Re: [PATCH] xfs: allocate sector sized IO buffer via page_frag_alloc

[Christopher Lameter]

On Tue, 26 Feb 2019, Ming Lei wrote:

> Then something like the following patch should work for all fs, could
> anyone comment on this approach?

Note that various subsystems have similar implementations. Have a look at

drivers/dma/dmaengine.c

struct dmaengine_unmap_pool {
        struct kmem_cache *cache;
        const char *name;
        mempool_t *pool;
        size_t size;
};

#define __UNMAP_POOL(x) { .size = x, .name = "dmaengine-unmap-"
__stringify(x) }
static struct dmaengine_unmap_pool unmap_pool[] = {
        __UNMAP_POOL(2),
        #if IS_ENABLED(CONFIG_DMA_ENGINE_RAID)
        __UNMAP_POOL(16),
        __UNMAP_POOL(128),
        __UNMAP_POOL(256),
        #endif
};

Or drivers/md/dm-bufio.c:

struct dm_bufio_client {
        struct mutex lock;

        struct list_head lru[LIST_SIZE];
        unsigned long n_buffers[LIST_SIZE];

        struct block_device *bdev;
        unsigned block_size;
        s8 sectors_per_block_bits;
        void (*alloc_callback)(struct dm_buffer *);
        void (*write_callback)(struct dm_buffer *);

        struct kmem_cache *slab_buffer;
        struct kmem_cache *slab_cache;
        struct dm_io_client *dm_io;

        struct list_head reserved_buffers;
        unsigned need_reserved_buffers;

        unsigned minimum_buffers;

        struct rb_root buffer_tree;
        wait_queue_head_t free_buffer_wait;

        sector_t start;

        int async_write_error;

        struct list_head client_list;
        struct shrinker shrinker;
};