4.19-stable review patch. If anyone has any objections, please let me know.
------------------ From: Filipe Manana <[email protected]> commit b89f6d1fcb30a8cbdc18ce00c7d93792076af453 upstream. We are holding a transaction handle when creating a tree, therefore we can not allocate the root using GFP_KERNEL, as we could deadlock if reclaim is triggered by the allocation, therefore setup a nofs context. Fixes: 74e4d82757f74 ("btrfs: let callers of btrfs_alloc_root pass gfp flags") CC: [email protected] # 4.9+ Reviewed-by: Nikolay Borisov <[email protected]> Signed-off-by: Filipe Manana <[email protected]> Reviewed-by: David Sterba <[email protected]> Signed-off-by: David Sterba <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/btrfs/disk-io.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -17,6 +17,7 @@ #include <linux/semaphore.h> #include <linux/error-injection.h> #include <linux/crc32c.h> +#include <linux/sched/mm.h> #include <asm/unaligned.h> #include "ctree.h" #include "disk-io.h" @@ -1236,10 +1237,17 @@ struct btrfs_root *btrfs_create_tree(str struct btrfs_root *tree_root = fs_info->tree_root; struct btrfs_root *root; struct btrfs_key key; + unsigned int nofs_flag; int ret = 0; uuid_le uuid = NULL_UUID_LE; + /* + * We're holding a transaction handle, so use a NOFS memory allocation + * context to avoid deadlock if reclaim happens. + */ + nofs_flag = memalloc_nofs_save(); root = btrfs_alloc_root(fs_info, GFP_KERNEL); + memalloc_nofs_restore(nofs_flag); if (!root) return ERR_PTR(-ENOMEM);
