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David Howells 9875cf8064 Add a dentry op to handle automounting rather than abusing follow_link() 
Add a dentry op (d_automount) to handle automounting directories rather than
abusing the follow_link() inode operation.  The operation is keyed off a new
dentry flag (DCACHE_NEED_AUTOMOUNT).

This also makes it easier to add an AT_ flag to suppress terminal segment
automount during pathwalk and removes the need for the kludge code in the
pathwalk algorithm to handle directories with follow_link() semantics.

The ->d_automount() dentry operation:

	struct vfsmount *(*d_automount)(struct path *mountpoint);

takes a pointer to the directory to be mounted upon, which is expected to
provide sufficient data to determine what should be mounted.  If successful, it
should return the vfsmount struct it creates (which it should also have added
to the namespace using do_add_mount() or similar).  If there's a collision with
another automount attempt, NULL should be returned.  If the directory specified
by the parameter should be used directly rather than being mounted upon,
-EISDIR should be returned.  In any other case, an error code should be
returned.

The ->d_automount() operation is called with no locks held and may sleep.  At
this point the pathwalk algorithm will be in ref-walk mode.

Within fs/namei.c itself, a new pathwalk subroutine (follow_automount()) is
added to handle mountpoints.  It will return -EREMOTE if the automount flag was
set, but no d_automount() op was supplied, -ELOOP if we've encountered too many
symlinks or mountpoints, -EISDIR if the walk point should be used without
mounting and 0 if successful.  The path will be updated to point to the mounted
filesystem if a successful automount took place.

__follow_mount() is replaced by follow_managed() which is more generic
(especially with the patch that adds ->d_manage()).  This handles transits from
directories during pathwalk, including automounting and skipping over
mountpoints (and holding processes with the next patch).

__follow_mount_rcu() will jump out of RCU-walk mode if it encounters an
automount point with nothing mounted on it.

follow_dotdot*() does not handle automounts as you don't want to trigger them
whilst following "..".

I've also extracted the mount/don't-mount logic from autofs4 and included it
here.  It makes the mount go ahead anyway if someone calls open() or creat(),
tries to traverse the directory, tries to chdir/chroot/etc. into the directory,
or sticks a '/' on the end of the pathname.  If they do a stat(), however,
they'll only trigger the automount if they didn't also say O_NOFOLLOW.

I've also added an inode flag (S_AUTOMOUNT) so that filesystems can mark their
inodes as automount points.  This flag is automatically propagated to the
dentry as DCACHE_NEED_AUTOMOUNT by __d_instantiate().  This saves NFS and could
save AFS a private flag bit apiece, but is not strictly necessary.  It would be
preferable to do the propagation in d_set_d_op(), but that doesn't normally
have access to the inode.

[AV: fixed breakage in case if __follow_mount_rcu() fails and nameidata_drop_rcu()
succeeds in RCU case of do_lookup(); we need to fall through to non-RCU case after
that, rather than just returning with ungrabbed *path]

