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Linus Torvalds 64f371bc31 autofs: make the autofsv5 packet file descriptor use a packetized pipe 
The autofs packet size has had a very unfortunate size problem on x86:
because the alignment of 'u64' differs in 32-bit and 64-bit modes, and
because the packet data was not 8-byte aligned, the size of the autofsv5
packet structure differed between 32-bit and 64-bit modes despite
looking otherwise identical (300 vs 304 bytes respectively).

We first fixed that up by making the 64-bit compat mode know about this
problem in commit a32744d4ab ("autofs: work around unhappy compat
problem on x86-64"), and that made a 32-bit 'systemd' work happily on a
64-bit kernel because everything then worked the same way as on a 32-bit
kernel.

But it turned out that 'automount' had actually known and worked around
this problem in user space, so fixing the kernel to do the proper 32-bit
compatibility handling actually *broke* 32-bit automount on a 64-bit
kernel, because it knew that the packet sizes were wrong and expected
those incorrect sizes.

As a result, we ended up reverting that compatibility mode fix, and
thus breaking systemd again, in commit fcbf94b9de.

With both automount and systemd doing a single read() system call, and
verifying that they get *exactly* the size they expect but using
different sizes, it seemed that fixing one of them inevitably seemed to
break the other.  At one point, a patch I seriously considered applying
from Michael Tokarev did a "strcmp()" to see if it was automount that
was doing the operation.  Ugly, ugly.

However, a prettier solution exists now thanks to the packetized pipe
mode.  By marking the communication pipe as being packetized (by simply
setting the O_DIRECT flag), we can always just write the bigger packet
size, and if user-space does a smaller read, it will just get that
partial end result and the extra alignment padding will simply be thrown
away.

This makes both automount and systemd happy, since they now get the size
they asked for, and the kernel side of autofs simply no longer needs to
care - it could pad out the packet arbitrarily.

Of course, if there is some *other* user of autofs (please, please,
please tell me it ain't so - and we haven't heard of any) that tries to
read the packets with multiple writes, that other user will now be
broken - the whole point of the packetized mode is that one system call
gets exactly one packet, and you cannot read a packet in pieces.

Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Miller <davem@davemloft.net>
Cc: Ian Kent <raven@themaw.net>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2012-04-29 13:30:08 -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
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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 FS-Cache: Fix __fscache_uncache_all_inode_pages()'s outer loop 2011-07-21 10:59:16 -07:00
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: Keep dropped state owners on the LRU list for a while 2012-04-21 13:01:00 -04:00
nfs_common
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nfsd Merge branch 'for-3.4' of git://linux-nfs.org/~bfields/linux 2012-04-19 14:54:52 -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
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
Makefile fs: initial qnx6fs addition 2012-03-20 21:29:38 -04:00
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: fix d_ancestor() case in d_materialize_unique 2012-03-28 09:54:34 -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
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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
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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 switch posix_acl_equiv_mode() to umode_t * 2011-08-01 02:10:06 -04:00
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
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
mbcache.c
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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 Make the "word-at-a-time" helper functions more commonly usable 2012-04-06 13:54:56 -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
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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
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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 timerfd: Fix wakeup of processes when timer is cancelled on clock change 2011-06-14 11:46:14 +02:00
utimes.c
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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