During testing of raw block devices + DAX I noticed that the struct block_device that we were using for DAX operations was incorrect. For the fault handlers, etc. we can just get the correct bdev via get_block(), which is passed in as a function pointer, but for the *sync code and for sector zeroing we don't have access to get_block(). This is also an issue for XFS real-time devices, whenever we get those working. Patch one of this series fixes the DAX sector zeroing code by explicitly passing in a valid struct block_device. Patch two of this series fixes DAX *sync support by moving calls to dax_writeback_mapping_range() out of filemap_write_and_wait_range() and into the filesystem/block device ->writepages function so that it can supply us with a valid block device. This also fixes DAX code to properly flush caches in response to sync(2). Thanks to Jan Kara for his initial draft of patch 2: https://lkml.org/lkml/2016/2/9/485 Here are the changes that I've made to that patch: 1) For DAX mappings, only return after calling dax_writeback_mapping_range() if we encountered an error. In the non-error case we still need to write back normal pages, else we lose metadata updates. 2) In dax_writeback_mapping_range(), move the new check for if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL) above the i_blkbits check. In my testing I found cases where dax_writeback_mapping_range() was called for inodes with i_blkbits != PAGE_SHIFT - I'm assuming these are internal metadata inodes? They have no exceptional DAX entries to flush, so we have no work to do, but if we return error from the i_blkbits check we will fail the overall writeback operation. Please let me know if it seems wrong for us to be seeing inodes set to use DAX but with i_blkbits != PAGE_SHIFT and I'll get more info. 3) In filemap_write_and_wait() and filemap_write_and_wait_range(), continue the writeback in the case that DAX is enabled but we only have a nonzero mapping->nrpages. As with 1) and 2), I believe this is necessary to properly writeback metadata changes. If this sounds wrong, please let me know and I'll get more info. A working tree can be found here: https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=fsync_bdev_v2 Ross Zwisler (2): dax: supply DAX clearing code with correct bdev dax: move writeback calls into the filesystems fs/block_dev.c | 16 +++++++++++++++- fs/dax.c | 22 ++++++++++++---------- fs/ext2/inode.c | 17 +++++++++++++++-- fs/ext4/inode.c | 7 +++++++ fs/xfs/xfs_aops.c | 11 ++++++++++- fs/xfs/xfs_aops.h | 1 + fs/xfs/xfs_bmap_util.c | 3 ++- include/linux/dax.h | 8 +++++--- mm/filemap.c | 12 ++++-------- 9 files changed, 71 insertions(+), 26 deletions(-) -- 2.5.0 -- 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
