This patch fixes two bugs in sglist(9) and improves robustness of the API via

better semantics if a request to append an address range to an existing list
fails.
- When cloning an sglist, properly set the length in the new sglist instead of
  leaving the new list empty.
- Properly compute the amount of data added to an sglist via
  _sglist_append_buf().  This allows sglist_consume_uio() to properly update
  uio_resid.
- When a request to append an address range to a scatter/gather list fails,
  restore the sglist to the state it had at the start of the function call
  instead of resetting it to an empty list.

Requested by:	np (3)
Approved by:	re (kib)

1 files changed, 4 insertions, 0 deletions

diff --git a/share/man/man9/sglist.9 b/share/man/man9/sglist.9
index a265498..e43a04b 100644
--- a/share/man/man9/sglist.9
+++ b/share/man/man9/sglist.9
@@ -191,6 +191,8 @@ Specifically, the
 family of routines can be used to append the physical address ranges described
 by an object to the end of a scatter/gather list.
 All of these routines return 0 on success or an error on failure.
+If a request to append an address range to a scatter/gather list fails,
+the scatter/gather list will remain unchanged.
 .Pp
 The
 .Nm sglist_append
@@ -445,6 +447,7 @@ There are not enough available segments in the scatter/gather list
 to append the physical address ranges from
 .Fa second .
 .El
+.Pp
 The
 .Nm sglist_slice
 function returns the following errors on failure:
@@ -470,6 +473,7 @@ list in
 .Fa *slice
 to describe the requested physical address ranges.
 .El
+.Pp
 The
 .Nm sglist_split
 function returns the following errors on failure: