This fixed a case that 'sparse' spotted where hpfs_setattr has an error return
that didn't go through it's path that unlocks.
This is against git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
version 6313e3c217.
Build tested only, I don't have an hpfs file system to test.
Dave
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
f_flags and f_spare fields were not copied to userspace when
compat_sys_[f]statfs64 called.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The commit 7ed1ee6118 ("Take statfs variants to fs/statfs.c")
separates out statfs syscalls from fs/open.c. Thus the comment
should be changed also.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Jiri Kosina <trivial@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
*@ret_pointer is initialized to @fast_pointer thus the assignment is
redundant.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
- Fix a kconfig unmet dependency warning.
- Remove the comment that identifies which filesystems use POSIX ACL
utility routines.
- Move the FS_POSIX_ACL symbol outside of the BLOCK symbol if/endif block
because its functions do not depend on BLOCK and some of the filesystems
that use it do not depend on BLOCK.
warning: (GENERIC_ACL && JFFS2_FS_POSIX_ACL && NFSD_V4 && NFS_ACL_SUPPORT && 9P_FS_POSIX_ACL) selects FS_POSIX_ACL which has unmet direct dependencies (BLOCK)
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There's an unlikely() in fget_light() that assumes the file ref count
will be 1. Running the annotate branch profiler on a desktop that is
performing daily tasks (running firefox, evolution, xchat and is also part
of a distcc farm), it shows that the ref count is not 1 that often.
correct incorrect % Function File Line
------- --------- - -------- ---- ----
1035099358 6209599193 85 fget_light file_table.c 315
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In fput_light(), there's an unlikely(fput_needed), which running on
my normal desktop doing firefox, xchat, evolution and part of my distcc farm,
and running the annotate branch profiler shows that the unlikely is not
very unlikely.
correct incorrect % Function File Line
------- --------- - -------- ---- ----
0 48 100 fput_light file.h 26
115828710 897415279 88 fput_light file.h 26
865271179 5286128445 85 fput_light file.h 26
19568539 8923664 31 fput_light file.h 26
12353677 3562279 22 fput_light file.h 26
267691 67062 20 fput_light file.h 26
15014853 348172 2 fput_light file.h 26
209258 205 0 fput_light file.h 26
1364164 0 0 fput_light file.h 26
Which gives 1032903812 times it was correct and 6203351846 times it was
incorrect, or 85% incorrect.
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently all filesystems except XFS implement fallocate asynchronously,
while XFS forced a commit. Both of these are suboptimal - in case of O_SYNC
I/O we really want our allocation on disk, especially for the !KEEP_SIZE
case where we actually grow the file with user-visible zeroes. On the
other hand always commiting the transaction is a bad idea for fast-path
uses of fallocate like for example in recent Samba versions. Given
that block allocation is a data plane operation anyway change it from
an inode operation to a file operation so that we have the file structure
available that lets us check for O_SYNC.
This also includes moving the code around for a few of the filesystems,
and remove the already unnedded S_ISDIR checks given that we only wire
up fallocate for regular files.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Instead of various home grown checks that might need updates for new
flags just check for any bit outside the mask of the features supported
by the filesystem. This makes the check future proof for any newly
added flag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Building error for smbfs:
drivers/staging/smbfs/dir.c:286: error: static declaration of 'smbfs_dentry_operations' follows non-static declaration
drivers/staging/smbfs/proto.h:42: error: previous declaration of 'smbfs_dentry_operations' was here
drivers/staging/smbfs/dir.c:294: error: static declaration of 'smbfs_dentry_operations_case' follows non-static declaration
drivers/staging/smbfs/proto.h:41: error: previous declaration of 'smbfs_dentry_operations_case' was here
make[3]: *** [drivers/staging/smbfs/dir.o] Error 1
make[2]: *** [drivers/staging/smbfs] Error 2
make[1]: *** [drivers/staging] Error 2
make[1]: *** Waiting for unfinished jobs....
