[PATCH V4 0/3] Fix zone revalidation memory allocation failures

[Damien Le Moal <damien.lemoal@wdc.com>]

This series addresses a reccuring problem with zone revalidation
failures observed during extensive testing with memory constrained
system and device hot-plugging.

The problem source is failure to allocate large memory areas with
alloc_pages() or kmalloc() in blk_revalidate_disk_zones() to store the
disk array of zones (struct blk_zone) or in sd_zbc_report_zones() for
the report zones command reply buffer.

The solution proposed here is to:
1) limit the number of zones to be reported with a single report zones
command execution, and
2) Use vmalloc to allocate large-ish arrays and buffers in place of
alloc_pages() or kmalloc().

With these changes, tests do not show any zone revalidation failures
while not impacting the time taken for a disk zone inspection during
device scan and revalidation.

Changes from v3:
* Reworked use of flush_kernel_vmap_range() and
  invalidate_kernel_vmap_range() to contain the calls within bio.c,
  transparently to the user of bio_map_kern().
* Add similar support to bio_copy_kern().

Changes from v2:
* Move invalidate_kernel_vmap_range() of vmalloc-ed buffer to sd_zbc.c
  in patch 2, after completion of scsi_execute_req().
* In patch 2, add flush_kernel_vmap_range() before scsi_execute_req().

Changes from V1:
* Added call to invalidate_kernel_vmap_range() for vmalloc-ed buffers
  in patch 1.
* Fixed patch 2 compilation error with Sparc64 (kbuild robot)

Damien Le Moal (3):
  block: Allow mapping of vmalloc-ed buffers
  sd_zbc: Fix report zones buffer allocation
  block: Limit zone array allocation size

 block/bio.c            | 43 +++++++++++++++++++++-
 block/blk-zoned.c      | 29 +++++++--------
 drivers/scsi/sd_zbc.c  | 83 +++++++++++++++++++++++++++++++-----------
 include/linux/blkdev.h |  5 +++
 4 files changed, 122 insertions(+), 38 deletions(-)

-- 
2.21.0