Signed-off-by: David Howells <dhowells@redhat.com>
Was-Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:05:03 -05:00
..
ABI Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2011-01-13 20:15:35 -08:00
accounting taskstats: pad taskstats netlink response for aligment issues on ia64 2010-12-22 19:43:34 -08:00
acpi ACPI, APEI, Add APEI generic error status printing support 2010-12-13 23:42:12 -05:00
aoe Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
arm Merge branch 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6 2011-01-06 19:13:58 -08:00
auxdisplay includecheck fix: Documentation, cfag12864b-example.c 2009-09-24 07:20:57 -07:00
blackfin Blackfin: document SPI CS limitations with CPHA=0 2010-08-06 12:55:52 -04:00
block Documentation: remove anticipatory scheduler info 2010-11-11 12:09:59 +01:00
blockdev Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
cdrom Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
cgroups revert documentaion update for memcg's dirty ratio. 2011-01-14 07:52:02 -08:00
connector Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
console doc: fix console doc typo 2010-02-24 13:51:32 +01:00
cpu-freq [CPUFREQ] Processor Clocking Control interface driver 2010-01-13 10:55:16 -05:00
cpuidle
cris
crypto async_tx: add support for asynchronous RAID6 recovery operations 2009-08-29 19:09:27 -07:00
development-process Documentation/development-process: more staging info 2010-11-18 15:00:47 -08:00
device-mapper dm: raid456 basic support 2011-01-13 20:00:02 +00:00
DocBook Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
driver-model driver core: prune docs about device_interface 2010-11-10 16:57:11 -08:00
dvb [media] Documentation/lmedm04: Fix firmware extract information 2010-12-29 08:16:30 -02:00
early-userspace
fault-injection lkdtm: add debugfs access and loosen KPROBE ties 2010-03-06 11:26:32 -08:00
fb Merge branch 'fbdev/udlfb' 2011-01-06 18:10:09 +09:00
filesystems Add a dentry op to handle automounting rather than abusing follow_link() 2011-01-15 20:05:03 -05:00
firmware_class firmware: Update hotplug script 2010-08-05 13:53:34 -07:00
frv
hwmon hwmon: (dme1737) Add support for in7 for SCH5127 2011-01-12 21:55:13 +01:00
i2c i2c: Add generic I2C multiplexer using GPIO API 2011-01-10 22:11:23 +01:00
i2o
ia64 Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
ide ide: preserve Host Protected Area by default (v2) 2009-06-07 13:52:52 +02:00
infiniband Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
input Input: fix force feedback capability query example 2011-01-11 01:07:55 -08:00
ioctl pps: add kernel consumer support 2011-01-13 08:03:21 -08:00
isdn Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-08-04 15:31:02 -07:00
ja_JP Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
kbuild Merge branch 'next-devicetree' of git://git.secretlab.ca/git/linux-2.6 2011-01-10 08:57:03 -08:00
kdump kdump: update kexec-tools URL and Vivek's email 2010-11-25 14:36:38 +01:00
ko_KR Docs/Kconfig: Update: osdl.org -> linuxfoundation.org 2010-11-15 23:50:13 +01:00
kvm Merge branch 'kvm-updates/2.6.38' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2011-01-13 10:14:24 -08:00
laptops thinkpad-acpi: untangle ACPI/vendor backlight selection 2010-08-16 11:54:50 -04:00
leds Documentation: led drivers lp5521 and lp5523 2010-11-12 07:55:32 -08:00
lguest Docs/Kconfig: Update: osdl.org -> linuxfoundation.org 2010-11-15 23:50:13 +01:00
m68k
make kbuild: introduce HDR_ARCH_LIST for headers_install_all 2010-12-14 22:16:19 +01:00
mips
misc-devices Documentation: short descriptions for bh1770glc and apds990x drivers 2010-10-26 16:52:14 -07:00
