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94fa250ea5
commit a760542666 upstream.
The current behavior of memory failure is to truncate the page cache
regardless of dirty or clean. If the page is dirty the later access
will get the obsolete data from disk without any notification to the
users. This may cause silent data loss. It is even worse for shmem
since shmem is in-memory filesystem, truncating page cache means
discarding data blocks. The later read would return all zero.
The right approach is to keep the corrupted page in page cache, any
later access would return error for syscalls or SIGBUS for page fault,
until the file is truncated, hole punched or removed. The regular
storage backed filesystems would be more complicated so this patch is
focused on shmem. This also unblock the support for soft offlining
shmem THP.
[akpm@linux-foundation.org: coding style fixes]
[arnd@arndb.de: fix uninitialized variable use in me_pagecache_clean()]
Link: https://lkml.kernel.org/r/20211022064748.4173718-1-arnd@kernel.org
[Fix invalid pointer dereference in shmem_read_mapping_page_gfp() with a
slight different implementation from what Ajay Garg <ajaygargnsit@gmail.com>
and Muchun Song <songmuchun@bytedance.com> proposed and reworked the
error handling of shmem_write_begin() suggested by Linus]
Link: https://lore.kernel.org/linux-mm/20211111084617.6746-1-ajaygargnsit@gmail.com/
Link: https://lkml.kernel.org/r/20211020210755.23964-6-shy828301@gmail.com
Link: https://lkml.kernel.org/r/20211116193247.21102-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ajay Garg <ajaygargnsit@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Andy Lavr <andy.lavr@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
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.