Re: [PATCH RFC 0/2] Btrfs: fix file data corruptions due to lost dirty bits

[David Sterba <dsterba@suse.cz>]

On Wed, Jun 20, 2018 at 03:48:08PM -0400, Chris Mason wrote:
> 
> 
> On 20 Jun 2018, at 15:33, David Sterba wrote:
> 
> > On Wed, Jun 20, 2018 at 07:56:10AM -0700, Chris Mason wrote:
> >> We've been hunting the root cause of data crc errors here at FB for a 
> >> while.
> >> We'd find one or two corrupted files, usually displaying crc errors 
> >> without any
> >> corresponding IO errors from the storage.  The bug was rare enough 
> >> that we'd
> >> need to watch a large number of machines for a few days just to catch 
> >> it
> >> happening.
> >>
> >> We're still running these patches through testing, but the fixup 
> >> worker bug
> >> seems to account for the vast majority of crc errors we're seeing in 
> >> the fleet.
> >> It's cleaning pages that were dirty, and creating a window where they 
> >> can be
> >> reclaimed before we finish processing the page.
> >
> > I'm having flashbacks when I see 'fixup worker',
> 
> Yeah, I don't understand how so much pain can live in one little 
> function.
> 
> > and the test generic/208 does not make it better:
> >
> > generic/095		[18:07:03][ 3769.317862] run fstests generic/095 at 
> > 2018-06-20 18:07:03
> 
> Hmpf, I pass both 095 and 208 here.
> 
> > [ 3774.849685] BTRFS: device fsid 3acffad9-28e5-43ce-80e1-f5032e334cba 
> > devid 1 transid 5 /dev/vdb
> > [ 3774.875409] BTRFS info (device vdb): disk space caching is enabled
> > [ 3774.877723] BTRFS info (device vdb): has skinny extents
> > [ 3774.879371] BTRFS info (device vdb): flagging fs with big metadata 
> > feature
> > [ 3774.885020] BTRFS info (device vdb): checking UUID tree
> > [ 3775.593329] Page cache invalidation failure on direct I/O.  
> > Possible data corruption due to collision with buffered I/O!
> > [ 3775.596979] File: /tmp/scratch/file2 PID: 12031 Comm: kworker/1:1
> > [ 3776.642812] Page cache invalidation failure on direct I/O.  
> > Possible data corruption due to collision with buffered I/O!
> > [ 3776.645041] File: /tmp/scratch/file2 PID: 12033 Comm: kworker/3:0
> > [ 3776.920634] WARNING: CPU: 0 PID: 12036 at fs/btrfs/inode.c:9319 
> > btrfs_destroy_inode+0x1d5/0x290 [btrfs]
> 
> 
> Which warning is this in your tree?  The file_write patch is more likely 
> to have screwed up our bits and the fixup worker is more likely to have 
> screwed up nrpages.

 9311 void btrfs_destroy_inode(struct inode *inode)
 9312 {
 9313         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 9314         struct btrfs_ordered_extent *ordered;
 9315         struct btrfs_root *root = BTRFS_I(inode)->root;
 9316
 9317         WARN_ON(!hlist_empty(&inode->i_dentry));
 9318         WARN_ON(inode->i_data.nrpages);
 9319         WARN_ON(BTRFS_I(inode)->block_rsv.reserved);

The branch is the last pull, ie. no other 4.18-rc1 stuff plus your two patches.