Ryusuke Konishi 572d8b3945 nilfs2: fix deadlock issue between chcp and thaw ioctls ... An fs-thaw ioctl causes deadlock with a chcp or mkcp -s command: chcp D ffff88013870f3d0 0 1325 1324 0x00000004 ... Call Trace: nilfs_transaction_begin+0x11c/0x1a0 [nilfs2] wake_up_bit+0x20/0x20 copy_from_user+0x18/0x30 [nilfs2] nilfs_ioctl_change_cpmode+0x7d/0xcf [nilfs2] nilfs_ioctl+0x252/0x61a [nilfs2] do_page_fault+0x311/0x34c get_unmapped_area+0x132/0x14e do_vfs_ioctl+0x44b/0x490 __set_task_blocked+0x5a/0x61 vm_mmap_pgoff+0x76/0x87 __set_current_blocked+0x30/0x4a sys_ioctl+0x4b/0x6f system_call_fastpath+0x16/0x1b thaw D ffff88013870d890 0 1352 1351 0x00000004 ... Call Trace: rwsem_down_failed_common+0xdb/0x10f call_rwsem_down_write_failed+0x13/0x20 down_write+0x25/0x27 thaw_super+0x13/0x9e do_vfs_ioctl+0x1f5/0x490 vm_mmap_pgoff+0x76/0x87 sys_ioctl+0x4b/0x6f filp_close+0x64/0x6c system_call_fastpath+0x16/0x1b where the thaw ioctl deadlocked at thaw_super() when called while chcp was waiting at nilfs_transaction_begin() called from nilfs_ioctl_change_cpmode(). This deadlock is 100% reproducible. This is because nilfs_ioctl_change_cpmode() first locks sb->s_umount in read mode and then waits for unfreezing in nilfs_transaction_begin(), whereas thaw_super() locks sb->s_umount in write mode. The locking of sb->s_umount here was intended to make snapshot mounts and the downgrade of snapshots to checkpoints exclusive. This fixes the deadlock issue by replacing the sb->s_umount usage in nilfs_ioctl_change_cpmode() with a dedicated mutex which protects snapshot mounts. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2012-07-30 17:25:19 -07:00
..
alloc.c
alloc.h
bmap.c
bmap.h
btnode.c
btnode.h
btree.c
btree.h
cpfile.c	nilfs2: fix timing issue between rmcp and chcp ioctls	2012-07-30 17:25:19 -07:00
cpfile.h
dat.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
dat.h
dir.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
direct.c
direct.h
export.h
file.c	nilfs2: flush disk caches in syncing	2012-05-31 17:49:27 -07:00
gcinode.c	nilfs2: ensure proper cache clearing for gc-inodes	2012-06-20 14:39:35 -07:00
ifile.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
ifile.h
inode.c	vfs: Rename end_writeback() to clear_inode()	2012-05-06 13:43:41 +08:00
ioctl.c	nilfs2: fix deadlock issue between chcp and thaw ioctls	2012-07-30 17:25:19 -07:00
Kconfig
Makefile
mdt.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
mdt.h
namei.c	don't pass nameidata to ->create()	2012-07-14 16:34:47 +04:00
nilfs.h	nilfs: propagate umode_t	2012-01-03 22:55:04 -05:00
page.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
page.h
recovery.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
segbuf.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
segbuf.h
segment.c	nilfs2: ensure proper cache clearing for gc-inodes	2012-06-20 14:39:35 -07:00
segment.h
sufile.c	nilfs2: remove the second argument of k[un]map_atomic()	2012-03-20 21:48:24 +08:00
sufile.h
super.c	nilfs2: fix deadlock issue between chcp and thaw ioctls	2012-07-30 17:25:19 -07:00
the_nilfs.c	nilfs2: fix deadlock issue between chcp and thaw ioctls	2012-07-30 17:25:19 -07:00
the_nilfs.h	nilfs2: fix deadlock issue between chcp and thaw ioctls	2012-07-30 17:25:19 -07:00