There are several ioctls which can work around constraints enforced by
btrfs_swap_activate and lead to an unsafe situation. We cannot do any of
the following on an active swap file in order to avoid creating
compressed or shared extents:
- chattr -C or +c
- snapshot create
- defrag
- clone
- dedup
Signed-off-by: Omar Sandoval <osandov@xxxxxxxxxxx>
---
fs/btrfs/ctree.h | 3 +++
fs/btrfs/disk-io.c | 1 +
fs/btrfs/ioctl.c | 35 +++++++++++++++++++++++++++++++----
3 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fe69edd..38979b9 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1891,6 +1891,9 @@ struct btrfs_root {
int send_in_progress;
struct btrfs_subvolume_writers *subv_writers;
atomic_t will_be_snapshoted;
+
+ /* Number of active swapfiles */
+ atomic_t nr_swapfiles;
};
struct btrfs_ioctl_defrag_range_args {
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1bf9f89..60094c4 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1265,6 +1265,7 @@ static void __setup_root(u32 nodesize, u32 sectorsize, u32 stripesize,
atomic_set(&root->orphan_inodes, 0);
atomic_set(&root->refs, 1);
atomic_set(&root->will_be_snapshoted, 0);
+ atomic_set(&root->nr_swapfiles, 0);
root->log_transid = 0;
root->log_transid_committed = -1;
root->last_log_commit = 0;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4399f0c..18fa95c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -291,9 +291,11 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
} else {
ip->flags |= BTRFS_INODE_NODATACOW;
}
- } else {
+ } else if (!IS_SWAPFILE(inode)) {
/*
- * Revert back under same assuptions as above
+ * Revert back under same assumptions as above. swap_activate
+ * checks that we don't swapon a copy-on-write file, but we also
+ * make sure that it doesn't become copy-on-write here.
*/
if (S_ISREG(mode)) {
if (inode->i_size == 0)
@@ -316,7 +318,12 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
ret = btrfs_set_prop(inode, "btrfs.compression", NULL, 0, 0);
if (ret && ret != -ENODATA)
goto out_drop;
- } else if (flags & FS_COMPR_FL) {
+ } else if (flags & FS_COMPR_FL && !IS_SWAPFILE(inode)) {
+ /*
+ * Like nodatacow, swap_activate checks that we don't swapon a
+ * compressed file, so we shouldn't let it become compressed.
+ */
+
const char *comp;
ip->flags |= BTRFS_INODE_COMPRESS;
@@ -330,7 +337,6 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
comp, strlen(comp), 0);
if (ret)
goto out_drop;
-
} else {
ret = btrfs_set_prop(inode, "btrfs.compression", NULL, 0, 0);
if (ret && ret != -ENODATA)
@@ -647,6 +653,12 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
return -EINVAL;
+ if (atomic_read(&root->nr_swapfiles)) {
+ btrfs_err(root->fs_info,
+ "cannot create snapshot with active swapfile");
+ return -ETXTBSY;
+ }
+
atomic_inc(&root->will_be_snapshoted);
smp_mb__after_atomic();
btrfs_wait_nocow_write(root);
@@ -1292,6 +1304,12 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
compress_type = range->compress_type;
}
+ mutex_lock(&inode->i_mutex);
+ ret = IS_SWAPFILE(inode) ? -ETXTBSY : 0;
+ mutex_unlock(&inode->i_mutex);
+ if (ret)
+ return ret;
+
if (extent_thresh == 0)
extent_thresh = 256 * 1024;
@@ -2927,6 +2945,11 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 len,
btrfs_double_lock(src, loff, dst, dst_loff, len);
+ if (IS_SWAPFILE(src) || IS_SWAPFILE(dst)) {
+ ret = -ETXTBSY;
+ goto out_unlock;
+ }
+
ret = extent_same_check_offsets(src, loff, len);
if (ret)
goto out_unlock;
@@ -3644,6 +3667,10 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
mutex_lock(&src->i_mutex);
}
+ ret = -ETXTBSY;
+ if (IS_SWAPFILE(src) || IS_SWAPFILE(inode))
+ goto out_unlock;
+
/* determine range to clone */
ret = -EINVAL;
if (off + len > src->i_size || off + len < off)
--
2.1.3
--
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