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authorAleix Roca Nonell <aleix.rocanonell@bsc.es>2019-08-15 14:03:22 +0200
committerJens Axboe <axboe@kernel.dk>2019-08-15 11:03:38 -0600
commit99c79f6692ccdc42e04deea8a36e22bb48168a62 (patch)
treed665a31392cb938848e7a17e21d7fe2b034ed862
parentae78ca3cf3d9e9f914bfcd0bc5c389ff18b9c2e0 (diff)
downloadlinux-99c79f6692ccdc42e04deea8a36e22bb48168a62.tar.bz2
io_uring: fix manual setup of iov_iter for fixed buffers
Commit bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") introduced an optimization to avoid using the slow iov_iter_advance by manually populating the iov_iter iterator in some cases. However, the computation of the iterator count field was erroneous: The first bvec was always accounted for an extent of page size even if the bvec length was smaller. In consequence, some I/O operations on fixed buffers were unable to operate on the full extent of the buffer, consistently skipping some bytes at the end of it. Fixes: bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") Cc: stable@vger.kernel.org Signed-off-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/io_uring.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d542f1cf4428..aa25b5bbd4ae 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1097,10 +1097,8 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
iter->bvec = bvec + seg_skip;
iter->nr_segs -= seg_skip;
- iter->count -= (seg_skip << PAGE_SHIFT);
+ iter->count -= bvec->bv_len + offset;
iter->iov_offset = offset & ~PAGE_MASK;
- if (iter->iov_offset)
- iter->count -= iter->iov_offset;
}
}