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btrfs: scrub: add memalloc_nofs protection around init_ipath

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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>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2017-05-31 19:21:38 +02:00
parent f11f74416a
commit de2491fdef
1 changed files with 9 additions and 0 deletions
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9
fs/btrfs/scrub.c
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@ -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;