Re: [PATCH v2 4/4] mm: allow !GFP_KERNEL allocations for kvmalloc

[Uladzislau Rezki <urezki@gmail.com>]

On Mon, Nov 22, 2021 at 04:32:33PM +0100, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> A support for GFP_NO{FS,IO} and __GFP_NOFAIL has been implemented
> by previous patches so we can allow the support for kvmalloc. This
> will allow some external users to simplify or completely remove
> their helpers.
> 
> GFP_NOWAIT semantic hasn't been supported so far but it hasn't been
> explicitly documented so let's add a note about that.
> 
> ceph_kvmalloc is the first helper to be dropped and changed to
> kvmalloc.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
>  include/linux/ceph/libceph.h |  1 -
>  mm/util.c                    | 15 ++++-----------
>  net/ceph/buffer.c            |  4 ++--
>  net/ceph/ceph_common.c       | 27 ---------------------------
>  net/ceph/crypto.c            |  2 +-
>  net/ceph/messenger.c         |  2 +-
>  net/ceph/messenger_v2.c      |  2 +-
>  net/ceph/osdmap.c            | 12 ++++++------
>  8 files changed, 15 insertions(+), 50 deletions(-)
> 
> diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
> index 409d8c29bc4f..309acbcb5a8a 100644
> --- a/include/linux/ceph/libceph.h
> +++ b/include/linux/ceph/libceph.h
> @@ -295,7 +295,6 @@ extern bool libceph_compatible(void *data);
>  
>  extern const char *ceph_msg_type_name(int type);
>  extern int ceph_check_fsid(struct ceph_client *client, struct ceph_fsid *fsid);
> -extern void *ceph_kvmalloc(size_t size, gfp_t flags);
>  
>  struct fs_parameter;
>  struct fc_log;
> diff --git a/mm/util.c b/mm/util.c
> index e58151a61255..7275f2829e3f 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -549,13 +549,10 @@ EXPORT_SYMBOL(vm_mmap);
>   * Uses kmalloc to get the memory but if the allocation fails then falls back
>   * to the vmalloc allocator. Use kvfree for freeing the memory.
>   *
> - * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
> + * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
>   * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
>   * preferable to the vmalloc fallback, due to visible performance drawbacks.
>   *
> - * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
> - * fall back to vmalloc.
> - *
>   * Return: pointer to the allocated memory of %NULL in case of failure
>   */
>  void *kvmalloc_node(size_t size, gfp_t flags, int node)
> @@ -563,13 +560,6 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
>  	gfp_t kmalloc_flags = flags;
>  	void *ret;
>  
> -	/*
> -	 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
> -	 * so the given set of flags has to be compatible.
> -	 */
> -	if ((flags & GFP_KERNEL) != GFP_KERNEL)
> -		return kmalloc_node(size, flags, node);
> -
>  	/*
>  	 * We want to attempt a large physically contiguous block first because
>  	 * it is less likely to fragment multiple larger blocks and therefore
> @@ -582,6 +572,9 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
>  
>  		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
>  			kmalloc_flags |= __GFP_NORETRY;
> +
> +		/* nofail semantic is implemented by the vmalloc fallback */
> +		kmalloc_flags &= ~__GFP_NOFAIL;
>  	}
>  
>  	ret = kmalloc_node(size, kmalloc_flags, node);
> diff --git a/net/ceph/buffer.c b/net/ceph/buffer.c
> index 5622763ad402..7e51f128045d 100644
> --- a/net/ceph/buffer.c
> +++ b/net/ceph/buffer.c
> @@ -7,7 +7,7 @@
>  
>  #include <linux/ceph/buffer.h>
>  #include <linux/ceph/decode.h>
> -#include <linux/ceph/libceph.h> /* for ceph_kvmalloc */
> +#include <linux/ceph/libceph.h> /* for kvmalloc */
>  
>  struct ceph_buffer *ceph_buffer_new(size_t len, gfp_t gfp)
>  {
> @@ -17,7 +17,7 @@ struct ceph_buffer *ceph_buffer_new(size_t len, gfp_t gfp)
>  	if (!b)
>  		return NULL;
>  
> -	b->vec.iov_base = ceph_kvmalloc(len, gfp);
> +	b->vec.iov_base = kvmalloc(len, gfp);
>  	if (!b->vec.iov_base) {
>  		kfree(b);
>  		return NULL;
> diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> index 97d6ea763e32..9441b4a4912b 100644
> --- a/net/ceph/ceph_common.c
> +++ b/net/ceph/ceph_common.c
> @@ -190,33 +190,6 @@ int ceph_compare_options(struct ceph_options *new_opt,
>  }
>  EXPORT_SYMBOL(ceph_compare_options);
>  
> -/*
> - * kvmalloc() doesn't fall back to the vmalloc allocator unless flags are
> - * compatible with (a superset of) GFP_KERNEL.  This is because while the
> - * actual pages are allocated with the specified flags, the page table pages
> - * are always allocated with GFP_KERNEL.
> - *
> - * ceph_kvmalloc() may be called with GFP_KERNEL, GFP_NOFS or GFP_NOIO.
