btrfs: preallocate path for snapshot creation at ioctl time

We can also preallocate btrfs_path that's used during pending snapshot
creation and avoid another late ENOMEM failure.

Signed-off-by: David Sterba <dsterba@suse.com>

3 files changed, 8 insertions, 6 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 27fc660b0ff3..3d9b27d2176e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -661,7 +661,8 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 
         pending_snapshot->root_item = kzalloc(sizeof(struct btrfs_root_item),
                         GFP_NOFS);
-        if (!pending_snapshot->root_item) {
+        pending_snapshot->path = btrfs_alloc_path();
+        if (!pending_snapshot->root_item || !pending_snapshot->path) {
                 ret = -ENOMEM;
                 goto free_pending;
         }
@@ -747,6 +748,7 @@ dec_and_free:
                 wake_up_atomic_t(&root->will_be_snapshoted);
 free_pending:
         kfree(pending_snapshot->root_item);
+        btrfs_free_path(pending_snapshot->path);
         kfree(pending_snapshot);
 
         return ret;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 2074106122d9..be463b7f1f30 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1319,11 +1319,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         u64 root_flags;
         uuid_le new_uuid;
 
-        path = btrfs_alloc_path();
-        if (!path) {
-                pending->error = -ENOMEM;
-                return 0;
-        }
+        ASSERT(pending->path);
+        path = pending->path;
 
         ASSERT(pending->root_item);
         new_root_item = pending->root_item;
@@ -1561,6 +1558,8 @@ no_free_objectid:
         kfree(new_root_item);
         pending->root_item = NULL;
         btrfs_free_path(path);
+        pending->path = NULL;
+
         return ret;
 }
 
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index b6f9a3c94468..72be51f7ca2f 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -140,6 +140,7 @@ struct btrfs_pending_snapshot {
         struct btrfs_root_item *root_item;
         struct btrfs_root *snap;
         struct btrfs_qgroup_inherit *inherit;
+        struct btrfs_path *path;
         /* block reservation for the operation */
         struct btrfs_block_rsv block_rsv;
         u64 qgroup_reserved;