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Brian Behlendorf
2092cf68d8
As part of vmalloc() a __pte_alloc_kernel() allocation may occur. This internal allocation does not honor the gfp flags passed to vmalloc(). This means even when vmalloc(GFP_NOFS) is called it is possible that a synchronous reclaim will occur. This reclaim can trigger file IO which can result in a deadlock. This issue can be avoided by explicitly setting PF_MEMALLOC on the process to subvert synchronous reclaim when vmalloc() is called with !__GFP_FS. An example stack of the deadlock can be found here (1), along with the upstream kernel bug (2), and the original bug discussion on the linux-mm mailing list (3). This code can be properly autoconf'ed when the upstream bug is fixed. 1) http://github.com/behlendorf/zfs/issues/labels/Vmalloc#issue/133 2) http://bugzilla.kernel.org/show_bug.cgi?id=30702 3) http://marc.info/?l=linux-mm&m=128942194520631&w=4
The Solaris Porting Layer (SPL) is a Linux kernel module which provides many of the Solaris kernel APIs. This shim layer makes it possible to run Solaris kernel code in the Linux kernel with relatively minimal modification. This can be particularly useful when you want to track upstream Solaris development closely and don’t want the overhead of maintaining a large patch which converts Solaris primitives to Linux primitives.
To build packages for your distribution:
$ ./configure
$ make pkg
Full documentation for building, configuring, and using the SPL can be found at: http://zfsonlinux.org