> - */
> -void *ceph_kvmalloc(size_t size, gfp_t flags)
> -{
> -	void *p;
> -
> -	if ((flags & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS)) {
> -		p = kvmalloc(size, flags);
> -	} else if ((flags & (__GFP_IO | __GFP_FS)) == __GFP_IO) {
> -		unsigned int nofs_flag = memalloc_nofs_save();
> -		p = kvmalloc(size, GFP_KERNEL);
> -		memalloc_nofs_restore(nofs_flag);
> -	} else {
> -		unsigned int noio_flag = memalloc_noio_save();
> -		p = kvmalloc(size, GFP_KERNEL);
> -		memalloc_noio_restore(noio_flag);
> -	}
> -
> -	return p;
> -}
> -
>  static int parse_fsid(const char *str, struct ceph_fsid *fsid)
>  {
>  	int i = 0;
> diff --git a/net/ceph/crypto.c b/net/ceph/crypto.c
> index 92d89b331645..051d22c0e4ad 100644
> --- a/net/ceph/crypto.c
> +++ b/net/ceph/crypto.c
> @@ -147,7 +147,7 @@ void ceph_crypto_key_destroy(struct ceph_crypto_key *key)
>  static const u8 *aes_iv = (u8 *)CEPH_AES_IV;
>  
>  /*
> - * Should be used for buffers allocated with ceph_kvmalloc().
> + * Should be used for buffers allocated with kvmalloc().
>   * Currently these are encrypt out-buffer (ceph_buffer) and decrypt
>   * in-buffer (msg front).
>   *
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 57d043b382ed..7b891be799d2 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -1920,7 +1920,7 @@ struct ceph_msg *ceph_msg_new2(int type, int front_len, int max_data_items,
>  
>  	/* front */
>  	if (front_len) {
> -		m->front.iov_base = ceph_kvmalloc(front_len, flags);
> +		m->front.iov_base = kvmalloc(front_len, flags);
>  		if (m->front.iov_base == NULL) {
>  			dout("ceph_msg_new can't allocate %d bytes\n",
>  			     front_len);
> diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
> index cc40ce4e02fb..c4099b641b38 100644
> --- a/net/ceph/messenger_v2.c
> +++ b/net/ceph/messenger_v2.c
> @@ -308,7 +308,7 @@ static void *alloc_conn_buf(struct ceph_connection *con, int len)
>  	if (WARN_ON(con->v2.conn_buf_cnt >= ARRAY_SIZE(con->v2.conn_bufs)))
>  		return NULL;
>  
> -	buf = ceph_kvmalloc(len, GFP_NOIO);
> +	buf = kvmalloc(len, GFP_NOIO);
>  	if (!buf)
>  		return NULL;
>  
> diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
> index 75b738083523..2823bb3cff55 100644
> --- a/net/ceph/osdmap.c
> +++ b/net/ceph/osdmap.c
> @@ -980,7 +980,7 @@ static struct crush_work *alloc_workspace(const struct crush_map *c)
>  	work_size = crush_work_size(c, CEPH_PG_MAX_SIZE);
>  	dout("%s work_size %zu bytes\n", __func__, work_size);
>  
> -	work = ceph_kvmalloc(work_size, GFP_NOIO);
> +	work = kvmalloc(work_size, GFP_NOIO);
>  	if (!work)
>  		return NULL;
>  
> @@ -1190,9 +1190,9 @@ static int osdmap_set_max_osd(struct ceph_osdmap *map, u32 max)
>  	if (max == map->max_osd)
>  		return 0;
>  
> -	state = ceph_kvmalloc(array_size(max, sizeof(*state)), GFP_NOFS);
> -	weight = ceph_kvmalloc(array_size(max, sizeof(*weight)), GFP_NOFS);
> -	addr = ceph_kvmalloc(array_size(max, sizeof(*addr)), GFP_NOFS);
> +	state = kvmalloc(array_size(max, sizeof(*state)), GFP_NOFS);
> +	weight = kvmalloc(array_size(max, sizeof(*weight)), GFP_NOFS);
> +	addr = kvmalloc(array_size(max, sizeof(*addr)), GFP_NOFS);
>  	if (!state || !weight || !addr) {
>  		kvfree(state);
>  		kvfree(weight);
> @@ -1222,7 +1222,7 @@ static int osdmap_set_max_osd(struct ceph_osdmap *map, u32 max)
>  	if (map->osd_primary_affinity) {
>  		u32 *affinity;
>  
> -		affinity = ceph_kvmalloc(array_size(max, sizeof(*affinity)),
> +		affinity = kvmalloc(array_size(max, sizeof(*affinity)),
>  					 GFP_NOFS);
>  		if (!affinity)
>  			return -ENOMEM;
> @@ -1503,7 +1503,7 @@ static int set_primary_affinity(struct ceph_osdmap *map, int osd, u32 aff)
>  	if (!map->osd_primary_affinity) {
>  		int i;
>  
> -		map->osd_primary_affinity = ceph_kvmalloc(
> +		map->osd_primary_affinity = kvmalloc(
>  		    array_size(map->max_osd, sizeof(*map->osd_primary_affinity)),
>  		    GFP_NOFS);
>  		if (!map->osd_primary_affinity)
> -- 
> 2.30.2
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki