__NETDEV_ALLOC_SKB(9) Linux Networking __NETDEV_ALLOC_SKB(9)NAME
__netdev_alloc_skb - allocate an skbuff for rx on a specific device
SYNOPSIS
struct sk_buff * __netdev_alloc_skb(struct net_device * dev, unsigned int length, gfp_t gfp_mask);
ARGUMENTS
dev
network device to receive on
length
length to allocate
gfp_mask
get_free_pages mask, passed to alloc_skb
DESCRIPTION
Allocate a new sk_buff and assign it a usage count of one. The buffer has unspecified headroom built in. Users should allocate the headroom
they think they need without accounting for the built in space. The built in space is used for optimisations.
NULL is returned if there is no free memory.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 __NETDEV_ALLOC_SKB(9)
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BLK_MAKE_REQUEST(9) Block Devices BLK_MAKE_REQUEST(9)NAME
blk_make_request - given a bio, allocate a corresponding struct request.
SYNOPSIS
struct request * blk_make_request(struct request_queue * q, struct bio * bio, gfp_t gfp_mask);
ARGUMENTS
q
target request queue
bio
The bio describing the memory mappings that will be submitted for IO. It may be a chained-bio properly constructed by block/bio layer.
gfp_mask
gfp flags to be used for memory allocation
DESCRIPTION
blk_make_request is the parallel of generic_make_request for BLOCK_PC type commands. Where the struct request needs to be farther
initialized by the caller. It is passed a struct bio, which describes the memory info of the I/O transfer.
The caller of blk_make_request must make sure that bi_io_vec are set to describe the memory buffers. That bio_data_dir will return the
needed direction of the request. (And all bio's in the passed bio-chain are properly set accordingly)
If called under none-sleepable conditions, mapped bio buffers must not need bouncing, by calling the appropriate masked or flagged
allocator, suitable for the target device. Otherwise the call to blk_queue_bounce will BUG.
WARNING
When allocating/cloning a bio-chain, careful consideration should be given to how you allocate bios. In particular, you cannot use
__GFP_WAIT for anything but the first bio in the chain. Otherwise you risk waiting for IO completion of a bio that hasn't been submitted
yet, thus resulting in a deadlock. Alternatively bios should be allocated using bio_kmalloc instead of bio_alloc, as that avoids the
mempool deadlock. If possible a big IO should be split into smaller parts when allocation fails. Partial allocation should not be an error,
or you risk a live-lock.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 BLK_MAKE_REQUEST(9)