The patch titled
Subject: jbd2: get rid of superfluous __GFP_REPEAT
has been added to the -mm tree. Its filename is
jbd2-get-rid-of-superfluous-__gfp_repeat.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/jbd2-get-rid-of-superfluous-__gfp_repeat.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/jbd2-get-rid-of-superfluous-__gfp_repeat.patch
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: jbd2: get rid of superfluous __GFP_REPEAT
jbd2_alloc is explicit about its allocation preferences wrt. the
allocation size. Sub page allocations go to the slab allocator
and larger are using either the page allocator or vmalloc. This
is all good but the logic is unnecessarily complex.
1) as per Ted, the vmalloc fallback is a left-over:
: jbd2_alloc is only passed in the bh->b_size, which can't be PAGE_SIZE, so
: the code path that calls vmalloc() should never get called. When we
: conveted jbd2_alloc() to suppor sub-page size allocations in commit
: d2eecb039368, there was an assumption that it could be called with a size
: greater than PAGE_SIZE, but that's certaily not true today.
Moreover vmalloc allocation might even lead to a deadlock because the
callers expect GFP_NOFS context while vmalloc is GFP_KERNEL.
2) __GFP_REPEAT for requests <= PAGE_ALLOC_COSTLY_ORDER is ignored
since the flag was introduced.
Let's simplify the code flow and use the slab allocator for sub-page
requests and the page allocator for others. Even though order > 0 is not
currently used as per above leave that option open.
Link: http://lkml.kernel.org/r/1464599699-30131-18-git-send-email-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/jbd2/journal.c | 32 +++++++-------------------------
1 file changed, 7 insertions(+), 25 deletions(-)
diff -puN fs/jbd2/journal.c~jbd2-get-rid-of-superfluous-__gfp_repeat fs/jbd2/journal.c
--- a/fs/jbd2/journal.c~jbd2-get-rid-of-superfluous-__gfp_repeat
+++ a/fs/jbd2/journal.c
@@ -2329,18 +2329,10 @@ void *jbd2_alloc(size_t size, gfp_t flag
BUG_ON(size & (size-1)); /* Must be a power of 2 */
- flags |= __GFP_REPEAT;
- if (size == PAGE_SIZE)
- ptr = (void *)__get_free_pages(flags, 0);
- else if (size > PAGE_SIZE) {
- int order = get_order(size);
-
- if (order < 3)
- ptr = (void *)__get_free_pages(flags, order);
- else
- ptr = vmalloc(size);
- } else
+ if (size < PAGE_SIZE)
ptr = kmem_cache_alloc(get_slab(size), flags);
+ else
+ ptr = (void *)__get_free_pages(flags, get_order(size));
/* Check alignment; SLUB has gotten this wrong in the past,
* and this can lead to user data corruption! */
@@ -2351,20 +2343,10 @@ void *jbd2_alloc(size_t size, gfp_t flag
void jbd2_free(void *ptr, size_t size)
{
- if (size == PAGE_SIZE) {
- free_pages((unsigned long)ptr, 0);
- return;
- }
- if (size > PAGE_SIZE) {
- int order = get_order(size);
-
- if (order < 3)
- free_pages((unsigned long)ptr, order);
- else
- vfree(ptr);
- return;
- }
- kmem_cache_free(get_slab(size), ptr);
+ if (size < PAGE_SIZE)
+ kmem_cache_free(get_slab(size), ptr);
+ else
+ free_pages((unsigned long)ptr, get_order(size));
};
/*
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
mm-oom_reaper-do-not-use-siglock-in-try_oom_reaper.patch
tree-wide-get-rid-of-__gfp_repeat-for-order-0-allocations-part-i.patch
x86-get-rid-of-superfluous-__gfp_repeat.patch
x86-efi-get-rid-of-superfluous-__gfp_repeat.patch
arm-get-rid-of-superfluous-__gfp_repeat.patch
arm64-get-rid-of-superfluous-__gfp_repeat.patch
arc-get-rid-of-superfluous-__gfp_repeat.patch
mips-get-rid-of-superfluous-__gfp_repeat.patch
nios2-get-rid-of-superfluous-__gfp_repeat.patch
parisc-get-rid-of-superfluous-__gfp_repeat.patch
score-get-rid-of-superfluous-__gfp_repeat.patch
powerpc-get-rid-of-superfluous-__gfp_repeat.patch
sparc-get-rid-of-superfluous-__gfp_repeat.patch
s390-get-rid-of-superfluous-__gfp_repeat.patch
sh-get-rid-of-superfluous-__gfp_repeat.patch
tile-get-rid-of-superfluous-__gfp_repeat.patch
unicore32-get-rid-of-superfluous-__gfp_repeat.patch
jbd2-get-rid-of-superfluous-__gfp_repeat.patch
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