From: Dave Chinner <dchinner@xxxxxxxxxx> This reverts commit 61c6de667263184125d5ca75e894fcad632b0dd3. The reverted commit added page reference counting to iomap page structures that are used to track block size < page size state. This was supposed to align the code with page migration page accounting assumptions, but what it has done instead is break XFS filesystems. Every fstests run I've done on sub-page block size XFS filesystems has since picking up this commit 2 days ago has failed with bad page state errors such as: # ./run_check.sh "-m rmapbt=1,reflink=1 -i sparse=1 -b size=1k" "generic/038" .... SECTION -- xfs FSTYP -- xfs (debug) PLATFORM -- Linux/x86_64 test1 4.20.0-rc6-dgc+ MKFS_OPTIONS -- -f -m rmapbt=1,reflink=1 -i sparse=1 -b size=1k /dev/sdc MOUNT_OPTIONS -- /dev/sdc /mnt/scratch generic/038 454s ... run fstests generic/038 at 2018-12-20 18:43:05 XFS (sdc): Unmounting Filesystem XFS (sdc): Mounting V5 Filesystem XFS (sdc): Ending clean mount BUG: Bad page state in process kswapd0 pfn:3a7fa page:ffffea0000ccbeb0 count:0 mapcount:0 mapping:ffff88800d9b6360 index:0x1 flags: 0xfffffc0000000() raw: 000fffffc0000000 dead000000000100 dead000000000200 ffff88800d9b6360 raw: 0000000000000001 0000000000000000 00000000ffffffff page dumped because: non-NULL mapping CPU: 0 PID: 676 Comm: kswapd0 Not tainted 4.20.0-rc6-dgc+ #915 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1 04/01/2014 Call Trace: dump_stack+0x67/0x90 bad_page.cold.116+0x8a/0xbd free_pcppages_bulk+0x4bf/0x6a0 free_unref_page_list+0x10f/0x1f0 shrink_page_list+0x49d/0xf50 shrink_inactive_list+0x19d/0x3b0 shrink_node_memcg.constprop.77+0x398/0x690 ? shrink_slab.constprop.81+0x278/0x3f0 shrink_node+0x7a/0x2f0 kswapd+0x34b/0x6d0 ? node_reclaim+0x240/0x240 kthread+0x11f/0x140 ? __kthread_bind_mask+0x60/0x60 ret_from_fork+0x24/0x30 Disabling lock debugging due to kernel taint .... The failures are from anyway that frees pages and empties the per-cpu page magazines, so it's not a predictable failure or an easy to debug failure. generic/038 is a reliable reproducer of this problem - it has a 9 in 10 failure rate on one of my test machines. Failure on other machines have been at random points in fstests runs but every run has ended up tripping this problem. Hence generic/038 was used to bisect the failure because it was the most reliable failure. It is too close to the 4.20 release (not to mention holidays) to try to diagnose, fix and test the underlying cause of the problem, so reverting the commit is the only option we have right now. The revert has been tested against a current tot 4.20-rc7+ kernel across multiple machines running sub-page block size XFs filesystems and none of the bad page state failures have been seen. Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> --- fs/iomap.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/fs/iomap.c b/fs/iomap.c index 5bc172f3dfe8..d6bc98ae8d35 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -116,12 +116,6 @@ iomap_page_create(struct inode *inode, struct page *page) atomic_set(&iop->read_count, 0); atomic_set(&iop->write_count, 0); bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE); - - /* - * migrate_page_move_mapping() assumes that pages with private data have - * their count elevated by 1. - */ - get_page(page); set_page_private(page, (unsigned long)iop); SetPagePrivate(page); return iop; @@ -138,7 +132,6 @@ iomap_page_release(struct page *page) WARN_ON_ONCE(atomic_read(&iop->write_count)); ClearPagePrivate(page); set_page_private(page, 0); - put_page(page); kfree(iop); } -- 2.19.1
