From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: Dave Jones <davej@codemonkey.org.uk>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
linux-xfs@vger.kernel.org
Subject: Re: iov_iter_pipe warning.
Date: Mon, 11 Sep 2017 21:17:09 +0100 [thread overview]
Message-ID: <20170911201709.GL5426@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170911200713.GK5426@ZenIV.linux.org.uk>
On Mon, Sep 11, 2017 at 09:07:13PM +0100, Al Viro wrote:
> Strictly speaking that behaviour doesn't violate POSIX. It is, however,
> atrocious from the QoI standpoint, and for no good reason whatsoever.
> It's quite easy to do better, and doing so would've eliminated the problems
> in pipe-backed case as well (see below). In addition to that, I would
> consider teaching bio_iov_iter_get_pages() to take the maximal bio size
> as an explict argument. That would've killed the need of copying the
> iterator and calling iov_iter_advance() in iomap_dio_actor() at all.
> Anyway, the minimal candidate fix follows; it won't do anything about
> the WARN_ON() in there, seeing that those are deliberate "program is
> doing something bogus" things, but it should eliminate all crap with
> ->splice_read() misreporting the amount of data it has copied.
... and after minimal testing and fixing a braino in "found an IO error"
case, that's
diff --git a/fs/iomap.c b/fs/iomap.c
index 269b24a01f32..012e1f247e13 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -832,6 +832,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
struct bio *bio;
bool need_zeroout = false;
int nr_pages, ret;
+ size_t copied = 0;
if ((pos | length | align) & ((1 << blkbits) - 1))
return -EINVAL;
@@ -843,7 +844,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
/*FALLTHRU*/
case IOMAP_UNWRITTEN:
if (!(dio->flags & IOMAP_DIO_WRITE)) {
- iov_iter_zero(length, dio->submit.iter);
+ length = iov_iter_zero(length, dio->submit.iter);
dio->size += length;
return length;
}
@@ -880,8 +881,11 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
}
do {
- if (dio->error)
+ size_t n;
+ if (dio->error) {
+ iov_iter_revert(dio->submit.iter, copied);
return 0;
+ }
bio = bio_alloc(GFP_KERNEL, nr_pages);
bio_set_dev(bio, iomap->bdev);
@@ -894,20 +898,24 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
ret = bio_iov_iter_get_pages(bio, &iter);
if (unlikely(ret)) {
bio_put(bio);
- return ret;
+ return copied ? copied : ret;
}
+ n = bio->bi_iter.bi_size;
if (dio->flags & IOMAP_DIO_WRITE) {
bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
- task_io_account_write(bio->bi_iter.bi_size);
+ task_io_account_write(n);
} else {
bio_set_op_attrs(bio, REQ_OP_READ, 0);
if (dio->flags & IOMAP_DIO_DIRTY)
bio_set_pages_dirty(bio);
}
- dio->size += bio->bi_iter.bi_size;
- pos += bio->bi_iter.bi_size;
+ iov_iter_advance(dio->submit.iter, n);
+
+ dio->size += n;
+ pos += n;
+ copied += n;
nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
@@ -923,9 +931,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
if (pad)
iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
}
-
- iov_iter_advance(dio->submit.iter, length);
- return length;
+ return copied;
}
ssize_t
next prev parent reply other threads:[~2017-09-11 20:17 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-21 20:59 iov_iter_pipe warning Dave Jones
2017-04-05 22:02 ` Dave Jones
2017-04-10 19:28 ` Al Viro
2017-04-10 19:42 ` Dave Jones
2017-04-10 19:57 ` Al Viro
2017-04-10 23:48 ` Dave Jones
2017-04-11 0:22 ` Al Viro
2017-04-11 3:05 ` Dave Jones
2017-04-11 3:28 ` Al Viro
2017-04-11 20:53 ` Dave Jones
2017-04-11 21:12 ` Al Viro
2017-04-11 22:25 ` Dave Jones
2017-04-11 23:28 ` Al Viro
2017-04-11 23:34 ` Dave Jones
2017-04-11 23:48 ` Al Viro
2017-04-11 23:45 ` Dave Jones
2017-04-11 23:51 ` Al Viro
2017-04-11 23:56 ` Al Viro
2017-04-12 0:06 ` Dave Jones
2017-04-12 0:17 ` Al Viro
2017-04-12 0:58 ` Dave Jones
2017-04-12 1:15 ` Al Viro
2017-04-12 2:29 ` Dave Jones
2017-04-12 2:58 ` Al Viro
2017-04-12 14:35 ` Dave Jones
2017-04-12 15:26 ` Al Viro
2017-04-12 16:27 ` Dave Jones
2017-04-12 17:07 ` Al Viro
2017-04-12 19:03 ` Dave Jones
2017-04-21 17:54 ` Al Viro
2017-04-27 4:19 ` Dave Jones
2017-04-27 16:34 ` Dave Jones
2017-04-27 17:39 ` Al Viro
2017-04-28 15:29 ` Dave Jones
2017-04-28 16:43 ` Al Viro
2017-04-28 16:50 ` Dave Jones
2017-04-28 17:20 ` Al Viro
2017-04-28 18:25 ` Al Viro
2017-04-29 1:58 ` Dave Jones
2017-04-29 2:47 ` Al Viro
2017-04-29 15:51 ` Dave Jones
2017-04-29 20:46 ` [git pull] vfs.git fix (Re: iov_iter_pipe warning.) Al Viro
2017-08-07 20:18 ` iov_iter_pipe warning Dave Jones
2017-08-28 20:31 ` Dave Jones
2017-08-29 4:25 ` Darrick J. Wong
2017-08-30 17:05 ` Dave Jones
2017-08-30 17:13 ` Darrick J. Wong
2017-08-30 17:17 ` Dave Jones
2017-09-06 20:03 ` Dave Jones
2017-09-06 23:46 ` Dave Chinner
2017-09-07 3:48 ` Dave Jones
2017-09-07 4:33 ` Al Viro
2017-09-08 1:04 ` Al Viro
2017-09-10 1:07 ` Dave Jones
2017-09-10 2:57 ` Al Viro
2017-09-10 16:07 ` Dave Jones
2017-09-10 20:05 ` Al Viro
2017-09-10 20:07 ` Dave Jones
2017-09-10 20:33 ` Al Viro
2017-09-10 21:11 ` Dave Chinner
2017-09-10 21:19 ` Al Viro
2017-09-10 22:08 ` Dave Chinner
2017-09-10 23:07 ` Al Viro
2017-09-10 23:15 ` Al Viro
2017-09-11 0:31 ` Dave Chinner
2017-09-11 3:32 ` Al Viro
2017-09-11 6:44 ` Dave Chinner
2017-09-11 20:07 ` Al Viro
2017-09-11 20:17 ` Al Viro [this message]
2017-09-12 6:02 ` Dave Chinner
2017-09-12 11:13 ` Al Viro
2017-09-11 12:07 ` Christoph Hellwig
2017-09-11 12:51 ` Al Viro
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