linux-kernel - [RFC PATCH 2/6] btrfs: don't allow -C or +c chattrs on a swap file

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Date:	Mon, 17 Nov 2014 02:36:55 -0800
From:	Omar Sandoval <osandov@...ndov.com>
To:	linux-btrfs@...r.kernel.org
Cc:	Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
	<linux-fsdevel@...r.kernel.org>,
	Omar Sandoval <osandov@...ndov.com>
Subject: [RFC PATCH 2/6] btrfs: don't allow -C or +c chattrs on a swap file

swap_activate will check for a compressed or copy-on-write file; we shouldn't
allow it to become either once it has already been activated.

Signed-off-by: Omar Sandoval <osandov@...ndov.com>
---
 fs/btrfs/ioctl.c | 50 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e3b458a..7aee8cf 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -293,14 +293,21 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 		}
 	} else {
 		/*
-		 * Revert back under same assuptions as above
+		 * swap_activate checks that we don't swapon a copy-on-write
+		 * file, but we must also make sure that it doesn't become
+		 * copy-on-write.
 		 */
-		if (S_ISREG(mode)) {
-			if (inode->i_size == 0)
-				ip->flags &= ~(BTRFS_INODE_NODATACOW
-				             | BTRFS_INODE_NODATASUM);
-		} else {
-			ip->flags &= ~BTRFS_INODE_NODATACOW;
+		if (!IS_SWAPFILE(inode)) {
+			/*
+			 * Revert back under same assumptions as above
+			 */
+			if (S_ISREG(mode)) {
+				if (inode->i_size == 0)
+					ip->flags &= ~(BTRFS_INODE_NODATACOW |
+						       BTRFS_INODE_NODATASUM);
+			} else {
+				ip->flags &= ~BTRFS_INODE_NODATACOW;
+			}
 		}
 	}
 
@@ -317,20 +324,25 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 		if (ret && ret != -ENODATA)
 			goto out_drop;
 	} else if (flags & FS_COMPR_FL) {
-		const char *comp;
-
-		ip->flags |= BTRFS_INODE_COMPRESS;
-		ip->flags &= ~BTRFS_INODE_NOCOMPRESS;
+		/*
+		 * Like nodatacow, swap_activate checks that we don't swapon a
+		 * compressed file, so we shouldn't let it become compressed.
+		 */
+		if (!IS_SWAPFILE(inode)) {
+			const char *comp;
 
-		if (root->fs_info->compress_type == BTRFS_COMPRESS_LZO)
-			comp = "lzo";
-		else
-			comp = "zlib";
-		ret = btrfs_set_prop(inode, "btrfs.compression",
-				     comp, strlen(comp), 0);
-		if (ret)
-			goto out_drop;
+			ip->flags |= BTRFS_INODE_COMPRESS;
+			ip->flags &= ~BTRFS_INODE_NOCOMPRESS;
 
+			if (root->fs_info->compress_type == BTRFS_COMPRESS_LZO)
+				comp = "lzo";
+			else
+				comp = "zlib";
+			ret = btrfs_set_prop(inode, "btrfs.compression",
+					     comp, strlen(comp), 0);
+			if (ret)
+				goto out_drop;
+		}
 	} else {
 		ret = btrfs_set_prop(inode, "btrfs.compression", NULL, 0, 0);
 		if (ret && ret != -ENODATA)
-- 
2.1.3

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