Re: mm: WARNING in __delete_from_page_cache

[Williams, Dan J]

On Mon, 2016-01-25 at 13:22 +-0100, Jan Kara wrote:
+AFs-..+AF0-
+AD4- Thanks. Despite the huge list of recipients the author of the changes
+AD4- hasn't been CCed :) I've added Dan to CC since he wrote DAX support
+AD4- for
+AD4- block devices. It seems somehow the write didn't go through the DAX
+AD4- path
+AD4- but through the standard page cache write path. Ah, I see, only
+AD4- file-+AD4-f+AF8-mapping-+AD4-host has S+AF8-DAX set but io+AF8-is+AF8-direct() which decides
+AD4- whether DAX or pagecache path should be used for writes uses file-
+AD4- +AD4-f+AF8-inode
+AD4- which is something different for block devices...+AKA-

Thanks, yes, the following silences the warning for me:

8+ADw------ (git am --scissors)
Subject: fs, block: force direct-I/O for dax-enabled block devices

From: Dan Williams +ADw-dan.j.williams+AEA-intel.com+AD4-

Similar to the file I/O path, re-direct all I/O to the DAX path for I/O
to a block-device special file.

Otherwise, we confuse the DAX code that does not expect to find live
data in the page cache:

+AKAAoACgAKA-------------+AFs- cut here +AF0-------------
+AKAAoACgAKA-WARNING: CPU: 0 PID: 7676 at mm/filemap.c:217
+AKAAoACgAKAAXwBf-delete+AF8-from+AF8-page+AF8-cache+-0x9f6/0xb60()
+AKAAoACgAKA-Modules linked in:
+AKAAoACgAKA-CPU: 0 PID: 7676 Comm: a.out Not tainted 4.4.0+- +ACM-276
+AKAAoACgAKA-Hardware name: QEMU Standard PC (i440FX +- PIIX, 1996), BIOS Bochs 01/01/2011
+AKAAoACgAKAAoA-00000000ffffffff ffff88006d3f7738 ffffffff82999e2d 0000000000000000
+AKAAoACgAKAAoA-ffff8800620a0000 ffffffff86473d20 ffff88006d3f7778 ffffffff81352089
+AKAAoACgAKAAoA-ffffffff81658d36 ffffffff86473d20 00000000000000d9 ffffea0000009d60
+AKAAoACgAKA-Call Trace:
+AKAAoACgAKAAoABbADwAoACgAKAAoACg-inline+AKAAoACgAKAAoAA+AF0- +AF8AXw-dump+AF8-stack lib/dump+AF8-stack.c:15
+AKAAoACgAKAAoABbADw-ffffffff82999e2d+AD4AXQ- dump+AF8-stack+-0x6f/0xa2 lib/dump+AF8-stack.c:50
+AKAAoACgAKAAoABbADw-ffffffff81352089+AD4AXQ- warn+AF8-slowpath+AF8-common+-0xd9/0x140 kernel/panic.c:482
+AKAAoACgAKAAoABbADw-ffffffff813522b9+AD4AXQ- warn+AF8-slowpath+AF8-null+-0x29/0x30 kernel/panic.c:515
+AKAAoACgAKAAoABbADw-ffffffff81658d36+AD4AXQ- +AF8AXw-delete+AF8-from+AF8-page+AF8-cache+-0x9f6/0xb60 mm/filemap.c:217
+AKAAoACgAKAAoABbADw-ffffffff81658fb2+AD4AXQ- delete+AF8-from+AF8-page+AF8-cache+-0x112/0x200 mm/filemap.c:244
+AKAAoACgAKAAoABbADw-ffffffff818af369+AD4AXQ- +AF8AXw-dax+AF8-fault+-0x859/0x1800 fs/dax.c:487
+AKAAoACgAKAAoABbADw-ffffffff8186f4f6+AD4AXQ- blkdev+AF8-dax+AF8-fault+-0x26/0x30 fs/block+AF8-dev.c:1730
+AKAAoACgAKAAoABbADwAoACgAKAAoACg-inline+AKAAoACgAKAAoAA+AF0- wp+AF8-pfn+AF8-shared mm/memory.c:2208
+AKAAoACgAKAAoABbADw-ffffffff816e9145+AD4AXQ- do+AF8-wp+AF8-page+-0xc85/0x14f0 mm/memory.c:2307
+AKAAoACgAKAAoABbADwAoACgAKAAoACg-inline+AKAAoACgAKAAoAA+AF0- handle+AF8-pte+AF8-fault mm/memory.c:3323
+AKAAoACgAKAAoABbADwAoACgAKAAoACg-inline+AKAAoACgAKAAoAA+AF0- +AF8AXw-handle+AF8-mm+AF8-fault mm/memory.c:3417
+AKAAoACgAKAAoABbADw-ffffffff816ecec3+AD4AXQ- handle+AF8-mm+AF8-fault+-0x2483/0x4640 mm/memory.c:3446
+AKAAoACgAKAAoABbADw-ffffffff8127eff6+AD4AXQ- +AF8AXw-do+AF8-page+AF8-fault+-0x376/0x960 arch/x86/mm/fault.c:1238
+AKAAoACgAKAAoABbADw-ffffffff8127f738+AD4AXQ- trace+AF8-do+AF8-page+AF8-fault+-0xe8/0x420 arch/x86/mm/fault.c:1331
+AKAAoACgAKAAoABbADw-ffffffff812705c4+AD4AXQ- do+AF8-async+AF8-page+AF8-fault+-0x14/0xd0 arch/x86/kernel/kvm.c:264
+AKAAoACgAKAAoABbADw-ffffffff86338f78+AD4AXQ- async+AF8-page+AF8-fault+-0x28/0x30 arch/x86/entry/entry+AF8-64.S:986
+AKAAoACgAKAAoABbADw-ffffffff86336c36+AD4AXQ- entry+AF8-SYSCALL+AF8-64+AF8-fastpath+-0x16/0x7a
+AKAAoACgAKA-arch/x86/entry/entry+AF8-64.S:185
+AKAAoACgAKA----+AFs- end trace dae21e0f85f1f98c +AF0----

