Messages in this thread | | | Date | Mon, 5 Mar 2012 21:33:44 +0000 | From | Al Viro <> | Subject | Re: Linus GIT (3.3.0-rc6+) -- INFO: possible circular locking dependency detected |
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On Mon, Mar 05, 2012 at 04:08:55PM -0500, Miles Lane wrote:
> [ 107.839634] -> #1 (&mm->mmap_sem){++++++}: [readdir() grabs ->mmap_sem under ->i_mutex - true, but irrelevant; more to the point, write() on just about anything will grab ->mmap_sem under ->i_mutex, and that one happens for non-directories]
> [ 107.839665] -> #0 (&sb->s_type->i_mutex_key#13){+.+.+.}: [generic_file_aio_write() grabs ->i_mutex after being called from vfs_write(), called from...] > [ 107.839691] [<ffffffff810e6333>] vfs_write+0xa7/0xee > [ 107.839694] [<ffffffffa037f266>] > ecryptfs_write_lower+0x4e/0x73 [ecryptfs] > [ 107.839700] [<ffffffffa03803d3>] > ecryptfs_encrypt_page+0x11c/0x182 [ecryptfs] > [ 107.839704] [<ffffffffa037e967>] > ecryptfs_writepage+0x31/0x73 [ecryptfs] > [ 107.839708] [<ffffffff810b448b>] __writepage+0x12/0x31 > [ 107.839710] [<ffffffff810b4b25>] write_cache_pages+0x1e6/0x310 > [ 107.839713] [<ffffffff810b4c8d>] generic_writepages+0x3e/0x54 > [ 107.839716] [<ffffffff810b5e05>] do_writepages+0x26/0x28 > [ 107.839719] [<ffffffff810ae1e4>] __filemap_fdatawrite_range+0x4e/0x50 > [ 107.839722] [<ffffffff810aed55>] filemap_fdatawrite+0x1a/0x1c > [ 107.839725] [<ffffffff810aed72>] filemap_write_and_wait+0x1b/0x36 > [ 107.839727] [<ffffffffa037c1bb>] > ecryptfs_vma_close+0x17/0x19 [ecryptfs]
Bloody wonderful... That would do it, all right. Forget about readdir(), the deadlock is real and has nothing to do with directories. Ecryptfs bug, AFAICS.
Thread A: mmap something on ecryptfs, dirty it. Thread B: open underlying file for write, later Thread A: munmap() | Thread B: write() (from unrelated buffer)
A holds ->mmap_sem, B holds ->i_mutex. A is blocked essentially on attempt to do what B is doing (write to underlying file; any mutex whatever_fs_write() might be holding around copy_from_user() will do for that deadlock). B is blocked trying to fault some pages in.
Fun...
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