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netfs: Add support for DIO buffering

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Add a bvec array pointer and an iterator to netfs_io_request for either
holding a copy of a DIO iterator or a list of all the bits of buffer
pointed to by a DIO iterator.

There are two problems:  Firstly, if an iovec-class iov_iter is passed to
->read_iter() or ->write_iter(), this cannot be passed directly to
kernel_sendmsg() or kernel_recvmsg() as that may cause locking recursion if
a fault is generated, so we need to keep track of the pages involved
separately.

Secondly, if the I/O is asynchronous, we must copy the iov_iter describing
the buffer before returning to the caller as it may be immediately
deallocated.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
This commit is contained in:
David Howells
2021-07-09 08:41:17 +01:00
parent 92b6cc5d1e
commit 21d706d5cf
2 changed files with 13 additions and 0 deletions
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10
fs/netfs/objects.c
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@@ -76,6 +76,7 @@ static void netfs_free_request(struct work_struct *work)
{
struct netfs_io_request *rreq =
container_of(work, struct netfs_io_request, work);
unsigned int i;
trace_netfs_rreq(rreq, netfs_rreq_trace_free);
netfs_proc_del_rreq(rreq);
@@ -84,6 +85,15 @@ static void netfs_free_request(struct work_struct *work)
rreq->netfs_ops->free_request(rreq);
if (rreq->cache_resources.ops)
rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
if (rreq->direct_bv) {
for (i = 0; i < rreq->direct_bv_count; i++) {
if (rreq->direct_bv[i].bv_page) {
if (rreq->direct_bv_unpin)
unpin_user_page(rreq->direct_bv[i].bv_page);
}
}
kvfree(rreq->direct_bv);
}
kfree_rcu(rreq, rcu);
netfs_stat_d(&netfs_n_rh_rreq);
}