BMC/Intel-BMC/linux.git/fs/dax.c, branch dev-4.4

dax: disable pmd mappings

2015-11-17T07:54:45+00:00

While dax pmd mappings are functional in the nominal path they trigger kernel crashes in the following paths: BUG: unable to handle kernel paging request at ffffea0004098000 IP: [] follow_trans_huge_pmd+0x117/0x3b0 [..] Call Trace: [] follow_page_mask+0x2d3/0x380 [] __get_user_pages+0xe8/0x6f0 [] get_user_pages_unlocked+0x165/0x1e0 [] get_user_pages_fast+0xa1/0x1b0 kernel BUG at arch/x86/mm/gup.c:131! [..] Call Trace: [] gup_pud_range+0x1bc/0x220 [] get_user_pages_fast+0x124/0x1b0 BUG: unable to handle kernel paging request at ffffea0004088000 IP: [] copy_huge_pmd+0x159/0x350 [..] Call Trace: [] copy_page_range+0x34c/0x9f0 [] copy_process+0x1b7f/0x1e10 [] _do_fork+0x91/0x590 All of these paths are interpreting a dax pmd mapping as a transparent huge page and making the assumption that the pfn is covered by the memmap, i.e. that the pfn has an associated struct page. PTE mappings do not suffer the same fate since they have the _PAGE_SPECIAL flag to cause the gup path to fault. We can do something similar for the PMD path, or otherwise defer pmd support for cases where a struct page is available. For now, 4.4-rc and -stable need to disable dax pmd support by default. For development the "depends on BROKEN" line can be removed from CONFIG_FS_DAX_PMD. Cc: Cc: Jan Kara Cc: Dave Chinner Cc: Matthew Wilcox Cc: Kirill A. Shutemov Reported-by: Ross Zwisler Signed-off-by: Dan Williams

Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

2015-11-14T01:35:48+00:00

Pull libnvdimm fixes from Dan Williams: - three fixes tagged for -stable including a crash fix, simple performance tweak, and an invalid i/o error. - build regression fix for the nvdimm unit tests - nvdimm documentation update * 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: dax: fix __dax_pmd_fault crash libnvdimm: documentation clarifications libnvdimm, pmem: fix size trim in pmem_direct_access() libnvdimm, e820: fix numa node for e820-type-12 pmem ranges tools/testing/nvdimm, acpica: fix flag rename build breakage

dax: fix __dax_pmd_fault crash

2015-11-13T02:33:54+00:00

Since 4.3 introduced devm_memremap_pages() the pfns handled by DAX may optionally have a struct page backing. When a mapped pfn reaches vmf_insert_pfn_pmd() it fails with a crash signature like the following: kernel BUG at mm/huge_memory.c:905! [..] Call Trace: [] __dax_pmd_fault+0x2ea/0x5b0 [] xfs_filemap_pmd_fault+0x92/0x150 [xfs] [] handle_mm_fault+0x312/0x1b50 Fix this by falling back to 4K mappings in the pfn_valid() case. Longer term, vmf_insert_pfn_pmd() needs to grow support for architectures that can provide a 'pmd_special' capability. Cc: Cc: Andrew Morton Reported-by: Ross Zwisler Signed-off-by: Dan Williams

Merge branch 'for-linus' of git://git.kernel.dk/linux-block

2015-11-12T23:54:30+00:00

Pull misc block fixes from Jens Axboe: "Stuff that got collected after the merge window opened. This contains: - NVMe: - Fix for non-striped transfer size setting for NVMe from Sathyavathi. - (Some) support for the weird Apple nvme controller in the macbooks. From Stephan Günther. - The error value leak for dax from Al. - A few minor blk-mq tweaks from me. - Add the new linux-block@vger.kernel.org mailing list to the MAINTAINERS file. - Discard fix for brd, from Jan. - A kerneldoc warning for block core from Randy. - An older fix from Vivek, converting a WARN_ON() to a rate limited printk when a device is hot removed with dirty inodes" * 'for-linus' of git://git.kernel.dk/linux-block: block: don't hardcode blk_qc_t -> tag mask dax_io(): don't let non-error value escape via retval instead of EFAULT block: fix blk-core.c kernel-doc warning fs/block_dev.c: Remove WARN_ON() when inode writeback fails NVMe: add support for Apple NVMe controller NVMe: use split lo_hi_{read,write}q blk-mq: mark __blk_mq_complete_request() static MAINTAINERS: add reference to new linux-block list NVMe: Increase the max transfer size when mdts is 0 brd: Refuse improperly aligned discard requests

