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authorDarrick J. Wong <darrick.wong@oracle.com>2018-12-02 08:38:07 -0800
committerDarrick J. Wong <darrick.wong@oracle.com>2018-12-04 09:40:02 -0800
commit8f67b5adc030553fbc877124306f3f3bdab89aa8 (patch)
parent17614445576b6af24e9cf36607c6448164719c96 (diff)
iomap: partially revert 4721a601099 (simulated directio short read on EFAULT)
In commit 4721a601099, we tried to fix a problem wherein directio reads into a splice pipe will bounce EFAULT/EAGAIN all the way out to userspace by simulating a zero-byte short read. This happens because some directio read implementations (xfs) will call bio_iov_iter_get_pages to grab pipe buffer pages and issue asynchronous reads, but as soon as we run out of pipe buffers that _get_pages call returns EFAULT, which the splice code translates to EAGAIN and bounces out to userspace. In that commit, the iomap code catches the EFAULT and simulates a zero-byte read, but that causes assertion errors on regular splice reads because xfs doesn't allow short directio reads. This causes infinite splice() loops and assertion failures on generic/095 on overlayfs because xfs only permit total success or total failure of a directio operation. The underlying issue in the pipe splice code has now been fixed by changing the pipe splice loop to avoid avoid reading more data than there is space in the pipe. Therefore, it's no longer necessary to simulate the short directio, so remove the hack from iomap. Fixes: 4721a601099 ("iomap: dio data corruption and spurious errors when pipes fill") Reported-by: Murphy Zhou <jencce.kernel@gmail.com> Ranted-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
1 files changed, 0 insertions, 9 deletions
diff --git a/fs/iomap.c b/fs/iomap.c
index 3ffb776fbebe..d6bc98ae8d35 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1877,15 +1877,6 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->wait_for_completion = true;
ret = 0;
- /*
- * Splicing to pipes can fail on a full pipe. We have to
- * swallow this to make it look like a short IO
- * otherwise the higher splice layers will completely
- * mishandle the error and stop moving data.
- */
- if (ret == -EFAULT)
- ret = 0;
pos += ret;