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Linus Torvalds 12f8ad4b05 vfs: clean up __d_lookup_rcu() and dentry_cmp() interfaces 
The calling conventions for __d_lookup_rcu() and dentry_cmp() are
annoying in different ways, and there is actually one single underlying
reason for both of the annoyances.

The fundamental reason is that we do the returned dentry sequence number
check inside __d_lookup_rcu() instead of doing it in the caller.  This
results in two annoyances:

 - __d_lookup_rcu() now not only needs to return the dentry and the
   sequence number that goes along with the lookup, it also needs to
   return the inode pointer that was validated by that sequence number
   check.

 - and because we did the sequence number check early (to validate the
   name pointer and length) we also couldn't just pass the dentry itself
   to dentry_cmp(), we had to pass the counted string that contained the
   name.

So that sequence number decision caused two separate ugly calling
conventions.

Both of these problems would be solved if we just did the sequence
number check in the caller instead.  There's only one caller, and that
caller already has to do the sequence number check for the parent
anyway, so just do that.

That allows us to stop returning the dentry->d_inode in that in-out
argument (pointer-to-pointer-to-inode), so we can make the inode
argument just a regular input inode pointer.  The caller can just load
the inode from dentry->d_inode, and then do the sequence number check
after that to make sure that it's synchronized with the name we looked
up.

And it allows us to just pass in the dentry to dentry_cmp(), which is
what all the callers really wanted.  Sure, dentry_cmp() has to be a bit
careful about the dentry (which is not stable during RCU lookup), but
that's actually very simple.

And now that dentry_cmp() can clearly see that the first string argument
is a dentry, we can use the direct word access for that, instead of the
careful unaligned zero-padding.  The dentry name is always properly
aligned, since it is a single path component that is either embedded
into the dentry itself, or was allocated with kmalloc() (see __d_alloc).