Merge tag 'xfs-for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs

2015-11-12T04:18:48+00:00

Pull xfs updates from Dave Chinner: "There is nothing really major here - the only significant addition is the per-mount operation statistics infrastructure. Otherwises there's various ACL, xattr, DAX, AIO and logging fixes, and a smattering of small cleanups and fixes elsewhere. Summary: - per-mount operational statistics in sysfs - fixes for concurrent aio append write submission - various logging fixes - detection of zeroed logs and invalid log sequence numbers on v5 filesystems - memory allocation failure message improvements - a bunch of xattr/ACL fixes - fdatasync optimisation - miscellaneous other fixes and cleanups" * tag 'xfs-for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs: (39 commits) xfs: give all workqueues rescuer threads xfs: fix log recovery op header validation assert xfs: Fix error path in xfs_get_acl xfs: optimise away log forces on timestamp updates for fdatasync xfs: don't leak uuid table on rmmod xfs: invalidate cached acl if set via ioctl xfs: Plug memory leak in xfs_attrmulti_attr_set xfs: Validate the length of on-disk ACLs xfs: invalidate cached acl if set directly via xattr xfs: xfs_filemap_pmd_fault treats read faults as write faults xfs: add ->pfn_mkwrite support for DAX xfs: DAX does not use IO completion callbacks xfs: Don't use unwritten extents for DAX xfs: introduce BMAPI_ZERO for allocating zeroed extents xfs: fix inode size update overflow in xfs_map_direct() xfs: clear PF_NOFREEZE for xfsaild kthread xfs: fix an error code in xfs_fs_fill_super() xfs: stats are no longer dependent on CONFIG_PROC_FS xfs: simplify /proc teardown & error handling xfs: per-filesystem stats counter implementation ...

dax_io(): don't let non-error value escape via retval instead of EFAULT

2015-11-11T16:36:57+00:00

Signed-off-by: Al Viro Reported-by: Sasha Levin Cc: stable@vger.kernel.org # 4.0+ Signed-off-by: Jens Axboe

xfs: Don't use unwritten extents for DAX

2015-11-03T01:37:00+00:00

DAX has a page fault serialisation problem with block allocation. Because it allows concurrent page faults and does not have a page lock to serialise faults to the same page, it can get two concurrent faults to the page that race. When two read faults race, this isn't a huge problem as the data underlying the page is not changing and so "detect and drop" works just fine. The issues are to do with write faults. When two write faults occur, we serialise block allocation in get_blocks() so only one faul will allocate the extent. It will, however, be marked as an unwritten extent, and that is where the problem lies - the DAX fault code cannot differentiate between a block that was just allocated and a block that was preallocated and needs zeroing. The result is that both write faults end up zeroing the block and attempting to convert it back to written. The problem is that the first fault can zero and convert before the second fault starts zeroing, resulting in the zeroing for the second fault overwriting the data that the first fault wrote with zeros. The second fault then attempts to convert the unwritten extent, which is then a no-op because it's already written. Data loss occurs as a result of this race. Because there is no sane locking construct in the page fault code that we can use for serialisation across the page faults, we need to ensure block allocation and zeroing occurs atomically in the filesystem. This means we can still take concurrent page faults and the only time they will serialise is in the filesystem mapping/allocation callback. The page fault code will always see written, initialised extents, so we will be able to remove the unwritten extent handling from the DAX code when all filesystems are converted. Signed-off-by: Dave Chinner Reviewed-by: Brian Foster Signed-off-by: Dave Chinner

mm, dax: fix DAX deadlocks

2015-10-16T18:42:28+00:00

The following two locking commits in the DAX code: commit 843172978bb9 ("dax: fix race between simultaneous faults") commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX") introduced a number of deadlocks and other issues which need to be fixed for the v4.3 kernel. The list of issues in DAX after these commits (some newly introduced by the commits, some preexisting) can be found here: https://lkml.org/lkml/2015/9/25/602 (Subject: "Re: [PATCH] dax: fix deadlock in __dax_fault"). This undoes most of the changes introduced by those two commits, essentially returning us to the DAX locking scheme that was used in v4.2. Signed-off-by: Ross Zwisler Cc: Alexander Viro Cc: Dan Williams Tested-by: Dave Chinner Cc: Jan Kara Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

dax: fix NULL pointer in __dax_pmd_fault()

2015-10-02T01:42:35+00:00

Commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX") moved some code in __dax_pmd_fault() that was responsible for zeroing newly allocated PMD pages. The new location didn't properly set up 'kaddr', so when run this code resulted in a NULL pointer BUG. Fix this by getting the correct 'kaddr' via bdev_direct_access(). Signed-off-by: Ross Zwisler Reported-by: Dan Williams Reviewed-by: Dan Williams Cc: Alexander Viro Cc: Matthew Wilcox Cc: "Kirill A. Shutemov" Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

dax: fix O_DIRECT I/O to the last block of a blockdev

2015-09-16T00:07:35+00:00

commit bbab37ddc20b (block: Add support for DAX reads/writes to block devices) caused a regression in mkfs.xfs. That utility sets the block size of the device to the logical block size using the BLKBSZSET ioctl, and then issues a single sector read from the last sector of the device. This results in the dax_io code trying to do a page-sized read from 512 bytes from the end of the device. The result is -ERANGE being returned to userspace. The fix is to align the block to the page size before calling get_block. Thanks to willy for simplifying my original patch. Cc: Signed-off-by: Jeff Moyer Tested-by: Linda Knippers Signed-off-by: Dan Williams