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SubjectRe: [PATCH 07/12] staging: lustre: libcfs: simplify memory allocation.
On Wed, Dec 13 2017, NeilBrown wrote:

> 1/ Use kvmalloc() instead of kmalloc or vmalloc
> 2/ Discard the _GFP() interfaces that are never used.
> We only ever do GFP_NOFS and GFP_ATOMIC allocations,
> so support each of those explicitly.

Hi,
I just remembered that posting this patch was, maybe, a little premature.
vmalloc() doesn't support GFP_NOFS, so kvmalloc() warns about an attempt
to use GFP_NOFS.
lustre potentially used vmalloc in GFP_NOFS context, and so now calls
kvmalloc() with GFP_NOFS, which triggers a warning.

I haven't yet looking into how to remove the warning. Maybe all
GFP_NOFS usages should use kmalloc(), not kvmalloc(), and accept the
increased chance of failure.
I'll dig deeper and hope to have a clearer opinion soon.

As it is only a warning, it is probably OK to keep the patch in
staging-next, but I wouldn't object if it was dropped.

Thanks,
NeilBrown



>
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
> .../lustre/include/linux/libcfs/libcfs_private.h | 42 ++++++--------------
> 1 file changed, 12 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> index 2f4ff595fac9..c874f9d15c72 100644
> --- a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> +++ b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> @@ -84,14 +84,6 @@ do { \
> lbug_with_loc(&msgdata); \
> } while (0)
>
> -#ifndef LIBCFS_VMALLOC_SIZE
> -#define LIBCFS_VMALLOC_SIZE (2 << PAGE_SHIFT) /* 2 pages */
> -#endif
> -
> -#define LIBCFS_ALLOC_PRE(size, mask) \
> - LASSERT(!in_interrupt() || ((size) <= LIBCFS_VMALLOC_SIZE && \
> - !gfpflags_allow_blocking(mask)))
> -
> #define LIBCFS_ALLOC_POST(ptr, size) \
> do { \
> if (unlikely(!(ptr))) { \
> @@ -103,46 +95,36 @@ do { \
> } while (0)
>
> /**
> - * allocate memory with GFP flags @mask
> + * default allocator
> */
> -#define LIBCFS_ALLOC_GFP(ptr, size, mask) \
> +#define LIBCFS_ALLOC(ptr, size) \
> do { \
> - LIBCFS_ALLOC_PRE((size), (mask)); \
> - (ptr) = (size) <= LIBCFS_VMALLOC_SIZE ? \
> - kmalloc((size), (mask)) : vmalloc(size); \
> + LASSERT(!in_interrupt()); \
> + (ptr) = kvmalloc((size), GFP_NOFS); \
> LIBCFS_ALLOC_POST((ptr), (size)); \
> } while (0)
>
> -/**
> - * default allocator
> - */
> -#define LIBCFS_ALLOC(ptr, size) \
> - LIBCFS_ALLOC_GFP(ptr, size, GFP_NOFS)
> -
> /**
> * non-sleeping allocator
> */
> -#define LIBCFS_ALLOC_ATOMIC(ptr, size) \
> - LIBCFS_ALLOC_GFP(ptr, size, GFP_ATOMIC)
> +#define LIBCFS_ALLOC_ATOMIC(ptr, size) \
> +do { \
> + (ptr) = kmalloc((size), GFP_ATOMIC); \
> + LIBCFS_ALLOC_POST(ptr, size); \
> +} while (0)
>
> /**
> * allocate memory for specified CPU partition
> * \a cptab != NULL, \a cpt is CPU partition id of \a cptab
> * \a cptab == NULL, \a cpt is HW NUMA node id
> */
> -#define LIBCFS_CPT_ALLOC_GFP(ptr, cptab, cpt, size, mask) \
> +#define LIBCFS_CPT_ALLOC(ptr, cptab, cpt, size) \
> do { \
> - LIBCFS_ALLOC_PRE((size), (mask)); \
> - (ptr) = (size) <= LIBCFS_VMALLOC_SIZE ? \
> - kmalloc_node((size), (mask), cfs_cpt_spread_node(cptab, cpt)) :\
> - vmalloc_node(size, cfs_cpt_spread_node(cptab, cpt)); \
> + LASSERT(!in_interrupt()); \
> + (ptr) = kvmalloc_node((size), GFP_NOFS, cfs_cpt_spread_node(cptab, cpt)); \
> LIBCFS_ALLOC_POST((ptr), (size)); \
> } while (0)
>
> -/** default numa allocator */
> -#define LIBCFS_CPT_ALLOC(ptr, cptab, cpt, size) \
> - LIBCFS_CPT_ALLOC_GFP(ptr, cptab, cpt, size, GFP_NOFS)
> -
> #define LIBCFS_FREE(ptr, size) \
> do { \
> if (unlikely(!(ptr))) { \
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