优化一下下面这个函数 static u64 read_one_extent(struct zram *zram, u32 eid, u16 gid) { struct erdio *erdio = NULL; u32 ext_size = 0; int ret; struct erdio_priv *priv = NULL; priv = kmalloc(sizeof(struct erdio_priv), GFP_NOIO); if (!priv) goto err; priv->gid = gid; priv->zram = zram; erdio = extramdisk_io_get(eid, GFP_NOIO, REQ_OP_READ); if (!erdio) goto err; ext_size = extramdisk_extent_size(eid); ret = extramdisk_read_async(erdio, read_endio, priv); if (ret) goto err; return ext_size; err: extramdisk_io_put(erdio); kfree(priv); return 0; }

可以尝试以下优化：

1. 将 kmalloc() 和 kfree() 改为使用栈分配和动态分配：

static u64 read_one_extent(struct zram *zram, u32 eid, u16 gid) {
    struct erdio *erdio = NULL;
    u32 ext_size = 0;
    int ret;
    struct erdio_priv priv = {
        .gid = gid,
        .zram = zram,
    };

    erdio = extramdisk_io_get(eid, GFP_NOIO, REQ_OP_READ);
    if (!erdio)
        return 0;

    ext_size = extramdisk_extent_size(eid);
    ret = extramdisk_read_async(erdio, read_endio, &priv);
    if (ret) {
        extramdisk_io_put(erdio);
        return 0;
    }

    extramdisk_io_put(erdio);
    return ext_size;
}

2. 可以考虑使用 static inline 函数，这样可以避免函数调用的开销：

static inline struct erdio_priv *allocate_erdio_priv(u16 gid, struct zram *zram) {
    struct erdio_priv *priv = kmalloc(sizeof(struct erdio_priv), GFP_NOIO);
    if (!priv)
        return NULL;

    priv->gid = gid;
    priv->zram = zram;
    return priv;
}

static u64 read_one_extent(struct zram *zram, u32 eid, u16 gid) {
    struct erdio *erdio = NULL;
    u32 ext_size = 0;
    int ret;
    struct erdio_priv *priv = allocate_erdio_priv(gid, zram);

    if (!priv)
        return 0;

    erdio = extramdisk_io_get(eid, GFP_NOIO, REQ_OP_READ);
    if (!erdio) {
        kfree(priv);
        return 0;
    }

    ext_size = extramdisk_extent_size(eid);
    ret = extramdisk_read_async(erdio, read_endio, priv);
    if (ret) {
        extramdisk_io_put(erdio);
        kfree(priv);
        return 0;
    }

    extramdisk_io_put(erdio);
    return ext_size;
}

3. 可以考虑使用 GOTO 语句的替代方案，例如使用 if-else：

static inline struct erdio_priv *allocate_erdio_priv(u16 gid, struct zram *zram) {
    struct erdio_priv *priv = kmalloc(sizeof(struct erdio_priv), GFP_NOIO);
    if (!priv)
        return NULL;

    priv->gid = gid;
    priv->zram = zram;
    return priv;
}

static u64 read_one_extent(struct zram *zram, u32 eid, u16 gid) {
    struct erdio *erdio = NULL;
    u32 ext_size = 0;
    int ret;
    struct erdio_priv *priv = allocate_erdio_priv(gid, zram);

    if (!priv)
        return 0;

    erdio = extramdisk_io_get(eid, GFP_NOIO, REQ_OP_READ);
    if (erdio) {
        ext_size = extramdisk_extent_size(eid);
        ret = extramdisk_read_async(erdio, read_endio, priv);
        if (!ret) {
            extramdisk_io_put(erdio);
            return ext_size;
        }
        extramdisk_io_put(erdio);
    }

    kfree(priv);
    return 0;
}