On 26.02.21 04:59, michael.christie@oracle.com wrote:

On 2/24/21 12:53 PM, Bodo Stroesser wrote:

quoted

This small series is based on Martin's for-next.

Future patches will need something like the - meanwhile removed -
radix_tree_for_each_contig macro.
Since general direction is to use xarray as replacement for
radix_tree and IDR, instead of re-introducing or open coding the
removed macro, with this series we switch over to xarray API.
Based on xarray a future patch easily can implement an analog
to radix_tree_for_each_contig.

Bodo Stroesser (2):
   scsi: target: tcmu: Replace IDR by XArray
   scsi: target: tcmu: Replace radix_tree with XArray

  drivers/target/target_core_user.c | 64 +++++++++++++++++++--------------------
  1 file changed, 31 insertions(+), 33 deletions(-)

Looks ok to me.

Reviewed-by: Mike Christie <michael.christie@oracle.com>

I think in a separate patch we need to change:

+		if (xa_store(&udev->data_blocks, dbi, page, GFP_KERNEL))
  			goto err_insert;

to GFP_NOIO. There were some users doing tcm loop  + tcmu and
were hitting issues when GFP_KERNEL lead to write backs back on
to the same tcmu device. We tried to change all the gfp flags but
we missed that one, because it was hidden in the radix tree's
xa_flags.

But then, for consistency reasons, shouldn't we change

+	if (xa_alloc(&udev->commands, &cmd_id, tcmu_cmd, XA_LIMIT(1, 0xffff),
+		     GFP_NOWAIT) < 0) {

to GFP_NOIO also?

Additionally I have to change memory allocation in tcmu_tmr_notify from
GFP_KERNEL to GFP_NOIO, since it happens while holding cmdr_lock mutex,
which could also cause the problems you desribed.

Shouldn't we better change to new API memalloc_noio_save and
memalloc_noio_restore in that new patch?