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commite58725d51fupstream. UBIFS's recovery code strictly assumes that a deleted inode will never come back, therefore it removes all data which belongs to that inode as soon it faces an inode with link count 0 in the replay list. Before O_TMPFILE this assumption was perfectly fine. With O_TMPFILE it can lead to data loss upon a power-cut. Consider a journal with entries like: 0: inode X (nlink = 0) /* O_TMPFILE was created */ 1: data for inode X /* Someone writes to the temp file */ 2: inode X (nlink = 0) /* inode was changed, xattr, chmod, … */ 3: inode X (nlink = 1) /* inode was re-linked via linkat() */ Upon replay of entry #2 UBIFS will drop all data that belongs to inode X, this will lead to an empty file after mounting. As solution for this problem, scan the replay list for a re-link entry before dropping data. Fixes:474b93704f("ubifs: Implement O_TMPFILE") Cc: stable@vger.kernel.org # 4.9-4.18 Cc: Russell Senior <russell@personaltelco.net> Cc: Rafał Miłecki <zajec5@gmail.com> Reported-by: Russell Senior <russell@personaltelco.net> Reported-by: Rafał Miłecki <zajec5@gmail.com> Tested-by: Rafał Miłecki <rafal@milecki.pl> Signed-off-by: Richard Weinberger <richard@nod.at> [rmilecki: update ubifs_assert() calls to compile with 4.18 and older] Signed-off-by: Rafał Miłecki <rafal@milecki.pl> (cherry picked from commite58725d51f) Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.