On Sun, 28 Oct 2018 at 22:44, Richard Weinberger richard@nod.at wrote:
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: 474b93704f32 ("ubifs: Implement O_TMPFILE") Cc: stable@vger.kernel.org Reported-by: Russell Senior russell@personaltelco.net Reported-by: Rafał Miłecki zajec5@gmail.com Signed-off-by: Richard Weinberger richard@nod.at
Thank you Richard!!!
Tested-by: Rafał Miłecki rafal@milecki.pl