Messages in this thread Patch in this message | | | Date | Mon, 15 Sep 2008 00:12:31 +0200 | From | Nick Piggin <> | Subject | [patch] mm: tiny-shmem fix lor, mmap_sem vs i_mutex |
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On Sun, Sep 14, 2008 at 10:06:31AM +0200, Ingo Molnar wrote: > > * Andrew Morton <akpm@linux-foundation.org> wrote: > > > > [ 6460.634452] > > > [ 6460.634465] ======================================================= > > > [ 6460.634494] [ INFO: possible circular locking dependency detected ] > > > [ 6460.634517] 2.6.27-rc6-tip-00290-g8e229c3-dirty #1 > > > [ 6460.634535] ------------------------------------------------------- > > > [ 6460.634555] gdm-simple-gree/4778 is trying to acquire lock: > > > [ 6460.634574] (&mm->mmap_sem){----}, at: [<c018fe33>] might_fault+0x36/0x73 > > > [ 6460.634639] > > > [ 6460.634645] but task is already holding lock: > > > [ 6460.634662] (&dev->ev_mutex){--..}, at: [<c01c7a76>] inotify_read+0xd8/0x16e > > > [ 6460.634715] > > > [ 6460.634721] which lock already depends on the new lock. > > > > Yes, there's a thread in my intray called "inotify_read's ev_mutex vs > > do_page_fault's mmap_sem...". It's a bit flakey-looking, but there's > > a patch in there. > > ah, thx. I picked up the patch into tip/out-of-tree. (see below for a > tided up changelog) Please queue it up as v2.6.27 material. (i'll report > it if anything breaks due to the patch) > > Ingo > > ---------------> > >From 1eb0a42e4eb3283521ee1de99adbf567874b622f Mon Sep 17 00:00:00 2001 > From: Nick Piggin <nickpiggin@yahoo.com.au> > Date: Thu, 11 Sep 2008 06:12:51 +1000 > Subject: [PATCH] mm: fix locking, inotify_read's ev_mutex vs do_page_fault's mmap_sem...
I would call this "fs: fix inotify locking....", it's not really an mm bug if another subsystem misuses mm's APIs. But that's a nitpick.
Here is the other patch I did too.
tiny-shmem calls do_truncate in shmem_file_setup. do_truncate takes i_mutex, and shmem_file_setup is called with mmap_sem held. However i_mutex nests outside mmap_sem.
Copy the code in shmem.c to avoid this problem.
Signed-off-by: Nick Piggin <npiggin@suse.de> --- Index: linux-2.6/mm/tiny-shmem.c =================================================================== --- linux-2.6.orig/mm/tiny-shmem.c +++ linux-2.6/mm/tiny-shmem.c @@ -65,31 +65,25 @@ struct file *shmem_file_setup(char *name if (!dentry) goto put_memory; + error = -ENFILE; + file = get_empty_filp(); + if (!file) + goto put_dentry; + error = -ENOSPC; inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0); if (!inode) - goto put_dentry; - - d_instantiate(dentry, inode); - error = -ENFILE; - file = alloc_file(shm_mnt, dentry, FMODE_WRITE | FMODE_READ, - &ramfs_file_operations); - if (!file) - goto put_dentry; - - inode->i_nlink = 0; /* It is unlinked */ - - /* notify everyone as to the change of file size */ - error = do_truncate(dentry, size, 0, file); - if (error < 0) goto close_file; + d_instantiate(dentry, inode); + inode->i_size = size; + inode->i_nlink = 0; /* It is unlinked */ + init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ, + &ramfs_file_operations); return file; close_file: put_filp(file); - return ERR_PTR(error); - put_dentry: dput(dentry); put_memory:
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