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* autofs: set things up *before* registering fs typeAl Viro2012-03-201-3/+3
| | | | | | | it's not a serious race, but we really want misc device before anybody gets to mount this sucker. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch open-coded instances of d_make_root() to new helperAl Viro2012-03-201-8/+2
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs: work around unhappy compat problem on x86-64Ian Kent2012-02-254-3/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the autofs protocol version 5 packet type was added in commit 5c0a32fc2cd0 ("autofs4: add new packet type for v5 communications"), it obvously tried quite hard to be word-size agnostic, and uses explicitly sized fields that are all correctly aligned. However, with the final "char name[NAME_MAX+1]" array at the end, the actual size of the structure ends up being not very well defined: because the struct isn't marked 'packed', doing a "sizeof()" on it will align the size of the struct up to the biggest alignment of the members it has. And despite all the members being the same, the alignment of them is different: a "__u64" has 4-byte alignment on x86-32, but native 8-byte alignment on x86-64. And while 'NAME_MAX+1' ends up being a nice round number (256), the name[] array starts out a 4-byte aligned. End result: the "packed" size of the structure is 300 bytes: 4-byte, but not 8-byte aligned. As a result, despite all the fields being in the same place on all architectures, sizeof() will round up that size to 304 bytes on architectures that have 8-byte alignment for u64. Note that this is *not* a problem for 32-bit compat mode on POWER, since there __u64 is 8-byte aligned even in 32-bit mode. But on x86, 32-bit and 64-bit alignment is different for 64-bit entities, and as a result the structure that has exactly the same layout has different sizes. So on x86-64, but no other architecture, we will just subtract 4 from the size of the structure when running in a compat task. That way we will write the properly sized packet that user mode expects. Not pretty. Sadly, this very subtle, and unnecessary, size difference has been encoded in user space that wants to read packets of *exactly* the right size, and will refuse to touch anything else. Reported-and-tested-by: Thomas Meyer <thomas@m3y3r.de> Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* autofs4 - fix lockdep splat in autofsSteven Rostedt2012-02-131-0/+2
| | | | | | | | | | | When recursing down the locks when traversing a tree/list in get_next_positive_dentry() or get_next_positive_subdir() a lock can change from being nested to being a parent which breaks lockdep. This patch tells lockdep about what we did. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix deal with autofs4_write racesIan Kent2012-01-131-1/+1
| | | | | | | | | | | | | | | | | | | I don't know how I missed this obvious mistake when I reviewed Als' patches, sorry. [ Quoting Al: Grr... Note to self: do git status *and* git stash show -p before git push. Nothing like "WTF? I'd fixed that braino" feeling ;-/ Al sent the same patch - it got broken in commit d668dc56631d: "autofs4: deal with autofs4_write/autofs4_write races". ] Reported-and-tested-by: Dave Airlie <airlied@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* autofs4: deal with autofs4_write/autofs4_write racesAl Viro2012-01-113-4/+7
| | | | | | | | | | | Just serialize the actual writing of packets into pipe on a new mutex, independent from everything else in the locking hierarchy. As soon as something has started feeding a piece of packet into the pipe to daemon, we *want* everything else about to try the same to wait until we are done. Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: catatonic_mode vs. notify_daemon raceAl Viro2012-01-111-11/+14
| | | | | | | | | | | | | | | | | we need to hold ->wq_mutex while we are forming the packet to send, lest we have autofs4_catatonic_mode() setting wq->name.name to NULL just as autofs4_notify_daemon() decides to memcpy() from it... We do have check for catatonic mode immediately after that (under ->wq_mutex, as it ought to be) and packet won't be actually sent, but it'll be too late for us if we oops on that memcpy() from NULL... Fix is obvious - just extend the area covered by ->wq_mutex over that switch and check whether it's catatonic *before* doing anything else. Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: autofs4_wait() vs. autofs4_catatonic_mode() raceAl Viro2012-01-111-1/+7
