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 <dste...@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;
--
2.12.0
--
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