| Message ID | 20181213211645.14713-1-fdmanana@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Btrfs: setup a nofs context for memory allocation at btrfs_create_tree() | expand |
On 13.12.18 г. 23:16 ч., fdmanana@kernel.org wrote: > From: Filipe Manana <fdmanana@suse.com> > > 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") > Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: Nikolay Borisov <nborisov@suse.com> > --- > fs/btrfs/disk-io.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 67afeaf28a41..3e1b846156dd 100644 > --- 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" > @@ -1235,10 +1236,17 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans, > 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); > >
On Thu, Dec 13, 2018 at 09:16:45PM +0000, fdmanana@kernel.org wrote: > From: Filipe Manana <fdmanana@suse.com> > > 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") > Signed-off-by: Filipe Manana <fdmanana@suse.com> Added to misc-next, thanks. Regarding this class of bugs, I'm not sure if I mentioned it or not, the long-term fix is to set NOFS in transaction start and restore at end/commit. I have a wip patch but not near completion so until then the individual callsites need to be handled.
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 67afeaf28a41..3e1b846156dd 100644 --- 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" @@ -1235,10 +1236,17 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans, 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);