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.

Reported by:	bdrewery
Reviewed by:	avg
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D24839

0 files changed, 0 insertions, 0 deletions