Fix it by removing static keywords
Signed-off-by: Yang Ruirui <ruirui.r.yang@tieto.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
do_add_mount() and mnt_clear_expiry() are not needed outside of
namespace.c anymore, now that namei has finish_automount() to
use.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
That gets rid of the kludge in finish_automount() - we need
to keep refcount on the vfsmount as-is until we evict it from
expiry list.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Fix these:
drivers/nfc/pn544.c: In function 'pn544_read':
drivers/nfc/pn544.c:356: warning: comparison of distinct pointer types lacks a cast
drivers/nfc/pn544.c:377: warning: comparison of distinct pointer types lacks a cast
drivers/nfc/pn544.c: In function 'pn544_write':
drivers/nfc/pn544.c:463: warning: comparison of distinct pointer types lacks a cast
drivers/nfc/pn544.c:485: warning: comparison of distinct pointer types lacks a cast
Cc: "Matti J. Aaltonen" <matti.j.aaltonen@nokia.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On PARISC, we have an include of linux/mm.h inside our asm/pgtable.h, so
this patch
commit 14fd403f21
Author: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu Jan 13 15:46:37 2011 -0800
thp: export maybe_mkwrite
causes us an unsatisfiable use of pte_mkwrite in linux/mm.h.
The fix is to avoid including linux/mm.h in our pgtable.h, which
unbreaks the build.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pmdp_get_and_clear/pmdp_clear_flush/pmdp_splitting_flush were trapped as
BUG() and they were defined only to diminish the risk of build issues on
not-x86 archs and to be consistent with the generic pte methods previously
defined in include/asm-generic/pgtable.h.
But they are causing more trouble than they were supposed to solve, so
it's simpler not to define them when THP is off.
This is also correcting the export of pmdp_splitting_flush which is
currently unused (x86 isn't using the generic implementation in
mm/pgtable-generic.c and no other arch needs that [yet]).
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Sam Ravnborg <sam@ravnborg.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mnt_longterm is there only on SMP
Reported-and-tested-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch fixes the following kconfig error after changing
CONFIGFS_FS -> select SYSFS:
fs/sysfs/Kconfig:1:error: recursive dependency detected!
fs/sysfs/Kconfig:1: symbol SYSFS is selected by CONFIGFS_FS
fs/configfs/Kconfig:1: symbol CONFIGFS_FS is selected by OCFS2_FS
fs/ocfs2/Kconfig:1: symbol OCFS2_FS depends on SYSFS
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: James Bottomley <James.Bottomley@suse.de>
This patch fixes the following kconfig error after changing
CONFIGFS_FS -> select SYSFS:
fs/sysfs/Kconfig:1:error: recursive dependency detected!
fs/sysfs/Kconfig:1: symbol SYSFS is selected by CONFIGFS_FS
fs/configfs/Kconfig:1: symbol CONFIGFS_FS is selected by DLM
fs/dlm/Kconfig:1: symbol DLM depends on SYSFS
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: James Bottomley <James.Bottomley@suse.de>
This patch fixes the following kconfig error after changing
CONFIGFS_FS -> select SYSFS:
fs/sysfs/Kconfig:1:error: recursive dependency detected!
fs/sysfs/Kconfig:1: symbol SYSFS is selected by CONFIGFS_FS
fs/configfs/Kconfig:1: symbol CONFIGFS_FS is selected by NETCONSOLE_DYNAMIC
drivers/net/Kconfig:3390: symbol NETCONSOLE_DYNAMIC depends on SYSFS
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: James Bottomley <James.Bottomley@suse.de>
This patch changes configfs to select SYSFS to fix the following:
warning: (TARGET_CORE && GFS2_FS) selects CONFIGFS_FS which has unmet direct dependencies (SYSFS)
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Acked-by: Joel Becker <jlbec@evilplan.org>
Fix the build failure in some configurations:
CC [M] fs/btrfs/ctree.o
In file included from fs/btrfs/ctree.c:21:0:
fs/btrfs/ctree.h:1003:17: error: field 'super_kobj' has incomplete type
fs/btrfs/ctree.h:1074:17: error: field 'root_kobj' has incomplete type
make[2]: *** [fs/btrfs/ctree.o] Error 1
make[1]: *** [fs/btrfs] Error 2
make: *** [fs] Error 2
caused by commit 57cc7215b7 ("headers: kobject.h redux")
We need to include kobject.h here.
Reported-by: Jeff Garzik <jeff@garzik.org>
Fix-suggested-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 415e12b237 ("PCI/ACPI: Request _OSC control once for each root
bridge (v3)") put the acpi_hest_init() call in acpi_pci_root_init() into
a wrong place, presumably because the author confused acpi_pci_disabled
with acpi_disabled. Bring the code ordering in acpi_pci_root_init()
back to sanity.
