svn commit: r361287 - in head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

[Mark Johnston]

On Wed, May 20, 2020 at 06:29:23PM +0000, Mark Johnston wrote:
> Author: markj
> Date: Wed May 20 18:29:23 2020
> New Revision: 361287
> URL: https://svnweb.freebsd.org/changeset/base/361287
> 
> Log:
>   Don't block on the range lock in zfs_getpages().
>   
>   After r358443 the vnode object lock no longer synchronizes concurrent
>   zfs_getpages() and zfs_write() (which must update vnode pages to
>   maintain coherence).  This created a potential deadlock between ZFS
>   range locks and VM page busy locks: a fault on a mapped file will cause
>   the fault page to be busied, after which zfs_getpages() locks a range
>   around the file offset in order to map adjacent, resident pages;
>   zfs_write() locks the range first, and then must busy vnode pages when
>   synchronizing.
>   
>   Solve this by adding a non-blocking mode for ZFS range locks, and using
>   it in zfs_getpages().  If zfs_getpages() fails to acquire the range
>   lock, only the fault page will be populated.

I will work on getting this submitted to OpenZFS.