Cc: Matthew Wilcox +ADw-willy+AEA-linux.intel.com+AD4-
Cc: Ross Zwisler +ADw-ross.zwisler+AEA-linux.intel.com+AD4-
Fixes: 5a023cdba50c (+ACI-block: enable dax for raw block devices+ACI-)
Reported-by: Dmitry Vyukov +ADw-dvyukov+AEA-google.com+AD4-
Reported-by: Kirill A. Shutemov +ADw-kirill+AEA-shutemov.name+AD4-
Suggested-by: Jan Kara +ADw-jack+AEA-suse.cz+AD4-
Signed-off-by: Dan Williams +ADw-dan.j.williams+AEA-intel.com+AD4-
---
+AKA-fs/block+AF8-dev.c+AKAAoACgAKAAoAB8AKAAoACgAKA-5 -----
+AKA-include/linux/fs.h +AHwAoACgAKA-12 +-+-+-+-+-+-+-+-+-+-+--
+AKA-2 files changed, 11 insertions(+-), 6 deletions(-)

diff --git a/fs/block+AF8-dev.c b/fs/block+AF8-dev.c
index 7b9cd49622b1..277008617b2d 100644
--- a/fs/block+AF8-dev.c
+-+-+- b/fs/block+AF8-dev.c
+AEAAQA- -156,11 +-156,6 +AEAAQA- blkdev+AF8-get+AF8-block(struct inode +ACo-inode, sector+AF8-t iblock,
+AKA-	return 0+ADs-
+AKAAfQ-
+AKA-
-static struct inode +ACo-bdev+AF8-file+AF8-inode(struct file +ACo-file)
-+AHs-
-	return file-+AD4-f+AF8-mapping-+AD4-host+ADs-
-+AH0-
-
+AKA-static ssize+AF8-t
+AKA-blkdev+AF8-direct+AF8-IO(struct kiocb +ACo-iocb, struct iov+AF8-iter +ACo-iter, loff+AF8-t offset)
+AKAAew-
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1a2046275cdf..a4c4314eed48 100644
--- a/include/linux/fs.h
+-+-+- b/include/linux/fs.h
+AEAAQA- -1237,6 +-1237,11 +AEAAQA- static inline struct inode +ACo-file+AF8-inode(const struct file +ACo-f)
+AKA-	return f-+AD4-f+AF8-inode+ADs-
+AKAAfQ-
+AKA-
+-static inline struct inode +ACo-bdev+AF8-file+AF8-inode(struct file +ACo-file)
+-+AHs-
+-	return file-+AD4-f+AF8-mapping-+AD4-host+ADs-
+-+AH0-
+-
+AKA-static inline int locks+AF8-lock+AF8-file+AF8-wait(struct file +ACo-filp, struct file+AF8-lock +ACo-fl)
+AKAAew-
+AKA-	return locks+AF8-lock+AF8-inode+AF8-wait(file+AF8-inode(filp), fl)+ADs-
+AEAAQA- -2907,7 +-2912,12 +AEAAQA- extern void replace+AF8-mount+AF8-options(struct super+AF8-block +ACo-sb, char +ACo-options)+ADs-
+AKA-
+AKA-static inline bool io+AF8-is+AF8-direct(struct file +ACo-filp)
+AKAAew-
-	return (filp-+AD4-f+AF8-flags +ACY- O+AF8-DIRECT) +AHwAfA- IS+AF8-DAX(file+AF8-inode(filp))+ADs-
+-	struct inode +ACo-inode +AD0- file+AF8-inode(filp)+ADs-
+-
+-	if (S+AF8-ISBLK(inode-+AD4-i+AF8-mode))
+-		inode +AD0- bdev+AF8-file+AF8-inode(filp)+ADs-
+-
+-	return (filp-+AD4-f+AF8-flags +ACY- O+AF8-DIRECT) +AHwAfA- IS+AF8-DAX(inode)+ADs-
+AKAAfQ-
+AKA-
+AKA-static inline int iocb+AF8-flags(struct file +ACo-file)