On 10 August 2015 at 11:43, Jan Kara <jack@xxxxxxx> wrote: > On Sun 09-08-15 10:49:33, Sasha Levin wrote: >> I saw the following warning while fuzzing with trinity: >> >> [385644.689209] WARNING: CPU: 1 PID: 23536 at mm/truncate.c:740 pagecache_isize_extended+0x124/0x180() >> [385644.691780] Modules linked in: >> [385644.692695] CPU: 1 PID: 23536 Comm: trinity-c242 Not tainted 4.2.0-rc5-next-20150806-sasha-00040-g1b47b00-dirty #2417 >> [385644.695636] ffffffffb21300e0 ffff8800ba3cfc40 ffffffffb1e89dfc 0000000000000000 >> [385644.708128] ffff8800ba3cfc80 ffffffffa8325106 ffffffffa869fdd4 ffff88006bbe1f10 >> [385644.710046] 0000000000001007 ffff88006bbe1f60 ffff88006bbe1f10 ffff8803daa965a0 >> [385644.722774] Call Trace: >> [385644.723591] dump_stack (lib/dump_stack.c:52) >> [385644.725180] warn_slowpath_common (kernel/panic.c:448) >> [385644.728983] warn_slowpath_null (kernel/panic.c:482) >> [385644.730679] pagecache_isize_extended (mm/truncate.c:740 (discriminator 1)) >> [385644.732630] truncate_setsize (mm/truncate.c:710) >> [385644.734469] v9fs_vfs_setattr_dotl (fs/9p/v9fs_vfs.h:81 fs/9p/vfs_inode_dotl.c:593) >> [385644.753009] notify_change (fs/attr.c:270) >> [385644.754303] do_truncate (fs/open.c:64) >> [385644.759181] do_sys_ftruncate.constprop.5 (fs/open.c:193) >> [385644.760669] SyS_ftruncate (fs/open.c:201) >> [385644.761818] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:186) >> >> But I'm not really sure how that happens... truncate_setsize() changes the inode >> size before calling pagecache_isize_extended(): >> >> i_size_write(inode, newsize); >> if (newsize > oldsize) >> pagecache_isize_extended(inode, oldsize, newsize); >> truncate_pagecache(inode, newsize); >> >> And notify_change() is verifying that i_mutex is held: >> >> WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); >> >> So it doesn't look like a race either. > > Well, looking at the code it can be a race which is specific to 9p > filesystem. It seems to me that 9p can update i_size from > v9fs_refresh_inode_dotl(). That can be called v9fs_lookup_revalidate() > without holding i_mutex. Now I'm not sure d_revalidate() can really race > with truncate on the same inode (whether there isn't something else > protecting this). Al should know better... FWIW I'm still hitting this on latest linus/master (4.9.0-rc7+). Vegard -- 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
