Skip to content
Commit 050dcb5c authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

huge tmpfs: fix fallocate(vanilla) advance over huge pages

Patch series "huge tmpfs: shmem_is_huge() fixes and cleanups".

A series of huge tmpfs fixes and cleanups.

This patch (of 9):

shmem_fallocate() goes to a lot of trouble to leave its newly allocated
pages !Uptodate, partly to identify and undo them on failure, partly to
leave the overhead of clearing them until later.  But the huge page case
did not skip to the end of the extent, walked through the tail pages one
by one, and appeared to work just fine: but in doing so, cleared and
Uptodated the huge page, so there was no way to undo it on failure.

And by setting Uptodate too soon, it messed up both its nr_falloced and
nr_unswapped counts, so that the intended "time to give up" heuristic did
not work at all.

Now advance immediately to the end of the huge extent, with a comment on
why this is more than just an optimization.  But although this speeds up
huge tmpfs fallocation, it does leave the clearing until first use, and
some users may have come to appreciate slow fallocate but fast first use:
if they complain, then we can consider adding a pass to clear at the end.

Link: https://lkml.kernel.org/r/da632211-8e3e-6b1-aee-ab24734429a0@google.com
Link: https://lkml.kernel.org/r/16201bd2-70e-37e2-e89b-5f929430da@google.com


Fixes: 800d8c63 ("shmem: add huge pages support")
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 86a2f3f2
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment