[PATCH 3/3] btrfs: preallocate path for snapshot creation at ioctl time

[David Sterba]

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

Signed-off-by: David Sterba <dste...@suse.com>
---
 fs/btrfs/ioctl.c       | 4 +++-
 fs/btrfs/transaction.c | 9 ++++-----
 fs/btrfs/transaction.h | 1 +
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 040faa8eebc9..d318971d3085 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 @@ static int create_snapshot(struct btrfs_root *root, struct 
inode *dir,
                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 09129b65dd4b..732ad46bf015 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1314,11 +1314,8 @@ 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;
@@ -1556,6 +1553,8 @@ static noinline int create_pending_snapshot(struct 
btrfs_trans_handle *trans,
        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 a4e1c1a40880..9c94344fe204 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -141,6 +141,7 @@ 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;
-- 
2.6.2

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