On Wed, Nov 04, 2015 at 05:18:31PM +0100, Jan Kara wrote: > Hello, > > Another version of my ext4 fixes. I've fixed up all the failures Ted reported > except for ext4/001 failures which are false positive (will send fixes for that > test shortly) and generic/269 in nodelalloc mode which I just wasn't able to > reproduce. > > Note that testing with 1 KB blocksize on ramdisk is broken since brd has > buggy discard implementation. It took me quite some time to figure this out. > Fix is submitted but bear this in mind just in case. > > Changes since v2: > * Fixed collaps range to truncate pagecache properly with blocksize < pagesize > * Fixed assertion in ext4_get_blocks_overwrite > > Patch set description > > This series fixes a long standing problem of racing punch hole and page fault > resulting in possible filesystem corruption or stale data exposure. We fix the > problem by using a new inode-private rw_semaphore i_mmap_sem to synchronize > page faults with truncate and punch hole operations. > > When having this exclusion, the only remaining problem with DAX implementation > are races between two page faults zeroing out same block concurrently (where > the data written after the first fault finishes are possibly overwritten by > the second fault still doing zeroing). > > Patch 1 introduces i_mmap_sem lock in ext4 inode and uses it to properly > serialize extent manipulation operations and page faults. > > Patch 2 is mostly a preparatory cleanup patch which also avoids double lock / > unlock in unlocked DIO protections (currently harmless but nasty surprise). > > Patches 3-4 fix further races of extent manipulation functions (such as zero > range, collapse range, insert range) with buffered IO, page writeback > > Patch 5 documents locking order of ext4 filesystem locks. > > Patch 6 removes locking abuse of i_data_sem from the get_blocks() path when > dioread_nolock is enabled since it is not needed anymore. > > Patches 7-9 implement allocation of pre-zeroed blocks in ext4_map_blocks() > callback and use such blocks for allocations from DAX page faults. > > The patches survived xfstests run both in dax and non-dax mode. > > Honza This passed all my testing as well. Tested-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> -- 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