Additionally, make sure that hest_disable is set when acpi_disabled is
set, which is going to prevent acpi_hest_parse(), that still may be
executed for acpi_disabled=1 through aer_acpi_firmware_first(), from
crashing because of uninitialized hest_tab.
Reported-and-tested-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After commit 415e12b237 ("PCI/ACPI: Request _OSC control once for each
root bridge (v3)") include/linux/pci-acpi.h is included by
drivers/pci/pcie/aer/aerdrv.c and if CONFIG_ACPI is unset, the bogus and
unnecessary alternative definition of acpi_find_root_bridge_handle()
causes a build error to occur.
Remove the offending piece of garbage.
Reported-and-tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (23 commits)
sanitize vfsmount refcounting changes
fix old umount_tree() breakage
autofs4: Merge the remaining dentry ops tables
Unexport do_add_mount() and add in follow_automount(), not ->d_automount()
Allow d_manage() to be used in RCU-walk mode
Remove a further kludge from __do_follow_link()
autofs4: Bump version
autofs4: Add v4 pseudo direct mount support
autofs4: Fix wait validation
autofs4: Clean up autofs4_free_ino()
autofs4: Clean up dentry operations
autofs4: Clean up inode operations
autofs4: Remove unused code
autofs4: Add d_manage() dentry operation
autofs4: Add d_automount() dentry operation
Remove the automount through follow_link() kludge code from pathwalk
CIFS: Use d_automount() rather than abusing follow_link()
NFS: Use d_automount() rather than abusing follow_link()
AFS: Use d_automount() rather than abusing follow_link()
Add an AT_NO_AUTOMOUNT flag to suppress terminal automount
...
Instead of splitting refcount between (per-cpu) mnt_count
and (SMP-only) mnt_longrefs, make all references contribute
to mnt_count again and keep track of how many are longterm
ones.
Accounting rules for longterm count:
* 1 for each fs_struct.root.mnt
* 1 for each fs_struct.pwd.mnt
* 1 for having non-NULL ->mnt_ns
* decrement to 0 happens only under vfsmount lock exclusive
That allows nice common case for mntput() - since we can't drop the
final reference until after mnt_longterm has reached 0 due to the rules
above, mntput() can grab vfsmount lock shared and check mnt_longterm.
If it turns out to be non-zero (which is the common case), we know
that this is not the final mntput() and can just blindly decrement
percpu mnt_count. Otherwise we grab vfsmount lock exclusive and
do usual decrement-and-check of percpu mnt_count.
For fs_struct.c we have mnt_make_longterm() and mnt_make_shortterm();
namespace.c uses the latter in places where we don't already hold
vfsmount lock exclusive and opencodes a few remaining spots where
we need to manipulate mnt_longterm.
Note that we mostly revert the code outside of fs/namespace.c back
to what we used to have; in particular, normal code doesn't need
to care about two kinds of references, etc. And we get to keep
the optimization Nick's variant had bought us...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Expiry-related code calls umount_tree() several times with
the same list to collect vfsmounts to. Which is fine, except
that umount_tree() implicitly assumed that the list would
be empty on each call - it moves the victims over there and
then iterates through the list kicking them out. It's *almost*
idempotent, so everything nearly worked. However, mnt->ghosts
handling (and thus expirability checks) had been broken - that
part was not idempotent...
The fix is trivial - use local temporary list, splice it to
the the collector list when we are through.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge the remaining autofs4 dentry ops tables. It doesn't matter if
d_automount and d_manage are present on something that's not mountable or
holdable as these ops are only used if the appropriate flags are set in
dentry->d_flags.
[AV] switch to ->s_d_op, since now _everything_ on autofs4 is using the
same dentry_operations.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
added rather than calling do_add_mount() itself. follow_automount() will then
do the addition.
This slightly complicates things as ->d_automount() normally wants to add the
new vfsmount to an expiration list and start an expiration timer. The problem
with that is that the vfsmount will be deleted if it has a refcount of 1 and
the timer will not repeat if the expiration list is empty.
To this end, we require the vfsmount to be returned from d_automount() with a
refcount of (at least) 2. One of these refs will be dropped unconditionally.
