mm: cma: support sysfs

Since CMA is getting used more widely, it's more important to keep
monitoring CMA statistics for system health since it's directly related to
user experience.

This patch introduces sysfs statistics for CMA, in order to provide some
basic monitoring of the CMA allocator.

 * the number of CMA page successful allocations
 * the number of CMA page allocation failures

These two values allow the user to calcuate the allocation
failure rate for each CMA area.

e.g.)
  /sys/kernel/mm/cma/WIFI/alloc_pages_[success|fail]
  /sys/kernel/mm/cma/SENSOR/alloc_pages_[success|fail]
  /sys/kernel/mm/cma/BLUETOOTH/alloc_pages_[success|fail]

The cma_stat was intentionally allocated by dynamic allocation
to harmonize with kobject lifetime management.
https://lore.kernel.org/linux-mm/[email protected]/

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/linux-mm/[email protected]/
Signed-off-by: Minchan Kim <[email protected]>
Signed-off-by: Colin Ian King <[email protected]>

Tested-by: Dmitry Osipenko <[email protected]>
Reviewed-by: Dmitry Osipenko <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Tested-by: Anders Roxell <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: John Dias <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Colin Ian King <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions