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From: Calvin Owens <calvinowens@fb.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: <linux-xfs@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>,
	Dave Chinner <david@fromorbit.com>, <kernel-team@fb.com>,
	<stable@vger.kernel.org>
Subject: [PATCH] xfs: Honor FALLOC_FL_KEEP_SIZE when punching ends of files
Date: Fri, 17 Mar 2017 18:24:48 -0700	[thread overview]
Message-ID: <22a11e65fd5037498a78de61f3ed4dae466ad854.1489791330.git.calvinowens@fb.com> (raw)

Commit 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes") replaced
xfs_zero_remaining_bytes() with calls to iomap helpers.

Unfortunately the new iomap helpers don't enforce that [pos,count) lies
strictly on [0,i_size). This causes fallocate(mode=PUNCH_HOLE|KEEP_SIZE)
calls touching [i_size & ~PAGE_MASK, OFF_T_MAX] to round i_size up to
the nearest multiple of PAGE_SIZE:

  calvinow@vm-disks/generic-xfs-1 ~$ dd if=/dev/urandom of=test bs=2048 count=1
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 2048            Blocks: 8          IO Block: 4096   regular file
  calvinow@vm-disks/generic-xfs-1 ~$ fallocate -n -l 2048 -o 2048 -p test
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 4096            Blocks: 8          IO Block: 4096   regular file

Fix this by reintroducing the checks xfs_zero_remaining_bytes() did
against i_size into xfs_zero_range().

Reported-by: Aaron Gao <gzh@fb.com>
Fixes: 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes")
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org> # 4.8+
Signed-off-by: Calvin Owens <calvinowens@fb.com>
---
 fs/xfs/xfs_file.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 35703a8..da7cd27 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -58,6 +58,17 @@ xfs_zero_range(
 	xfs_off_t		count,
 	bool			*did_zero)
 {
+	/*
+	 * Avoid doing I/O beyond eof - it's not necessary
+	 * since nothing can read beyond eof.  The space will
+	 * be zeroed when the file is extended anyway.
+	 */
+	if (pos >= XFS_ISIZE(ip))
+		return 0;
+
+	if ((pos + count) >= XFS_ISIZE(ip))
+		count = XFS_ISIZE(ip) - pos - 1;
+
 	return iomap_zero_range(VFS_I(ip), pos, count, NULL, &xfs_iomap_ops);
 }
 
-- 
2.9.3

WARNING: multiple messages have this Message-ID (diff)
From: Calvin Owens <calvinowens@fb.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>,
	Dave Chinner <david@fromorbit.com>,
	kernel-team@fb.com, stable@vger.kernel.org
Subject: [PATCH] xfs: Honor FALLOC_FL_KEEP_SIZE when punching ends of files
Date: Fri, 17 Mar 2017 18:24:48 -0700	[thread overview]
Message-ID: <22a11e65fd5037498a78de61f3ed4dae466ad854.1489791330.git.calvinowens@fb.com> (raw)

Commit 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes") replaced
xfs_zero_remaining_bytes() with calls to iomap helpers.

Unfortunately the new iomap helpers don't enforce that [pos,count) lies
strictly on [0,i_size). This causes fallocate(mode=PUNCH_HOLE|KEEP_SIZE)
calls touching [i_size & ~PAGE_MASK, OFF_T_MAX] to round i_size up to
the nearest multiple of PAGE_SIZE:

  calvinow@vm-disks/generic-xfs-1 ~$ dd if=/dev/urandom of=test bs=2048 count=1
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 2048            Blocks: 8          IO Block: 4096   regular file
  calvinow@vm-disks/generic-xfs-1 ~$ fallocate -n -l 2048 -o 2048 -p test
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 4096            Blocks: 8          IO Block: 4096   regular file

Fix this by reintroducing the checks xfs_zero_remaining_bytes() did
against i_size into xfs_zero_range().

Reported-by: Aaron Gao <gzh@fb.com>
Fixes: 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes")
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org> # 4.8+
Signed-off-by: Calvin Owens <calvinowens@fb.com>
---
 fs/xfs/xfs_file.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 35703a8..da7cd27 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -58,6 +58,17 @@ xfs_zero_range(
 	xfs_off_t		count,
 	bool			*did_zero)
 {
+	/*
+	 * Avoid doing I/O beyond eof - it's not necessary
+	 * since nothing can read beyond eof.  The space will
+	 * be zeroed when the file is extended anyway.
+	 */
+	if (pos >= XFS_ISIZE(ip))
+		return 0;
+
+	if ((pos + count) >= XFS_ISIZE(ip))
+		count = XFS_ISIZE(ip) - pos - 1;
+
 	return iomap_zero_range(VFS_I(ip), pos, count, NULL, &xfs_iomap_ops);
 }
 
-- 
2.9.3


             reply	other threads:[~2017-03-18  3:51 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-18  1:24 Calvin Owens [this message]
2017-03-18  1:24 ` [PATCH] xfs: Honor FALLOC_FL_KEEP_SIZE when punching ends of files Calvin Owens
2017-03-18  2:54 ` Calvin Owens
2017-03-20  4:54 ` [PATCH v2] " Calvin Owens
2017-03-20  4:54   ` Calvin Owens
2017-03-21 11:39   ` Brian Foster
2017-03-21 19:13     ` Calvin Owens
2017-03-21 19:13       ` Calvin Owens
2017-03-31  4:18       ` [PATCH v3] " Calvin Owens
2017-03-31  4:18         ` Calvin Owens
2017-03-31  6:51         ` Christoph Hellwig
2017-04-03 17:15         ` Darrick J. Wong
2017-04-03 17:18           ` Darrick J. Wong
2017-04-03 18:54             ` Christoph Hellwig

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