In addition, follow_automount() must get a 3rd ref around the call to
do_add_mount() lest it eat a ref and return an error, leaving the mount we
have open to being expired as we would otherwise have only 1 ref on it.
d_automount() should also add the the vfsmount to the expiration list (by
calling mnt_set_expiry()) and start the expiration timer before returning, if
this mechanism is to be used. The vfsmount will be unlinked from the
expiration list by follow_automount() if do_add_mount() fails.
This patch also fixes the call to do_add_mount() for AFS to propagate the mount
flags from the parent vfsmount.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Allow d_manage() to be called from pathwalk when it is in RCU-walk mode as well
as when it is in Ref-walk mode. This permits __follow_mount_rcu() to call
d_manage() directly. d_manage() needs a parameter to indicate that it is in
RCU-walk mode as it isn't allowed to sleep if in that mode (but should return
-ECHILD instead).
autofs4_d_manage() can then be set to retain RCU-walk mode if the daemon
accesses it and otherwise request dropping back to ref-walk mode.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Remove a further kludge from __do_follow_link() as it's no longer required with
the automount code.
This reverts the non-helper-function parts of
051d381259, which breaks union mounts.
Reported-by: vaurora@redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Increase the autofs module sub-version so we can tell what kernel
implementation is being used from user space debug logging.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Version 4 of autofs provides a pseudo direct mount implementation
that relies on directories at the leaves of a directory tree under
an indirect mount to trigger mounts.
This patch adds support for that functionality.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
It is possible for the check in wait.c:validate_request() to return
an incorrect result if the dentry that was mounted upon has changed
during the callback.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
When this function is called the local reference count does't need to
be updated since the dentry is going away and dput definitely must
not be called here.
Also the autofs info struct field inode isn't used so remove it.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There are now two distinct dentry operations uses. One for dentrys
that trigger mounts and one for dentrys that do not.
Rationalize the use of these dentry operations and rename them to
reflect their function.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Since the use of ->follow_link() has been eliminated there is no
need to separate the indirect and direct inode operations.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Remove code that is not used due to the use of ->d_automount()
and ->d_manage().
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This patch required a previous patch to add the ->d_automount()
dentry operation.
Add a function to use the newly defined ->d_manage() dentry operation
for blocking during mount and expire.
Whether the VFS calls the dentry operations d_automount() and d_manage()
is controled by the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags. autofs
uses the d_automount() operation to callback to user space to request
mount operations and the d_manage() operation to block walks into mounts
that are under construction or destruction.
In order to prevent these functions from being called unnecessarily the
DMANAGED_* flags are cleared for cases which would cause this. In the
common case the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags are both
set for dentrys waiting to be mounted. The DMANAGED_TRANSIT flag is
cleared upon successful mount request completion and set during expire
runs, both during the dentry expire check, and if selected for expire,
is left set until a subsequent successful mount request completes.
The exception to this is the so-called rootless multi-mount which has
no actual mount at its base. In this case the DMANAGED_AUTOMOUNT flag
is cleared upon successful mount request completion as well and set
again after a successful expire.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a function to use the newly defined ->d_automount() dentry operation
for triggering mounts instead of doing the user space callback in ->lookup()
and ->d_revalidate().
Note, to be useful the subsequent patch to add the ->d_manage() dentry
operation is also needed so the discussion of functionality is deferred to
that patch.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Remove the automount through follow_link() kludge code from pathwalk in favour
of using d_automount().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make CIFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.
[NOTE: THIS IS UNTESTED!]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make NFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make AFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add an AT_NO_AUTOMOUNT flag to suppress terminal automounting of automount
point directories. This can be used by fstatat() users to permit the
gathering of attributes on an automount point and also prevent
mass-automounting of a directory of automount points by ls.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a dentry op (d_manage) to permit a filesystem to hold a process and make it
sleep when it tries to transit away from one of that filesystem's directories
during a pathwalk. The operation is keyed off a new dentry flag
(DCACHE_MANAGE_TRANSIT).
The filesystem is allowed to be selective about which processes it holds and
which it permits to continue on or prohibits from transiting from each flagged
directory. This will allow autofs to hold up client processes whilst letting
its userspace daemon through to maintain the directory or the stuff behind it
or mounted upon it.
