[PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a file opened ro

From	Adam Borowski <kilobyte@angband.pl>
Newsgroups	linux.kernel
Subject	[PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a file opened ro
Date	2016-07-18 00:40 +0200
Message-ID	<rW2T7-6rT-3@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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Instead of checking the mode of the file descriptor, let's check whether it
could have been opened rw.  This allows fixing intermittent exec failures
when deduping a live system: anyone trying to exec a file currently being
deduped gets ETXTBSY.

Issuing this ioctl on a ro file was already allowed for root/cap.

Tested on btrfs and not-yet-merged xfs, as only them implement this ioctl.

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
---
 fs/read_write.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 933b53a..df59dc6 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1723,7 +1723,7 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
 
 		if (info->reserved) {
 			info->status = -EINVAL;
-		} else if (!(is_admin || (dst_file->f_mode & FMODE_WRITE))) {
+		} else if (!(is_admin || !inode_permission(dst, MAY_WRITE))) {
 			info->status = -EINVAL;
 		} else if (file->f_path.mnt != dst_file->f_path.mnt) {
 			info->status = -EXDEV;
-- 
2.8.1

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[PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a file opened ro Adam Borowski <kilobyte@angband.pl> - 2016-07-18 00:40 +0200
  Re: [PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a  file opened ro Adam Borowski <kilobyte@angband.pl> - 2016-07-18 00:40 +0200
  Re: [PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a  file opened ro Mark Fasheh <mfasheh@suse.de> - 2016-07-18 22:00 +0200
  Re: [PATCH] vfs: allow FILE_EXTENT_SAME (dedupe_file_range) on a  file opened ro "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-07-19 04:50 +0200

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