Task A wait for writeback, while writeback Task B send request to fuse.
Task C is expected to serve this request, here it is in direct reclaim
path cause deadlock when system is in low memory.
without __GFP_FS in Task_C break throttle_direct_reclaim with an
HZ timeout.
kswpad (Task_A): writeback(Task_B):
__switch_to+0x14c schedule+0x70
__schedule+0xb5c __fuse_request_send+0x154
schedule+0x70 fuse_simple_request+0x184
bit_wait+0x18 fuse_flush_times+0x114
__wait_on_bit+0x74 fuse_write_inode+0x60
inode_wait_for_writeback+0xa4 __writeback_single_inode+0x3d8
evict+0xa8 writeback_sb_inodes+0x4c0
iput+0x248 __writeback_inodes_wb+0xb0
dentry_unlink_inode+0xdc wb_writeback+0x270
__dentry_kill[jt]+0x110 wb_workfn+0x37c
shrink_dentry_list+0x17c process_one_work+0x284
prune_dcache_sb+0x5c
super_cache_scan+0x11c
do_shrink_slab+0x248
shrink_slab+0x260
shrink_node+0x678
kswapd+0x8ec
kthread+0x140
ret_from_fork+0x10
Task_C:
__switch_to+0x14c
__schedule+0xb5c
schedule+0x70
throttle_direct_reclaim
try_to_free_pages
__perform_reclaim
__alloc_pages_direct_reclaim
__alloc_pages_slowpath
__alloc_pages_nodemask
alloc_pages
fuse_copy_fill+0x168
fuse_dev_do_read+0x37c
fuse_dev_splice_read+0x94
Suggested-by: Wang Mao <quic_maow@xxxxxxxxxxx>
Signed-off-by: Kassey Li <quic_yingangl@xxxxxxxxxxx>
---
fs/fuse/dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 51897427a534..0df7234840c3 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -713,7 +713,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
if (cs->nr_segs >= cs->pipe->max_usage)
return -EIO;
- page = alloc_page(GFP_HIGHUSER);
+ page = alloc_page(GFP_HIGHUSER & ~__GFP_FS);
if (!page)
return -ENOMEM;
--
2.17.1