Finally, this also uninlines the nasty slow-case for dentry comparisons:
that one *does* need to do a sequence number check, since it will call
in to the low-level filesystems, and we want to give those a stable
inode pointer and path component length/start arguments.  Doing an extra
sequence check for that slow case is not a problem, though.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-04 18:21:14 -07:00
..
9p 9p changes for the 3.4 merge window 2012-03-28 09:58:38 -07:00
adfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
affs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
afs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
autofs4 autofs: make the autofsv5 packet file descriptor use a packetized pipe 2012-04-29 13:30:08 -07:00
befs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
bfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
btrfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2012-04-28 09:30:07 -07:00
cachefiles switch touch_atime to struct path 2012-03-20 21:29:41 -04:00
ceph Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2012-03-28 10:01:29 -07:00
cifs Use correct conversion specifiers in cifs_show_options 2012-04-24 11:36:25 -05:00
coda Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
configfs make configfs_pin_fs() return root dentry on success 2012-03-20 21:29:48 -04:00
cramfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
debugfs simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
devpts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
dlm dlm fixes for 3.4 2012-04-23 18:22:42 -07:00
ecryptfs ecryptfs: make register_filesystem() the last potential failure exit 2012-03-20 21:29:49 -04:00
efs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
exofs Merge branch 'for-linus' of git://git.open-osd.org/linux-open-osd 2012-03-28 20:04:27 -07:00
exportfs
ext2 migrate ext2_fs.h guts to fs/ext2/ext2.h 2012-03-31 16:03:16 -04:00
ext3 ext3: move headers to fs/ext3/ 2012-03-31 16:03:16 -04:00
ext4 Ext4 bug fixes for 3.4 2012-04-23 19:52:00 -07:00
fat fat: fix bug in enforcing Long File Name length 2012-03-23 16:58:40 -07:00
freevxfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
fscache
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2012-04-18 17:29:05 -07:00
gfs2 GFS2: Instruct DLM to avoid queue convert slowdown 2012-04-24 13:26:50 +01:00
hfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
hfsplus hfsplus: add an ioctl to bless files 2012-03-20 21:29:53 -04:00
hostfs Merge branch 'for-linus-3.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml 2012-03-27 18:29:53 -07:00
hpfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
hppfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
hugetlbfs hugetlbfs: lockdep annotate root inode properly 2012-04-25 21:26:34 -07:00
isofs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
jbd Power management updates for 3.4 2012-03-21 10:15:51 -07:00
jbd2 jbd2: use GFP_NOFS for blkdev_issue_flush 2012-04-23 21:43:41 -04:00
jffs2 MTD merge for 3.4 2012-03-30 17:31:56 -07:00
jfs jfs: mising cleanup on register_filesystem() failure 2012-03-20 21:29:48 -04:00
lockd lockd: fix the endianness bug 2012-04-13 13:50:52 -04:00
logfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
minix Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
ncpfs Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
nfs NFSv4.1: Use the correct hostname in the client identifier string 2012-04-30 12:04:58 -04:00
nfs_common
nfsd nfsd: fix nfs4recover.c printk format warning 2012-04-30 12:28:48 -07:00
nilfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
nls NLS: raname "maxlen" to "maxout" in UTF conversion routines 2011-11-26 19:58:47 -08:00
notify fs/notify/notification.c: make subsys_initcall function static 2012-03-23 16:58:31 -07:00
ntfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
ocfs2 ocfs2: ->e_leaf_clusters endianness breakage 2012-04-13 12:31:43 -04:00
omfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
openpromfs switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
proc revert "proc: clear_refs: do not clear reserved pages" 2012-04-25 21:26:34 -07:00
pstore Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
qnx4 qnx4: new helper - try_extent() 2012-03-20 21:29:52 -04:00
qnx6 fs: initial qnx6fs addition 2012-03-20 21:29:38 -04:00
quota Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2012-03-28 10:00:14 -07:00
ramfs tidy up after d_make_root() conversion 2012-03-20 21:29:37 -04:00
reiserfs Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
romfs MTD merge for 3.4 2012-03-30 17:31:56 -07:00
squashfs Add an extra mount time sanity check, plus some code cleanups and bug fixes. 2012-03-28 18:05:54 -07:00
sysfs sysfs: handle 'parent deleted before child added' 2012-04-10 14:48:51 -07:00
sysv switch open-coded instances of d_make_root() to new helper 2012-03-20 21:29:35 -04:00
ubifs - Improve error messages 2012-03-23 09:27:40 -07:00
udf Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2012-03-28 10:00:14 -07:00
ufs Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
xfs Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
aio.c kill mm argument of vm_munmap() 2012-04-21 01:58:20 -04:00
anon_inodes.c anon_inodes: move allocation of anon_inode into ->mount() 2012-03-20 21:29:45 -04:00
attr.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
bad_inode.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
binfmt_aout.c VM: add "vm_mmap()" helper function 2012-04-20 17:29:13 -07:00
binfmt_elf.c VM: add "vm_mmap()" helper function 2012-04-20 17:29:13 -07:00
binfmt_elf_fdpic.c VM: add "vm_mmap()" helper function 2012-04-20 17:29:13 -07:00
binfmt_em86.c __register_binfmt() made void 2012-03-20 21:29:46 -04:00
binfmt_flat.c VM: add "vm_mmap()" helper function 2012-04-20 17:29:13 -07:00
binfmt_misc.c magic.h: move some FS magic numbers into magic.h 2012-03-23 16:58:31 -07:00
binfmt_script.c __register_binfmt() made void 2012-03-20 21:29:46 -04:00
binfmt_som.c VM: add "vm_mmap()" helper function 2012-04-20 17:29:13 -07:00
bio-integrity.c fs: remove the second argument of k[un]map_atomic() 2012-03-20 21:48:21 +08:00
bio.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
block_dev.c magic.h: move some FS magic numbers into magic.h 2012-03-23 16:58:31 -07:00
buffer.c fs/buffer.c: remove BUG() in possible but rare condition 2012-04-25 21:26:33 -07:00
char_dev.c char_dev.c: fix up some whitespace errors 2011-12-13 11:18:17 -08:00
compat.c Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
compat_binfmt_elf.c
compat_ioctl.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
dcache.c vfs: clean up __d_lookup_rcu() and dentry_cmp() interfaces 2012-05-04 18:21:14 -07:00
dcookies.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
direct-io.c Restore direct_io / truncate locking API 2012-02-23 15:56:21 -08:00
drop_caches.c
eventfd.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
eventpoll.c epoll: clear the tfile_check_list on -ELOOP 2012-04-25 21:26:33 -07:00
exec.c Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-04-04 10:04:42 -07:00
fcntl.c Wrap accesses to the fd_sets in struct fdtable 2012-02-19 10:30:52 -08:00
fhandle.c vfs: prefer ->dentry->d_sb to ->mnt->mnt_sb 2012-01-06 23:16:53 -05:00
fifo.c
file.c Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
file_table.c vfs: drop_file_write_access() made static 2012-03-20 21:29:32 -04:00
filesystems.c vfs: convert fs_supers to hlist 2012-01-03 22:52:39 -05:00
fs-writeback.c trivial writeback fixes 2012-03-28 10:07:27 -07:00
fs_struct.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
generic_acl.c
inode.c trim includes in inode.c 2012-03-20 21:29:51 -04:00
internal.h vfs: protect remounting superblock read-only 2012-01-06 23:20:12 -05:00
ioctl.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
ioprio.c block: strip out locking optimization in put_io_context() 2012-02-07 07:51:30 +01:00
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-03-21 13:36:41 -07:00
Kconfig.binfmt fs: binfmt_elf: create Kconfig variable for PIE randomization 2012-01-10 16:30:51 -08:00
libfs.c dentry leak in simple_fill_super() failure exit 2012-04-09 01:39:22 -04:00
locks.c CIFS: Fix VFS lock usage for oplocked files 2012-04-01 13:54:27 -05:00
Makefile fs: initial qnx6fs addition 2012-03-20 21:29:38 -04:00
mbcache.c
mount.h vfs: keep list of mounts for each superblock 2012-01-06 23:20:12 -05:00
mpage.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
namei.c vfs: clean up __d_lookup_rcu() and dentry_cmp() interfaces 2012-05-04 18:21:14 -07:00
namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-01-08 13:21:22 -08:00
no-block.c
open.c Wrap accesses to the fd_sets in struct fdtable 2012-02-19 10:30:52 -08:00
pipe.c pipes: add a "packetized pipe" mode for writing 2012-04-29 13:12:42 -07:00
pnode.c vfs: switch pnode.h macros to struct mount * 2012-01-03 22:57:11 -05:00
pnode.h vfs: switch pnode.h macros to struct mount * 2012-01-03 22:57:11 -05:00
posix_acl.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
proc_namespace.c vfs: switch ->show_options() to struct dentry * 2012-01-06 23:19:54 -05:00
read_write.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
read_write.h
readdir.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
select.c Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
seq_file.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
signalfd.c epoll: ep_unregister_pollwait() can use the freed pwq->whead 2012-02-24 11:42:50 -08:00
splice.c tcp: tcp_sendpages() should call tcp_push() once 2012-04-05 19:04:27 -04:00
stack.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
stat.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
statfs.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
super.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
sync.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00
timerfd.c
utimes.c
xattr.c fs/xattr.c:setxattr(): improve handling of allocation failures 2012-04-05 15:25:50 -07:00
xattr_acl.c fs: reduce the use of module.h wherever possible 2012-02-28 19:31:58 -05:00