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* [PATCH] inotify: fix deadlock found by lockdepArjan van de Ven2006-07-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is a real deadlock, a nice complex one: (warning: long explanation follows so that Andrew can have a complete patch description) it's an ABCDA deadlock: A iprune_mutex B inode->inotify_mutex C ih->mutex D dev->ev_mutex The AB relationship comes straight from invalidate_inodes() int invalidate_inodes(struct super_block * sb) { int busy; LIST_HEAD(throw_away); mutex_lock(&iprune_mutex); spin_lock(&inode_lock); inotify_unmount_inodes(&sb->s_inodes); where inotify_umount_inodes() takes the mutex_lock(&inode->inotify_mutex); The BC relationship comes directly from inotify_find_update_watch(): s32 inotify_find_update_watch(struct inotify_handle *ih, struct inode *inode, u32 mask) { ... mutex_lock(&inode->inotify_mutex); mutex_lock(&ih->mutex); The CD relationship comes from inotify_rm_wd: inotify_rm_wd does mutex_lock(&inode->inotify_mutex); mutex_lock(&ih->mutex) and then calls inotify_remove_watch_locked() which calls notify_dev_queue_event() which does mutex_lock(&dev->ev_mutex); (this strictly is a BCD relationship) The DA relationship comes from the most interesting part: [<ffffffff8022d9f2>] shrink_icache_memory+0x42/0x270 [<ffffffff80240dc4>] shrink_slab+0x11d/0x1c9 [<ffffffff802b5104>] try_to_free_pages+0x187/0x244 [<ffffffff8020efed>] __alloc_pages+0x1cd/0x2e0 [<ffffffff8025e1f8>] cache_alloc_refill+0x3f8/0x821 [<ffffffff8020a5e5>] kmem_cache_alloc+0x85/0xcb [<ffffffff802db027>] kernel_event+0x2e/0x122 [<ffffffff8021d61c>] inotify_dev_queue_event+0xcc/0x140 inotify_dev_queue_event schedules a kernel_event which does a kmem_cache_alloc( , GFP_KERNEL) which may try to shrink slabs, including the inode cache .. which then takes iprune_mutex. And voila, there is an AB, a BC, a CD relationship (even a direct BCD), and also now a DA relationship -> a circular type AB-BA deadlock but involving 4 locks. The solution is simple: kernel_event() is NOT allowed to use GFP_KERNEL, but must use GFP_NOFS to not cause recursion into the VFS. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Robert Love <rml@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] VFS: Permit filesystem to override root dentry on mountDavid Howells2006-06-231-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] inotify (3/5): add interfaces to kernel APIAmy Griffis2006-06-201-0/+1
| | | | | | | | | | | | | | | | | Add inotify_init_watch() so caller can use inotify_watch refcounts before calling inotify_add_watch(). Add inotify_find_watch() to find an existing watch for an (ih,inode) pair. This is similar to inotify_find_update_watch(), but does not update the watch's mask if one is found. Add inotify_rm_watch() to remove a watch via the watch pointer instead of the watch descriptor. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (2/5): add name's inode to event handlerAmy Griffis2006-06-201-1/+2
| | | | | | | | | | When an inotify event includes a dentry name, also include the inode associated with that name. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (1/5): split kernel API from userspace supportAmy Griffis2006-06-201-0/+717
The following series of patches introduces a kernel API for inotify, making it possible for kernel modules to benefit from inotify's mechanism for watching inodes. With these patches, inotify will maintain for each caller a list of watches (via an embedded struct inotify_watch), where each inotify_watch is associated with a corresponding struct inode. The caller registers an event handler and specifies for which filesystem events their event handler should be called per inotify_watch. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>