mm/page_alloc: rename ALLOC_HIGH to ALLOC_MIN_RESERVE

Patch series "Discard __GFP_ATOMIC", v3.

Neil's patch has been residing in mm-unstable as commit 2fafb4fe8f7a ("mm:
discard __GFP_ATOMIC") for a long time and recently brought up again. 
Most recently, I was worried that __GFP_HIGH allocations could use
high-order atomic reserves which is unintentional but there was no
response so lets revisit -- this series reworks how min reserves are used,
protects highorder reserves and then finishes with Neil's patch with very
minor modifications so it fits on top.

There was a review discussion on renaming __GFP_DIRECT_RECLAIM to
__GFP_ALLOW_BLOCKING but I didn't think it was that big an issue and is
orthogonal to the removal of __GFP_ATOMIC.

There were some concerns about how the gfp flags affect the min reserves
but it never reached a solid conclusion so I made my own attempt.

The series tries to iron out some of the details on how reserves are used.
ALLOC_HIGH becomes ALLOC_MIN_RESERVE and ALLOC_HARDER becomes
ALLOC_NON_BLOCK and documents how the reserves are affected.  For example,
ALLOC_NON_BLOCK (no direct reclaim) on its own allows 25% of the min
reserve.  ALLOC_MIN_RESERVE (__GFP_HIGH) allows 50% and both combined
allows deeper access again.  ALLOC_OOM allows access to 75%.

High-order atomic allocations are explicitly handled with the caveat that
no __GFP_ATOMIC flag means that any high-order allocation that specifies
GFP_HIGH and cannot enter direct reclaim will be treated as if it was
GFP_ATOMIC.


This patch (of 6):

__GFP_HIGH aliases to ALLOC_HIGH but the name does not really hint what it
means.  As ALLOC_HIGH is internal to the allocator, rename it to
ALLOC_MIN_RESERVE to document that the min reserves can be depleted.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: NeilBrown <[email protected]>
Cc: Thierry Reding <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions