Messages in this thread Patch in this message | | | From | Dave Kleikamp <> | Subject | [PATCH V8 07/33] iov_iter: ii_iovec_copy_to_user should pre-fault user pages | Date | Thu, 25 Jul 2013 12:50:33 -0500 |
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This duplicates the optimization in file_read_actor as a later patch will replace it with a call to __iov_iter_copy_to_user().
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> --- fs/iov-iter.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/fs/iov-iter.c b/fs/iov-iter.c index 6cb6be0..59f9556 100644 --- a/fs/iov-iter.c +++ b/fs/iov-iter.c @@ -80,17 +80,32 @@ static size_t ii_iovec_copy_to_user(struct page *page, return 0; } - kaddr = kmap(page); if (likely(i->nr_segs == 1)) { int left; char __user *buf = iov->iov_base + i->iov_offset; + /* + * Faults on the destination of a read are common, so do it + * before taking the kmap. + */ + if (!fault_in_pages_writeable(buf, bytes)) { + kaddr = kmap_atomic(page); + left = __copy_to_user_inatomic(buf, kaddr + offset, + bytes); + kunmap_atomic(kaddr); + if (left == 0) + goto success; + } + kaddr = kmap(page); left = copy_to_user(buf, kaddr + offset, bytes); + kunmap(page); +success: copied = bytes - left; } else { + kaddr = kmap(page); copied = __iovec_copy_to_user(kaddr + offset, iov, i->iov_offset, bytes, 0); + kunmap(page); } - kunmap(page); return copied; } -- 1.8.3.4
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