Hi, I'm reporting an issue in overlay fs that was introduced in v4.2 (it worked on v4.1): when overlay fs is mounted inside a overlay fs, I get a "no such device or address" error (ENXIO) during open(). After adding some debug printks, I found that the ENXIO comes from fs/inode.c:no_open(). The bug was initially reported on: https://github.com/coreos/rkt/issues/1537 The following commands can reproduce the issue: # mkdir upper lower work merged # mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged/ # cd merged # mkdir upper2 lower2 work2 merged2 # mount -t overlay overlay -olowerdir=lower2,upperdir=upper2,workdir=work2 merged2/ # cd merged2 # echo hello > test.txt bash: test.txt: No such device or address For debugging purposes, I added a "BUG()" in fs/inode.c:no_open() in order to see the stack at the moment the ENXIO is returned: [ 0.446166] Call Trace: [ 0.446166] [<ffffffff8121701f>] do_dentry_open+0x1ff/0x2f0 [ 0.446166] [<ffffffff81232960>] ? inode_init_always+0x1b0/0x1b0 [ 0.446166] [<ffffffff812184c6>] vfs_open+0x56/0x60 [ 0.446166] [<ffffffff812271ee>] path_openat+0x1de/0x1250 [ 0.446166] [<ffffffff8119ee61>] ? filemap_fault+0xb1/0x420 [ 0.446166] [<ffffffff811bcf00>] ? __inc_zone_state+0x20/0x60 [ 0.446166] [<ffffffff81229401>] do_filp_open+0x91/0x100 [ 0.446166] [<ffffffff811fad03>] ? kmem_cache_alloc+0x193/0x210 [ 0.446166] [<ffffffff81228436>] ? getname_flags+0x56/0x1f0 [ 0.446166] [<ffffffff8123634f>] ? __alloc_fd+0x3f/0x100 [ 0.446166] [<ffffffff8121887a>] do_sys_open+0x13a/0x230 [ 0.446166] [<ffffffff8121898e>] SyS_open+0x1e/0x20 [ 0.446166] [<ffffffff81790fee>] entry_SYSCALL_64_fastpath+0x12/0x71 git-bisect found the following: > 4bacc9c9234c7c8eec44f5ed4e960d9f96fa0f01 is the first bad commit > commit 4bacc9c9234c7c8eec44f5ed4e960d9f96fa0f01 > Author: David Howells <dhowells@xxxxxxxxxx> > Date: Thu Jun 18 14:32:31 2015 +0100 > > overlayfs: Make f_path always point to the overlay > and f_inode to the underlay See patch (2) in https://lwn.net/Articles/648525/: > (2) The main VFS patch that makes an open file struct referring to a union > file have ->f_path point to the union/overlay file whilst ->f_inode and > ->f_mapping refer to the subordinate file that does the actual work. Cheers, Alban -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
