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authorLinus Torvalds <torvalds@linux-foundation.org>2021-09-17 19:23:44 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-17 19:23:44 +0300
commitddf21bd8ab984ccaa924f090fc7f515bb6d51414 (patch)
treef8c598a24317040feffff465a2f43eb326d65ee2 /lib
parent0bc7eb03cbd3e5d057cbe2ee15ddedf168f25a8d (diff)
parentb66ceaf324b394428bb47054140ddf03d8172e64 (diff)
downloadlinux-ddf21bd8ab984ccaa924f090fc7f515bb6d51414.tar.xz
Merge tag 'iov_iter.3-5.15-2021-09-17' of git://git.kernel.dk/linux-block
Pull io_uring iov_iter retry fixes from Jens Axboe: "This adds a helper to save/restore iov_iter state, and modifies io_uring to use it. After that is done, we can now kill the iter->truncated addition that we added for this release. The io_uring change is being overly cautious with the save/restore/advance, but better safe than sorry and we can always improve that and reduce the overhead if it proves to be of concern. The only case to be worried about in this regard is huge IO, where iteration can take a while to iterate segments. I spent some time writing test cases, and expanded the coverage quite a bit from the last posting of this. liburing carries this regression test case now: https://git.kernel.dk/cgit/liburing/tree/test/file-verify.c which exercises all of this. It now also supports provided buffers, and explicitly tests for end-of-file/device truncation as well. On top of that, Pavel sanitized the IOPOLL retry path to follow the exact same pattern as normal IO" * tag 'iov_iter.3-5.15-2021-09-17' of git://git.kernel.dk/linux-block: io_uring: move iopoll reissue into regular IO path Revert "iov_iter: track truncated size" io_uring: use iov_iter state save/restore helpers iov_iter: add helper to save iov_iter state
Diffstat (limited to 'lib')
-rw-r--r--lib/iov_iter.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index f2d50d69a6c3..755c10c5138c 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1972,3 +1972,39 @@ int import_single_range(int rw, void __user *buf, size_t len,
return 0;
}
EXPORT_SYMBOL(import_single_range);
+
+/**
+ * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
+ * iov_iter_save_state() was called.
+ *
+ * @i: &struct iov_iter to restore
+ * @state: state to restore from
+ *
+ * Used after iov_iter_save_state() to bring restore @i, if operations may
+ * have advanced it.
+ *
+ * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
+ */
+void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
+{
+ if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
+ !iov_iter_is_kvec(i))
+ return;
+ i->iov_offset = state->iov_offset;
+ i->count = state->count;
+ /*
+ * For the *vec iters, nr_segs + iov is constant - if we increment
+ * the vec, then we also decrement the nr_segs count. Hence we don't
+ * need to track both of these, just one is enough and we can deduct
+ * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
+ * size, so we can just increment the iov pointer as they are unionzed.
+ * ITER_BVEC _may_ be the same size on some archs, but on others it is
+ * not. Be safe and handle it separately.
+ */
+ BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
+ if (iov_iter_is_bvec(i))
+ i->bvec -= state->nr_segs - i->nr_segs;
+ else
+ i->iov -= state->nr_segs - i->nr_segs;
+ i->nr_segs = state->nr_segs;
+}