On Thu, 20 Jan 2011, Miklos Szeredi wrote: > On Thu, 20 Jan 2011, Christoph Hellwig wrote: > > On Thu, Jan 20, 2011 at 01:30:58PM +0100, Miklos Szeredi wrote: > > > > > > Truncate and hole punching already serialize with i_mutex. Other > > > callers of unmap_mapping_range() do not, and it's difficult to get > > > i_mutex protection for all callers. In particular ->d_revalidate(), > > > which calls invalidate_inode_pages2_range() in fuse, may be called > > > with or without i_mutex. > > > > > > Which I think is mostly a fuse problem. I really hate bloating the > > generic inode (into which the address_space is embedded) with another > > mutex for deficits in rather special case filesystems. > > As Hugh pointed out unmap_mapping_range() has grown a varied set of > callers, which are difficult to fix up wrt i_mutex. Fuse was just an > example. > > I don't like the bloat either, but this is the best I could come up > with for fixing this problem generally. If you have a better idea, > please share it. If we start from the point that this is mostly a fuse problem (I expect that a thorough audit will show up a few other filesystems too, but let's start from this point): you cite ->d_revalidate as a particular problem, but can we fix up its call sites so that it is always called either with, or much preferably without, i_mutex held? Though actually I couldn't find where ->d_revalidate() is called while holding i_mutex. Failing that, can fuse down_write i_alloc_sem before calling invalidate_inode_pages2(_range), to achieve the same exclusion? The setattr truncation path takes i_alloc_sem as well as i_mutex, though I'm not certain of its full coverage. I did already consider holding and dropping i_alloc_sem inside invalidate_inode_pages2_range(); but direct-io.c very much wants to take mmap_sem (when get_user_pages_fast goes slow) after taking i_alloc_sem, whereas fuse_direct_mmap() very much wants to call invalidate_inode_pages2() while mmap_sem is held. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>