[3/5] btrfs: scrub: add memalloc_nofs protection around init_ipath
diff mbox

Message ID 6174e7ce0e55e54a1a4c3a6be413885495926728.1496252765.git.dsterba@suse.com
State New
Headers show

Commit Message

David Sterba May 31, 2017, 5:49 p.m. UTC
init_ipath is called from a safe ioctl context and from scrub when
printing an error.  The protection is added for three reasons:

* init_data_container calls vmalloc and this does not work as expected
  in the GFP_NOFS context, so this silently does GFP_KERNEL and might
  deadlock in some cases
* keep the context constraint of GFP_NOFS, used by scrub
* we want to use GFP_KERNEL unconditionally inside init_ipath or its
  callees

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

Anand Jain June 1, 2017, 9:27 a.m. UTC | #1
On 06/01/17 01:49, David Sterba wrote:
> init_ipath is called from a safe ioctl context and from scrub when
> printing an error.  The protection is added for three reasons:
>
> * init_data_container calls vmalloc and this does not work as expected
>   in the GFP_NOFS context, so this silently does GFP_KERNEL and might
>   deadlock in some cases
> * keep the context constraint of GFP_NOFS, used by scrub
> * we want to use GFP_KERNEL unconditionally inside init_ipath or its
>   callees

  Reviewed-by: Anand Jain <anand.jain@oracle.com>

Thanks, Anand


> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/scrub.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index e99be644b19f..096e503e3ddc 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -18,6 +18,7 @@
>
>  #include <linux/blkdev.h>
>  #include <linux/ratelimit.h>
> +#include <linux/sched/mm.h>
>  #include "ctree.h"
>  #include "volumes.h"
>  #include "disk-io.h"
> @@ -733,6 +734,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
>  	u32 nlink;
>  	int ret;
>  	int i;
> +	unsigned nofs_flag;
>  	struct extent_buffer *eb;
>  	struct btrfs_inode_item *inode_item;
>  	struct scrub_warning *swarn = warn_ctx;
> @@ -771,7 +773,14 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
>  	nlink = btrfs_inode_nlink(eb, inode_item);
>  	btrfs_release_path(swarn->path);
>
> +	/*
> +	 * init_path might indirectly call vmalloc, or use GFP_KERNEL. Scrub
> +	 * uses GFP_NOFS in this context, so we keep it consistent but it does
> +	 * not seem to be strictly necessary.
> +	 */
> +	nofs_flag = memalloc_nofs_save();
>  	ipath = init_ipath(4096, local_root, swarn->path);
> +	memalloc_nofs_restore(nofs_flag);
>  	if (IS_ERR(ipath)) {
>  		ret = PTR_ERR(ipath);
>  		ipath = NULL;
>
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Patch
diff mbox

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index e99be644b19f..096e503e3ddc 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -18,6 +18,7 @@ 
 
 #include <linux/blkdev.h>
 #include <linux/ratelimit.h>
+#include <linux/sched/mm.h>
 #include "ctree.h"
 #include "volumes.h"
 #include "disk-io.h"
@@ -733,6 +734,7 @@  static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 	u32 nlink;
 	int ret;
 	int i;
+	unsigned nofs_flag;
 	struct extent_buffer *eb;
 	struct btrfs_inode_item *inode_item;
 	struct scrub_warning *swarn = warn_ctx;
@@ -771,7 +773,14 @@  static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 	nlink = btrfs_inode_nlink(eb, inode_item);
 	btrfs_release_path(swarn->path);
 
+	/*
+	 * init_path might indirectly call vmalloc, or use GFP_KERNEL. Scrub
+	 * uses GFP_NOFS in this context, so we keep it consistent but it does
+	 * not seem to be strictly necessary.
+	 */
+	nofs_flag = memalloc_nofs_save();
 	ipath = init_ipath(4096, local_root, swarn->path);
+	memalloc_nofs_restore(nofs_flag);
 	if (IS_ERR(ipath)) {
 		ret = PTR_ERR(ipath);
 		ipath = NULL;