iomap: Revert "fs/iomap.c: get/put the page in iomap_page_create/release()"

3 files changed, 116 insertions, 0 deletions

diff --git a/debian/changelog b/debian/changelog
index 1b934dadb0de..e2b3b84fc619 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -207,6 +207,10 @@ linux (4.19.12-1) UNRELEASED; urgency=medium
   [ Bastian Blank ]
   * Ignore various ABI changes.
 
+  [ Salvatore Bonaccorso ]
+  * iomap: Revert "fs/iomap.c: get/put the page in
+    iomap_page_create/release()"
+
  -- Uwe Kleine-König <ukleinek@debian.org>  Mon, 17 Dec 2018 11:27:32 +0100
 
 linux (4.19.9-1) unstable; urgency=medium
diff --git a/debian/patches/bugfix/all/iomap-Revert-fs-iomap.c-get-put-the-page-in-iomap_pa.patch b/debian/patches/bugfix/all/iomap-Revert-fs-iomap.c-get-put-the-page-in-iomap_pa.patch
new file mode 100644
index 000000000000..aa52bfe4a5d6
--- /dev/null
+++ b/debian/patches/bugfix/all/iomap-Revert-fs-iomap.c-get-put-the-page-in-iomap_pa.patch
@@ -0,0 +1,111 @@
+From: Dave Chinner <dchinner@redhat.com>
+Date: Thu, 20 Dec 2018 23:23:24 +1100
+Subject: iomap: Revert "fs/iomap.c: get/put the page in
+ iomap_page_create/release()"
+Origin: https://git.kernel.org/linus/a837eca2412051628c0529768c9bc4f3580b040e
+
+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@redhat.com>
+Cc: Piotr Jaroszynski <pjaroszynski@nvidia.com>
+Cc: Christoph Hellwig <hch@lst.de>
+Cc: William Kucharski <william.kucharski@oracle.com>
+Cc: Darrick J. Wong <darrick.wong@oracle.com>
+Cc: Brian Foster <bfoster@redhat.com>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ 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);
+ }
+ 
+-- 
+2.20.1
+
diff --git a/debian/patches/series b/debian/patches/series
index 113ea15706a1..6fbb42978da1 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -98,6 +98,7 @@ bugfix/all/fs-add-module_softdep-declarations-for-hard-coded-cr.patch
 bugfix/all/partially-revert-usb-kconfig-using-select-for-usb_co.patch
 bugfix/all/kbuild-include-addtree-remove-quotes-before-matching-path.patch
 debian/revert-objtool-fix-config_stack_validation-y-warning.patch
+bugfix/all/iomap-Revert-fs-iomap.c-get-put-the-page-in-iomap_pa.patch
 
 # Miscellaneous features