18a937076c
If exclusive loads are enabled for zswap, we invalidate the entry before
returning from zswap_frontswap_load(), after dropping the local reference.
However, the tree lock is dropped during decompression after the local
reference is acquired, so the entry could be invalidated before we drop
the local ref. If this happens, the entry is freed once we drop the local
ref, and zswap_invalidate_entry() tries to invalidate an already freed
entry.
Fix this by:
(a) Making sure zswap_invalidate_entry() is always called with a local
ref held, to avoid being called on a freed entry.
(b) Making sure zswap_invalidate_entry() only drops the ref if the entry
was actually on the rbtree. Otherwise, another invalidation could
have already happened, and the initial ref is already dropped.
With these changes, there is no need to check that there is no need to
make sure the entry still exists in the tree in zswap_reclaim_entry()
before invalidating it, as zswap_reclaim_entry() will make this check
internally.
Link: https://lkml.kernel.org/r/20230621093009.637544-1-yosryahmed@google.com
Fixes: b9c91c43412f ("mm: zswap: support exclusive loads")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.