On 11/21/2014 04:08 AM, Omar Sandoval wrote:
> Reads through the iov_iter infrastructure for kernel pages shouldn't be
> dirtied
> by the direct I/O code.
>
> This is based on Dave Kleikamp's and Ming Lei's previously posted patches.
Acked-by: Dave Kleikamp <dave.kleik...@oracle.com>
> Cc: Ming Lei <ming....@canonical.com>
> Signed-off-by: Omar Sandoval <osan...@osandov.com>
> ---
> fs/direct-io.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index e181b6b..e542ce4 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -120,6 +120,7 @@ struct dio {
> spinlock_t bio_lock; /* protects BIO fields below */
> int page_errors; /* errno from get_user_pages() */
> int is_async; /* is IO async ? */
> + int should_dirty; /* should we mark read pages dirty? */
> bool defer_completion; /* defer AIO completion to workqueue? */
> int io_error; /* IO error in completion path */
> unsigned long refcount; /* direct_io_worker() and bios */
> @@ -392,7 +393,7 @@ static inline void dio_bio_submit(struct dio *dio, struct
> dio_submit *sdio)
> dio->refcount++;
> spin_unlock_irqrestore(&dio->bio_lock, flags);
>
> - if (dio->is_async && dio->rw == READ)
> + if (dio->is_async && dio->rw == READ && dio->should_dirty)
> bio_set_pages_dirty(bio);
>
> if (sdio->submit_io)
> @@ -463,13 +464,13 @@ static int dio_bio_complete(struct dio *dio, struct bio
> *bio)
> if (!uptodate)
> dio->io_error = -EIO;
>
> - if (dio->is_async && dio->rw == READ) {
> + if (dio->is_async && dio->rw == READ && dio->should_dirty) {
> bio_check_pages_dirty(bio); /* transfers ownership */
> } else {
> bio_for_each_segment_all(bvec, bio, i) {
> struct page *page = bvec->bv_page;
>
> - if (dio->rw == READ && !PageCompound(page))
> + if (dio->rw == READ && !PageCompound(page) &&
> dio->should_dirty)
> set_page_dirty_lock(page);
> page_cache_release(page);
> }
> @@ -1177,6 +1178,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb,
> struct inode *inode,
>
> dio->inode = inode;
> dio->rw = rw;
> + dio->should_dirty = !(iter->type & ITER_BVEC);
>
> /*
> * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
>
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