mmc mmc: add erase, secure erase, trim and secure trim operations 2010-08-12 08:43:30 -07:00
mn10300 trivial: Miscellaneous documentation typo fixes 2009-06-12 18:01:47 +02:00
mtd Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
namespaces
netlabel Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
networking Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
nfc NFC: Driver for NXP Semiconductors PN544 NFC chip. 2011-01-13 08:03:19 -08:00
parisc
PCI Documentation: pci.txt: fix typo 2010-07-11 22:17:45 +02:00
pcmcia pcmcia: use autoconfiguration feature for ioports and iomem 2010-09-29 17:20:24 +02:00
power PM: Fix references to basic-pm-debugging.txt in drivers-testing.txt 2010-12-24 15:02:41 +01:00
powerpc Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
pps pps: add parallel port PPS signal generator 2011-01-13 08:03:21 -08:00
prctl
RCU rcu: update documentation/comments for Lai's adoption patch 2010-11-29 22:01:59 -08:00
s390 Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
scheduler Docs: typo: Complete -> Completely 2010-11-02 22:47:39 -04:00
scsi Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
serial pps: timestamp is always passed to dcd_change() 2011-01-13 08:03:20 -08:00
sh sh: clkfwk: Kill off unused clk_set_rate_ex(). 2010-11-15 18:25:12 +09:00
sound Merge branch 'topic/hda' into for-linus 2011-01-13 08:37:19 +01:00
sparc
spi arm/pxa2xx: reorgazine SSP and SPI header files 2010-12-01 12:18:33 +01:00
sysctl sysctl: remove obsolete comments 2011-01-13 08:03:18 -08:00
telephony Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
thermal thermal: Add event notification to thermal framework 2011-01-12 00:08:35 -05:00
timers tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
trace Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
uml Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
usb USB: use the runtime-PM autosuspend implementation 2010-11-16 14:03:41 -08:00
video4linux [media] cardlist: Update lists for em28xx and saa7134 2010-12-29 08:17:17 -02:00
vm thp: transparent hugepage support documentation 2011-01-13 17:32:38 -08:00
w1 w1: DS2423 counter driver and documentation 2011-01-13 08:03:22 -08:00
watchdog watchdog: docs: add an entry for imx2_wdt 2010-07-01 16:02:55 +00:00
wimax
x86 x86: support XZ-compressed kernel 2011-01-13 08:03:25 -08:00
zh_CN Docs/Kconfig: Update: osdl.org -> linuxfoundation.org 2010-11-15 23:50:13 +01:00
.gitignore add random binaries to .gitignore 2010-04-08 11:34:34 +02:00
00-INDEX mmc: add erase, secure erase, trim and secure trim operations 2010-08-12 08:43:30 -07:00
apparmor.txt AppArmor: update Maintainer and Documentation 2010-08-02 15:35:15 +10:00
applying-patches.txt
atomic_ops.txt Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
bad_memory.txt
basic_profiling.txt
binfmt_misc.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
braille-console.txt trivial: Miscellaneous documentation typo fixes 2009-06-12 18:01:47 +02:00
bt8xxgpio.txt
btmrvl.txt Bluetooth: Add documentation for Marvell Bluetooth driver 2009-08-22 14:25:32 -07:00
BUG-HUNTING
bus-virt-phys-mapping.txt documentation: fix almost duplicate filenames (IO/io-mapping.txt) 2010-07-20 17:49:30 +00:00
cachetlb.txt Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
Changes Documentation update broken web addresses 2010-07-11 21:55:42 +02:00
circular-buffers.txt Document Linux's circular buffering capabilities 2010-03-24 16:31:22 -07:00
coccinelle.txt scripts/coccinelle: update for compatability with Coccinelle 0.2.4 2010-12-03 12:27:01 +01:00
CodingStyle trivial: fix typo milisecond/millisecond for documentation and source comments. 2009-06-12 18:01:46 +02:00
