Re: [PATCH v16 02/15] iov_iter: Add a segmented queue of bio_vec[]

[sashiko-bot@kernel.org]

> Add the concept of a segmented queue of bio_vec[] arrays.  This allows an
> indefinite quantity of elements to be handled and allows things like
> network filesystems and crypto drivers to glue bits on the ends without
> having to reallocate the array.
> 
> The bvecq struct that defines each segment also carries capacity/usage
> information along with flags indicating whether the constituent memory
> regions need freeing or unpinning.  The bvecq structs are refcounted to
> allow a queue to be extracted in batches and split between a number of
> subrequests.
> 
> The bvecq can have the bio_vec[] it manages allocated in with it, but this
> is not required.  A flag is provided for if this is the case as comparing
> ->bv to ->__bv is not sufficient to detect this case.
> 
> Add an iterator type ITER_BVECQ for it.  This is intended to replace
> ITER_FOLIOQ (and ITER_XARRAY).
> 
> Note that the prev pointer is only really needed for iov_iter_revert() and
> could be dispensed with if struct iov_iter contained the head information
> as well as the current point.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>

Sashiko has reviewed this patch and found no issues.

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