From 9b2e0016d04c6542ace0128eb82ecb3b10c97e43 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Sat, 9 Jan 2021 16:02:58 +0000 Subject: [PATCH] bvec/iter: disallow zero-length segment bvecs zero-length bvec segments are allowed in general, but not handled by bio and down the block layer so filtered out. This inconsistency may be confusing and prevent from optimisations. As zero-length segments are useless and places that were generating them are patched, declare them not allowed. Reviewed-by: Christoph Hellwig Signed-off-by: Pavel Begunkov Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- Documentation/block/biovecs.rst | 2 ++ Documentation/filesystems/porting.rst | 7 +++++++ lib/iov_iter.c | 2 -- 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/Documentation/block/biovecs.rst b/Documentation/block/biovecs.rst index 36771a131b56..ddb867e0185b 100644 --- a/Documentation/block/biovecs.rst +++ b/Documentation/block/biovecs.rst @@ -40,6 +40,8 @@ normal code doesn't have to deal with bi_bvec_done. There is a lower level advance function - bvec_iter_advance() - which takes a pointer to a biovec, not a bio; this is used by the bio integrity code. +As of 5.12 bvec segments with zero bv_len are not supported. + What's all this get us? ======================= diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 867036aa90b8..c722d94f29ea 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -865,3 +865,10 @@ no matter what. Everything is handled by the caller. clone_private_mount() returns a longterm mount now, so the proper destructor of its result is kern_unmount() or kern_unmount_array(). + +--- + +**mandatory** + +zero-length bvec segments are disallowed, they must be filtered out before +passed on to an iterator. diff --git a/lib/iov_iter.c b/lib/iov_iter.c index a21e6a5792c5..6c597cdfcf5b 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -72,8 +72,6 @@ __start.bi_bvec_done = skip; \ __start.bi_idx = 0; \ for_each_bvec(__v, i->bvec, __bi, __start) { \ - if (!__v.bv_len) \ - continue; \ (void)(STEP); \ } \ }