From: Jing Xia <jing.xia@xxxxxxxxxx> Writeback thread and fuse block each other. Writeback thread waits fuse's reply with inode's I_SYNC being held.Fuse enters the slowpath of memory allocation when handle the request and has to wait the inode's I_SYNC is cleared. writeback's backtrace --------------------- PID: 6197 TASK: ed130780 CPU: 3 COMMAND: "kworker/u8:7" #0 [<c0a0bae0>] (__schedule) from [<c0a0bdb0>] #1 [<c0a0bdb0>] (schedule) from [<c03d1330>] #2 [<c03d1330>] (__fuse_request_send) from [<c03d16a0>] #3 [<c03d16a0>] (fuse_simple_request) from [<c03d58fc>] #4 [<c03d58fc>] (fuse_flush_times) from [<c03d95dc>] #5 [<c03d95dc>] (fuse_write_inode) from [<c02df87c>] #6 [<c02df87c>] (__writeback_single_inode) from [<c02dee4c>] #7 [<c02dee4c>] (writeback_sb_inodes) from [<c02df0e8>] #8 [<c02df0e8>] (__writeback_inodes_wb) from [<c02de72c>] #9 [<c02de72c>] (wb_writeback) from [<c02dbafc>] #10 [<c02dbafc>] (wb_workfn) from [<c014d3d0>] #11 [<c014d3d0>] (process_one_work) from [<c014d9b8>] #12 [<c014d9b8>] (worker_thread) from [<c0151e40>] #13 [<c0151e40>] (kthread) from [<c0107648>] fuse's backtrace --------------------- PID: 4412 TASK: c4b47800 CPU: 3 COMMAND: "Thread-9" #0 [<c0a0bae0>] (__schedule) from [<c0a0bdb0>] #1 [<c0a0bdb0>] (schedule) from [<c0a0c74c>] #2 [<c0a0c74c>] (bit_wait) from [<c0a0c310>] #3 [<c0a0c310>] (__wait_on_bit) from [<c02db7d0>] #4 [<c02db7d0>] (__inode_wait_for_writeback) from [<c02db700>] #5 [<c02db700>] (inode_wait_for_writeback) from [<c02cb33c>] #6 [<c02cb33c>] (evict) from [<c02c40fc>] #7 [<c02c40fc>] (__dentry_kill) from [<c02c4430>] #8 [<c02c4430>] (shrink_dentry_list) from [<c02c41dc>] #9 [<c02c41dc>] (prune_dcache_sb) from [<c02af8a0>] #10 [<c02af8a0>] (super_cache_scan) from [<c0258f2c>] #11 [<c0258f2c>] (shrink_slab) from [<c025dc6c>] #12 [<c025dc6c>] (shrink_node) from [<c025b240>] #13 [<c025b240>] (do_try_to_free_pages) from [<c025adc0>] #14 [<c025adc0>] (try_to_free_pages) from [<c0249cb0>] #15 [<c0249cb0>] (__alloc_pages_nodemask) from [<c03d3638>] #16 [<c03d3638>] (fuse_copy_fill) from [<c03d33c0>] #17 [<c03d33c0>] (fuse_copy_one) from [<c03d2fe4>] #18 [<c03d2fe4>] (fuse_dev_do_read) from [<c03d2814>] #19 [<c03d2814>] (fuse_dev_splice_read) from [<c02e2548>] #20 [<c02e2548>] (sys_splice) from [<c0107740>] This patch clears __GFP_FS flag when fuse alloctes pages to avoid deadlock,as super_cache_scan will directly return SHRINK_STOP when __GFP_FS is not set. Signed-off-by: Jing Xia <jing.xia@xxxxxxxxxx> --- 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 02b3c36..165c416 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -708,7 +708,7 @@ 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; -- 1.9.1