cpu-hotplug.txt documentation: fix erroneous email address. 2010-08-11 23:04:10 +09:30
cpu-load.txt
cputopology.txt topology/sysfs: Provide book id and siblings attributes 2010-09-09 20:41:25 +02:00
credentials.txt CRED: Fix __task_cred()'s lockdep check and banner comment 2010-07-29 15:16:18 -07:00
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt ieee1394: update URLs in debugging-via-ohci1394.txt 2009-10-03 09:28:11 +02:00
dell_rbu.txt trivial: Documentation/dell_rbu.txt: fix typos 2009-06-12 18:01:50 +02:00
devices.txt Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2010-10-28 09:35:11 -07:00
DMA-API-HOWTO.txt Documentation: DMA-API-HOWTO.txt: rename ARCH_KMALLOC_MINALIGN to ARCH_DMA_MINALIGN 2010-08-14 11:56:46 -07:00
DMA-API.txt dma-mapping: remove dma_is_consistent API 2010-08-11 08:59:21 -07:00
DMA-attributes.txt
DMA-ISA-LPC.txt
dmaengine.txt
dontdiff Documentation/dontdiff: add further autogenerated files to ignore list 2011-01-06 09:59:37 -08:00
dynamic-debug-howto.txt Dynamic Debug: Introduce ddebug_query= boot parameter 2010-10-22 10:16:42 -07:00
edac.txt EDAC: Fix typos in Documentation/edac.txt 2010-11-25 17:32:47 +01:00
eisa.txt doc: fix Defaultd -> Defaults typo in EISA doc 2010-02-05 12:22:39 +01:00
email-clients.txt Documentation/email-clients.txt: update Thunderbird docs with wordwrap plugin 2011-01-13 08:03:15 -08:00
feature-removal-schedule.txt Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2011-01-13 20:15:35 -08:00
flexible-arrays.txt Update flex_arrays.txt 2009-10-15 07:25:20 -06:00
futex-requeue-pi.txt futex: add requeue-pi documentation 2009-05-09 07:12:50 +02:00
gcov.txt trivial: fix typo in CONFIG_DEBUG_FS in gcov doc 2009-09-21 15:14:56 +02:00
gpio.txt Revert "gpiolib: annotate gpio-intialization with __must_check" 2011-01-13 17:26:46 -08:00
highuid.txt
HOWTO Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
hw_random.txt
init.txt init/main.c: improve usability in case of init binary failure 2010-03-06 11:26:29 -08:00
initrd.txt
intel_txt.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
Intel-IOMMU.txt intel-iommu: Kill DMAR_BROKEN_GFX_WA option. 2009-09-19 09:37:23 -07:00
io_ordering.txt
io-mapping.txt
iostats.txt remove extraneous 'is' from Documentation/iostats.txt 2011-01-03 14:00:28 +01:00
IPMI.txt IPMI: Add the document description of ipmi_get_smi_info 2010-12-14 00:22:00 -05:00
IRQ-affinity.txt
IRQ.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt docbook: warn on unused doc entries 2010-09-11 16:49:21 -07:00
kernel-docs.txt Documentation: update kernel-docs.txt 2011-01-06 09:59:38 -08:00
kernel-parameters.txt Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2011-01-13 20:15:35 -08:00
keys-request-key.txt
keys-trusted-encrypted.txt keys: add new trusted key-type 2010-11-29 08:55:25 +11:00
keys.txt KEYS: Add a keyctl to install a process's session keyring on its parent [try #6] 2009-09-02 21:29:22 +10:00
kmemcheck.txt kmemcheck: update documentation 2009-07-01 22:36:22 +02:00
kmemleak.txt kmemleak: add clear command support 2009-09-08 16:36:08 +01:00
kobject.txt kobject: documentation: Update to refer to kset-example.c. 2010-03-19 07:12:20 -07:00
kprobes.txt tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
kref.txt kref: double kref_put() in my_data_handler() 2009-09-18 09:48:52 -07:00
ldm.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
leds-class.txt led-class: always implement blinking 2010-11-12 07:55:32 -08:00
leds-lp3944.txt leds: LED driver for National Semiconductor LP3944 Funlight Chip 2009-06-23 20:21:38 +01:00
