K 10
svn:author
V 7
asomers
K 8
svn:date
V 27
2020-09-11T20:49:36.565840Z
K 7
svn:log
V 413
cp: fall back to read/write if copy_file_range fails

Even though copy_file_range has a file-system agnostic version, it still
fails on devfs (perhaps because the file descriptor is non-seekable?) In
that case, fallback to old-fashioned read/write. Fixes
"cp /dev/null /tmp/null"

PR:		249248
Reported by:	Michael Butler
Reviewed by:	mjg
MFC-With:	365549
Differential Revision:	https://reviews.freebsd.org/D26395

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