btrfs: allocate backref_ctx on stack in find_extent_clone

Instead of using kmalloc() to allocate backref_ctx, allocate backref_ctx
on stack. The size is reasonably small.

sizeof(backref_ctx) = 48

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 75cff564dedfbf31b22b6c800694296c05b9cde9..72f9b865e84790fdb6e4187ad82e271999961abc 100644 (file)
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1307,7 +1307,7 @@ static int find_extent_clone(struct send_ctx *sctx,
        u64 flags = 0;
        struct btrfs_file_extent_item *fi;
        struct extent_buffer *eb = path->nodes[0];
-       struct backref_ctx *backref_ctx = NULL;
+       struct backref_ctx backref_ctx = {0};
        struct clone_root *cur_clone_root;
        struct btrfs_key found_key;
        struct btrfs_path *tmp_path;
@@ -1322,12 +1322,6 @@ static int find_extent_clone(struct send_ctx *sctx,
        /* We only use this path under the commit sem */
        tmp_path->need_commit_sem = 0;
 
-       backref_ctx = kmalloc(sizeof(*backref_ctx), GFP_KERNEL);
-       if (!backref_ctx) {
-               ret = -ENOMEM;
-               goto out;
-       }
-
        if (data_offset >= ino_size) {
                /*
                 * There may be extents that lie behind the file's size.
@@ -1392,12 +1386,12 @@ static int find_extent_clone(struct send_ctx *sctx,
                cur_clone_root->found_refs = 0;
        }
 
-       backref_ctx->sctx = sctx;
-       backref_ctx->found = 0;
-       backref_ctx->cur_objectid = ino;
-       backref_ctx->cur_offset = data_offset;
-       backref_ctx->found_itself = 0;
-       backref_ctx->extent_len = num_bytes;
+       backref_ctx.sctx = sctx;
+       backref_ctx.found = 0;
+       backref_ctx.cur_objectid = ino;
+       backref_ctx.cur_offset = data_offset;
+       backref_ctx.found_itself = 0;
+       backref_ctx.extent_len = num_bytes;
 
        /*
         * The last extent of a file may be too large due to page alignment.
@@ -1405,7 +1399,7 @@ static int find_extent_clone(struct send_ctx *sctx,
         * __iterate_backrefs work.
         */
        if (data_offset + num_bytes >= ino_size)
-               backref_ctx->extent_len = ino_size - data_offset;
+               backref_ctx.extent_len = ino_size - data_offset;
 
        /*
         * Now collect all backrefs.
@@ -1416,12 +1410,12 @@ static int find_extent_clone(struct send_ctx *sctx,
                extent_item_pos = 0;
        ret = iterate_extent_inodes(fs_info, found_key.objectid,
                                    extent_item_pos, 1, __iterate_backrefs,
-                                   backref_ctx, false);
+                                   &backref_ctx, false);
 
        if (ret < 0)
                goto out;
 
-       if (!backref_ctx->found_itself) {
+       if (!backref_ctx.found_itself) {
                /* found a bug in backref code? */
                ret = -EIO;
                btrfs_err(fs_info,
@@ -1434,7 +1428,7 @@ static int find_extent_clone(struct send_ctx *sctx,
                    "find_extent_clone: data_offset=%llu, ino=%llu, num_bytes=%llu, logical=%llu",
                    data_offset, ino, num_bytes, logical);
 
-       if (!backref_ctx->found)
+       if (!backref_ctx.found)
                btrfs_debug(fs_info, "no clones found");
 
        cur_clone_root = NULL;
@@ -1458,7 +1452,6 @@ static int find_extent_clone(struct send_ctx *sctx,
 
 out:
        btrfs_free_path(tmp_path);
-       kfree(backref_ctx);
        return ret;
 }