The ->d_manage() dentry operation:
int (*d_manage)(struct path *path, bool mounting_here);
takes a pointer to the directory about to be transited away from and a flag
indicating whether the transit is undertaken by do_add_mount() or
do_move_mount() skipping through a pile of filesystems mounted on a mountpoint.
It should return 0 if successful and to let the process continue on its way;
-EISDIR to prohibit the caller from skipping to overmounted filesystems or
automounting, and to use this directory; or some other error code to return to
the user.
->d_manage() is called with namespace_sem writelocked if mounting_here is true
and no other locks held, so it may sleep. However, if mounting_here is true,
it may not initiate or wait for a mount or unmount upon the parameter
directory, even if the act is actually performed by userspace.
Within fs/namei.c, follow_managed() is extended to check with d_manage() first
on each managed directory, before transiting away from it or attempting to
automount upon it.
follow_down() is renamed follow_down_one() and should only be used where the
filesystem deliberately intends to avoid management steps (e.g. autofs).
A new follow_down() is added that incorporates the loop done by all other
callers of follow_down() (do_add/move_mount(), autofs and NFSD; whilst AFS, NFS
and CIFS do use it, their use is removed by converting them to use
d_automount()). The new follow_down() calls d_manage() as appropriate. It
also takes an extra parameter to indicate if it is being called from mount code
(with namespace_sem writelocked) which it passes to d_manage(). follow_down()
ignores automount points so that it can be used to mount on them.
__follow_mount_rcu() is made to abort rcu-walk mode if it hits a directory with
DCACHE_MANAGE_TRANSIT set on the basis that we're probably going to have to
sleep. It would be possible to enter d_manage() in rcu-walk mode too, and have
that determine whether to abort or not itself. That would allow the autofs
daemon to continue on in rcu-walk mode.
Note that DCACHE_MANAGE_TRANSIT on a directory should be cleared when it isn't
required as every tranist from that directory will cause d_manage() to be
invoked. It can always be set again when necessary.
==========================
WHAT THIS MEANS FOR AUTOFS
==========================
Autofs currently uses the lookup() inode op and the d_revalidate() dentry op to
trigger the automounting of indirect mounts, and both of these can be called
with i_mutex held.
autofs knows that the i_mutex will be held by the caller in lookup(), and so
can drop it before invoking the daemon - but this isn't so for d_revalidate(),
since the lock is only held on _some_ of the code paths that call it. This
means that autofs can't risk dropping i_mutex from its d_revalidate() function
before it calls the daemon.
The bug could manifest itself as, for example, a process that's trying to
validate an automount dentry that gets made to wait because that dentry is
expired and needs cleaning up:
mkdir S ffffffff8014e05a 0 32580 24956
Call Trace:
[<ffffffff885371fd>] :autofs4:autofs4_wait+0x674/0x897
[<ffffffff80127f7d>] avc_has_perm+0x46/0x58
[<ffffffff8009fdcf>] autoremove_wake_function+0x0/0x2e
[<ffffffff88537be6>] :autofs4:autofs4_expire_wait+0x41/0x6b
[<ffffffff88535cfc>] :autofs4:autofs4_revalidate+0x91/0x149
[<ffffffff80036d96>] __lookup_hash+0xa0/0x12f
[<ffffffff80057a2f>] lookup_create+0x46/0x80
[<ffffffff800e6e31>] sys_mkdirat+0x56/0xe4
versus the automount daemon which wants to remove that dentry, but can't
because the normal process is holding the i_mutex lock:
automount D ffffffff8014e05a 0 32581 1 32561
Call Trace:
[<ffffffff80063c3f>] __mutex_lock_slowpath+0x60/0x9b
[<ffffffff8000ccf1>] do_path_lookup+0x2ca/0x2f1
[<ffffffff80063c89>] .text.lock.mutex+0xf/0x14
[<ffffffff800e6d55>] do_rmdir+0x77/0xde
[<ffffffff8005d229>] tracesys+0x71/0xe0
[<ffffffff8005d28d>] tracesys+0xd5/0xe0
which means that the system is deadlocked.
This patch allows autofs to hold up normal processes whilst the daemon goes
ahead and does things to the dentry tree behind the automouter point without
risking a deadlock as almost no locks are held in d_manage() and none in
d_automount().
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>