local_ops.txt trivial: Miscellaneous documentation typo fixes 2009-06-12 18:01:47 +02:00
lockdep-design.txt lockdep: Fix typos in documentation 2009-08-07 12:03:46 +02:00
lockstat.txt lockstat: Add usage info to Documentation/lockstat.txt 2009-12-06 13:20:02 +01:00
logo.gif Revert "linux.conf.au 2009: Tuz" 2009-04-27 12:00:27 -07:00
logo.txt Revert "linux.conf.au 2009: Tuz" 2009-04-27 12:00:27 -07:00
magic-number.txt take coda-private headers out of include/linux 2011-01-12 20:02:48 -05:00
Makefile [media] Remove the old V4L1 v4lgrab.c file 2010-12-29 08:17:12 -02:00
ManagementStyle
mca.txt
md.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
memory-barriers.txt Document Linux's circular buffering capabilities 2010-03-24 16:31:22 -07:00
memory-hotplug.txt mm: add numa node symlink for memory section in sysfs 2009-12-15 08:53:17 -08:00
memory.txt Documentation/memory.txt: remove some very outdated recommendations 2009-09-22 07:17:26 -07:00
mono.txt
mutex-design.txt mutex: Fix annotations to include it in kernel-locking docbook 2010-09-03 08:19:51 +02:00
nmi_watchdog.txt
nommu-mmap.txt nommu: fix malloc performance by adding uninitialized flag 2009-12-15 08:53:24 -08:00
numastat.txt mm: fix NUMA accounting in numastat.txt 2009-09-22 07:17:39 -07:00
oops-tracing.txt panic: Add taint flag TAINT_FIRMWARE_WORKAROUND ('I') 2010-05-19 08:37:43 +01:00
padata.txt Documentation/padata.txt: fix typos etc. 2010-08-11 08:59:18 -07:00
parport-lowlevel.txt
parport.txt
pi-futex.txt
pnp.txt doc: capitalization and other minor fixes in pnp doc 2010-02-05 12:22:44 +01:00
preempt-locking.txt
printk-formats.txt
prio_tree.txt
rbtree.txt Documentation: remove anticipatory scheduler info 2010-11-11 12:09:59 +01:00
rfkill.txt Document the rfkill sysfs ABI 2010-03-10 17:09:33 -05:00
robust-futex-ABI.txt futex: documentation: fix inconsistent description of futex list_op_pending 2009-06-18 13:03:56 -07:00
robust-futexes.txt
rt-mutex-design.txt variable name fix to Documentation/rt-mutex-design.txt 2010-06-05 17:39:09 +02:00
rt-mutex.txt
rtc.txt rtc: add boot_timesource sysfs attribute 2009-09-23 07:39:46 -07:00
SAK.txt
SecurityBugs
SELinux.txt
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
SM501.txt trivial: Miscellaneous documentation typo fixes 2009-06-12 18:01:47 +02:00
Smack.txt Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
sparse.txt update email address 2010-07-19 10:56:54 +02:00
spinlocks.txt Documentation: rw_lock lessons learned 2009-12-14 09:46:56 -08:00
stable_api_nonsense.txt
stable_kernel_rules.txt Documentation: -stable rules: upstream commit ID requirement reworded 2010-04-22 15:24:56 -07:00
SubmitChecklist Documentation: update SubmitChecklist for O=objdir and kconfig testing 2010-05-24 07:31:20 -07:00
SubmittingDrivers Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
SubmittingPatches SubmittingPatches: add more about patch descriptions 2010-08-09 20:45:05 -07:00
svga.txt
sysfs-rules.txt Fix typos in comments 2010-03-16 11:47:56 +01:00
sysrq.txt documentation: update sysrq.txt magic sysrq keys 2010-10-26 17:32:41 -07:00
tomoyo.txt TOMOYO: Update version to 2.3.0 2010-08-02 15:35:10 +10:00
unaligned-memory-access.txt
unicode.txt
unshare.txt
VGA-softcursor.txt
vgaarbiter.txt vgaarbiter: fix a typo in the vgaarbiter Documentation 2009-12-16 11:28:58 -08:00
video-output.txt
volatile-considered-harmful.txt Documentation/volatile-considered-harmful.txt: correct cpu_relax() documentation 2010-03-24 16:31:20 -07:00
workqueue.txt workqueue: add and use WQ_MEM_RECLAIM flag 2010-10-11 15:20:26 +02:00
xz.txt decompressors: add XZ decompressor module 2011-01-13 08:03:24 -08:00
zorro.txt