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From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: viro@zeniv.linux.org.uk, jaegeuk@kernel.org, chao@kernel.org
Cc: linux-fsdevel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	kernel@collabora.com
Subject: [PATCH 2/2] f2fs: Return EOF on unaligned end of file DIO read
Date: Wed, 19 Aug 2020 16:07:31 -0400	[thread overview]
Message-ID: <20200819200731.2972195-3-krisman@collabora.com> (raw)
In-Reply-To: <20200819200731.2972195-1-krisman@collabora.com>

Reading past end of file returns EOF for aligned reads but -EINVAL for
unaligned reads on f2fs.  While documentation is not strict about this
corner case, most filesystem returns EOF on this case, like iomap
filesystems.  This patch consolidates the behavior for f2fs, by making
it return EOF(0).

it can be verified by a read loop on a file that does a partial read
before EOF (A file that doesn't end at an aligned address).  The
following code fails on an unaligned file on f2fs, but not on
btrfs, ext4, and xfs.

  while (done < total) {
    ssize_t delta = pread(fd, buf + done, total - done, off + done);
    if (!delta)
      break;
    ...
  }

It is arguable whether filesystems should actually return EOF or
-EINVAL, but since iomap filesystems support it, and so does the
original DIO code, it seems reasonable to consolidate on that.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 fs/f2fs/data.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5f527073143e..d9834ffe1da9 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3510,6 +3510,9 @@ static int check_direct_IO(struct inode *inode, struct iov_iter *iter,
 	unsigned long align = offset | iov_iter_alignment(iter);
 	struct block_device *bdev = inode->i_sb->s_bdev;
 
+	if (iov_iter_rw(iter) == READ && offset >= i_size_read(inode))
+		return 1;
+
 	if (align & blocksize_mask) {
 		if (bdev)
 			blkbits = blksize_bits(bdev_logical_block_size(bdev));
-- 
2.28.0


  parent reply	other threads:[~2020-08-19 20:07 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 20:07 [PATCH 0/2] Consolidate DIO behavior on unaligned EOF read Gabriel Krisman Bertazi
2020-08-19 20:07 ` [PATCH 1/2] direct-io: defer alignment check until after EOF check Gabriel Krisman Bertazi
2020-08-26 14:28   ` Jan Kara
2020-08-19 20:07 ` Gabriel Krisman Bertazi [this message]
2020-08-20 16:13   ` [PATCH 2/2] f2fs: Return EOF on unaligned end of file DIO read Jaegeuk Kim
2020-08-21  1:37   ` Chao Yu

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