Illumos 5027 - zfs large block support

5027 zfs large block support
Reviewed by: Alek Pinchuk <[email protected]>
Reviewed by: George Wilson <[email protected]>
Reviewed by: Josef 'Jeff' Sipek <[email protected]>
Reviewed by: Richard Elling <[email protected]>
Reviewed by: Saso Kiselkov <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Approved by: Dan McDonald <[email protected]>

References:
  https://www.illumos.org/issues/5027
  https://github.com/illumos/illumos-gate/commit/b515258

Porting Notes:

* Included in this patch is a tiny ISP2() cleanup in zio_init() from
Illumos 5255.

* Unlike the upstream Illumos commit this patch does not impose an
arbitrary 128K block size limit on volumes.  Volumes, like filesystems,
are limited by the zfs_max_recordsize=1M module option.

* By default the maximum record size is limited to 1M by the module
option zfs_max_recordsize.  This value may be safely increased up to
16M which is the largest block size supported by the on-disk format.
At the moment, 1M blocks clearly offer a significant performance
improvement but the benefits of going beyond this for the majority
of workloads are less clear.

* The illumos version of this patch increased DMU_MAX_ACCESS to 32M.
This was determined not to be large enough when using 16M blocks
because the zfs_make_xattrdir() function will fail (EFBIG) when
assigning a TX.  This was immediately observed under Linux because
all newly created files must have a security xattr created and
that was failing.  Therefore, we've set DMU_MAX_ACCESS to 64M.

* On 32-bit platforms a hard limit of 1M is set for blocks due
to the limited virtual address space.  We should be able to relax
this one the ABD patches are merged.

Ported-by: Brian Behlendorf <[email protected]>
Closes #354

1 files changed, 4 insertions, 5 deletions

diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index 59f73776c..e86b21aee 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -188,10 +188,9 @@ static void
 blksz_changed_cb(void *arg, uint64_t newval)
 {
 	zfs_sb_t *zsb = arg;
-
-	if (newval < SPA_MINBLOCKSIZE ||
-	    newval > SPA_MAXBLOCKSIZE || !ISP2(newval))
-		newval = SPA_MAXBLOCKSIZE;
+	ASSERT3U(newval, <=, spa_maxblocksize(dmu_objset_spa(zsb->z_os)));
+	ASSERT3U(newval, >=, SPA_MINBLOCKSIZE);
+	ASSERT(ISP2(newval));
 
 	zsb->z_max_blksz = newval;
 }
@@ -672,7 +671,7 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
 	 */
 	zsb->z_sb = NULL;
 	zsb->z_parent = zsb;
-	zsb->z_max_blksz = SPA_MAXBLOCKSIZE;
+	zsb->z_max_blksz = SPA_OLD_MAXBLOCKSIZE;
 	zsb->z_show_ctldir = ZFS_SNAPDIR_VISIBLE;
 	zsb->z_os = os;