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[2/3] btrfs: allocate root item at snapshot ioctl time

Message ID df7bb4de0c195b9314b9d0256038a955f791eb31.1447177256.git.dsterba@suse.com (mailing list archive)
State Accepted
Headers show

Commit Message

David Sterba Nov. 10, 2015, 5:54 p.m. UTC 
The actual snapshot creation is delayed until transaction commit. If we
cannot get enough memory for the root item there, we have to fail the
whole transaction commit which is bad. So we'll allocate the memory at
the ioctl call and pass it along with the pending_snapshot struct. The
potential ENOMEM will be returned to the caller of snapshot ioctl.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ioctl.c       | 9 +++++++++
 fs/btrfs/transaction.c | 9 +++------
 fs/btrfs/transaction.h | 1 +
 3 files changed, 13 insertions(+), 6 deletions(-)
diff mbox

Patch

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index bf7d8ba7dd00..040faa8eebc9 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -659,6 +659,13 @@  static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 	if (!pending_snapshot)
 		return -ENOMEM;
 
+	pending_snapshot->root_item = kzalloc(sizeof(struct btrfs_root_item),
+			GFP_NOFS);
+	if (!pending_snapshot->root_item) {
+		ret = -ENOMEM;
+		goto free_pending;
+	}
+
 	atomic_inc(&root->will_be_snapshoted);
 	smp_mb__after_atomic();
 	btrfs_wait_for_no_snapshoting_writes(root);
@@ -738,6 +745,8 @@  static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 dec_and_free:
 	if (atomic_dec_and_test(&root->will_be_snapshoted))
 		wake_up_atomic_t(&root->will_be_snapshoted);
+free_pending:
+	kfree(pending_snapshot->root_item);
 	kfree(pending_snapshot);
 
 	return ret;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a5b06442f0bf..09129b65dd4b 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1320,11 +1320,8 @@  static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 		return 0;
 	}
 
-	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
-	if (!new_root_item) {
-		pending->error = -ENOMEM;
-		goto root_item_alloc_fail;
-	}
+	ASSERT(pending->root_item);
+	new_root_item = pending->root_item;
 
 	pending->error = btrfs_find_free_objectid(tree_root, &objectid);
 	if (pending->error)
@@ -1557,7 +1554,7 @@  static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_clear_skip_qgroup(trans);
 no_free_objectid:
 	kfree(new_root_item);
-root_item_alloc_fail:
+	pending->root_item = NULL;
 	btrfs_free_path(path);
 	return ret;
 }
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index a994bb097ee5..a4e1c1a40880 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -138,6 +138,7 @@  struct btrfs_pending_snapshot {
 	struct dentry *dentry;
 	struct inode *dir;
 	struct btrfs_root *root;
+	struct btrfs_root_item *root_item;
 	struct btrfs_root *snap;
 	struct btrfs_qgroup_inherit *inherit;
 	/* block reservation for the operation */