On Fri, Aug 01, 2014 at 11:12:41AM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > When we need to modify the "ignore checksum error" behavior flag to > get us past a library call, it's possible that the library call can > result in other flag bits being changed. Therefore, it is not correct > to restore unconditionally the previous flags value, since this will > have unintended side effects on the other fs->flags; nor is it correct > to assume that we can unconditionally set (or clear) the "ignore csum > error" flag bit. Therefore, we must merge the previous value of the > "ignore csum error" flag with the value of flags after the call. > > Note that we want to leave checksum verification on as much as > possible because doing so exposes e2fsck bugs where two metadata > blocks are "sharing" the same disk block, and attempting to fix one > before relocating the other causes major filesystem damage. The > damage is much more obvious when a previously checked piece of > metadata suddenly fails in a subsequent pass. > > The modifications to the pass 2, 3, and 3A code are justified as > follows: When e2fsck encounters a block of directory entries and > cannot find the placeholder entry at the end that contains the > checksum, it will try to insert the placeholder. If that fails, it > will schedule the directory for a pass 3A reconstruction. Until that > happens, we don't want directory block writing (pass 2), block > iteration (pass 3), or block reading (pass 3A) to fail due to checksum > errors, because failing to find the placeholder is itself a checksum > verification error, which causes e2fsck to abort without fixing > anything. > > The e2fsck call to ext2fs_read_bitmaps must never fail due to a > checksum error because e2fsck subsequently (a) verifies the bitmaps > itself; or (b) decides that they don't match what has been observed, > and rewrites them. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Applied, thanks. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
