From: Mel Gorman Date: Tue, 22 Mar 2011 23:30:08 +0000 (-0700) Subject: mm: swap: unlock swapfile inode mutex before closing file on bad swapfiles X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=52c50567d8ab0a0a87f12cceaa4194967854f0bd;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git mm: swap: unlock swapfile inode mutex before closing file on bad swapfiles If an administrator tries to swapon a file backed by NFS, the inode mutex is taken (as it is for any swapfile) but later identified to be a bad swapfile due to the lack of bmap and tries to cleanup. During cleanup, an attempt is made to close the file but with inode->i_mutex still held. Closing an NFS file syncs it which tries to acquire the inode mutex leading to deadlock. If lockdep is enabled the following appears on the console; ============================================= [ INFO: possible recursive locking detected ] 2.6.38-rc8-autobuild #1 --------------------------------------------- swapon/2192 is trying to acquire lock: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: vfs_fsync_range+0x47/0x7c but task is already holding lock: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7 other info that might help us debug this: 1 lock held by swapon/2192: #0: (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7 stack backtrace: Pid: 2192, comm: swapon Not tainted 2.6.38-rc8-autobuild #1 Call Trace: __lock_acquire+0x2eb/0x1623 find_get_pages_tag+0x14a/0x174 pagevec_lookup_tag+0x25/0x2e vfs_fsync_range+0x47/0x7c lock_acquire+0xd3/0x100 vfs_fsync_range+0x47/0x7c nfs_flush_one+0x0/0xdf [nfs] mutex_lock_nested+0x40/0x2b1 vfs_fsync_range+0x47/0x7c vfs_fsync_range+0x47/0x7c vfs_fsync+0x1c/0x1e nfs_file_flush+0x64/0x69 [nfs] filp_close+0x43/0x72 sys_swapon+0xa39/0xae7 sysret_check+0x2e/0x69 system_call_fastpath+0x16/0x1b This patch releases the mutex if its held before calling filep_close() so swapon fails as expected without deadlock when the swapfile is backed by NFS. If accepted for 2.6.39, it should also be considered a -stable candidate for 2.6.38 and 2.6.37. Signed-off-by: Mel Gorman Acked-by: Hugh Dickins Cc: [2.6.37+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/swapfile.c b/mm/swapfile.c index 0341c5700e34..6d6d28c0a72f 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2149,8 +2149,13 @@ bad_swap_2: p->flags = 0; spin_unlock(&swap_lock); vfree(swap_map); - if (swap_file) + if (swap_file) { + if (did_down) { + mutex_unlock(&inode->i_mutex); + did_down = 0; + } filp_close(swap_file, NULL); + } out: if (page && !IS_ERR(page)) { kunmap(page);