deletions