ba60fdf75e
commit 3a75cb05d53f4a6823a32deb078de1366954a804 upstream. In cachestat, we access the folio from the page cache's xarray to compute its page offset, and check for its dirty and writeback flags. However, we do not hold a reference to the folio before performing these actions, which means the folio can concurrently be released and reused as another folio/page/slab. Get around this altogether by just using xarray's existing machinery for the folio page offsets and dirty/writeback states. This changes behavior for tmpfs files to now always report zeroes in their dirty and writeback counters. This is okay as tmpfs doesn't follow conventional writeback cache behavior: its pages get "cleaned" during swapout, after which they're no longer resident etc. Link: https://lkml.kernel.org/r/20240220153409.GA216065@cmpxchg.org Fixes: cf264e1329fb ("cachestat: implement cachestat syscall") Reported-by: Jann Horn <jannh@google.com> Suggested-by: Matthew Wilcox <willy@infradead.org> Signed-off-by: Nhat Pham <nphamcs@gmail.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Jann Horn <jannh@google.com> Cc: <stable@vger.kernel.org> [6.4+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.