| | | | | | | | | | | | | We need to recheck ->catatonic after autofs4_wait() got ->wq_mutex for good, or we might end up with wq inserted into queue after autofs4_catatonic_mode() had done its thing. It will stick there forever, since there won't be anything to clear its ->name.name. A bit of a complication: validate_request() drops and regains ->wq_mutex. It actually ends up the most convenient place to stick the check into... Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: switch ->show_options() to struct dentry *Al Viro2012-01-061-3/+3
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: prefer ->dentry->d_sb to ->mnt->mnt_sbAl Viro2012-01-061-5/+5
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: propagate umode_tAl Viro2012-01-032-2/+2
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch vfs_mkdir() and ->mkdir() to umode_tAl Viro2012-01-031-2/+2
| | | | | | | vfs_mkdir() gets int, but immediately drops everything that might not fit into umode_t and that's the only caller of ->mkdir()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* filesystems: add set_nlink()Miklos Szeredi2011-11-021-1/+1
| | | | | | | | | Replace remaining direct i_nlink updates with a new set_nlink() updater function. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
* autofs4: fix debug printk warning uncovered by cleanupLinus Torvalds2011-08-081-1/+1
| | | | | | | | | | | | | | | | | | | | The previous comit made the autofs4 debug printouts check types against the printout format, and uncovered this bug: fs/autofs4/waitq.c:106:2: warning: format ‘%08lx’ expects type ‘long unsigned int’, but argument 4 has type ‘autofs_wqt_t’ which is due to the insane type for wait_queue_token. That thing should be some fixed well-defined size (preferably just 'unsigned int' or 'u32') but for unexplained reasons it is randomly either 'unsigned long' or 'unsigned int' depending on the architecture. For now, cast it to 'unsigned long' for printing, the way we do elsewhere. Somebody else can try to explain the typedef mess. (There's a reason we don't support excessive use of typedefs in the kernel: it's usually just a good way of confusing yourself). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* autofs4: clean up uaotfs use of debug/info/warning printoutsLinus Torvalds2011-08-081-18/+8
| | | | | | | | | | | | | | Use 'pr_debug()' for DPRINTK, which will do the proper type checking on the arguments (without generating code) even when DEBUG isn't #defined. Also, use the standard __VA_ARGS__ for the macros, and stop the pointless abuse of 'do { xyz } while (0)' when the macro is already a perfectly well-formed single statement. Reported-by: David Howells <dhowells@redhat.com> Suggested-by: Joe Perches <joe@perches.com> Cc: Ian Kent <raven@themaw.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* autofs4: bogus dentry_unhash() added in ->unlink()Al Viro2011-05-301-2/+0
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: push dentry_unhash on rmdir into file systemsSage Weil2011-05-261-0/+2
| | | | | | | | | | | | Only a few file systems need this. Start by pushing it down into each fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs basis. This does not change behavior for any in-tree file systems. Acked-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Fix common misspellingsLucas De Marchi2011-03-311-1/+1
| | | | | | Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
* autofs4: Do not potentially dereference NULL pointer returned by fget() in ↵Jesper Juhl2011-03-241-0/+4
| | | | | | | | | | | | | | | | | autofs_dev_ioctl_setpipefd() In fs/autofs4/dev-ioctl.c::autofs_dev_ioctl_setpipefd() we call fget(), which may return NULL, but we do not explicitly test for that NULL return so we may end up dereferencing a NULL pointer - bad. When I originally submitted this patch I had chosen EBUSY as the return value to use if this happens. Ian Kent was kind enough to explain why that would most likely be wrong and why EBADF should most likely be used instead. This version of the patch uses EBADF. Signed-off-by: Jesper Juhl <jj@chaosbits.net> Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - remove autofs4_lockIan Kent2011-03-244-31/+20
| | | | | | | | | | The autofs4_lock introduced by the rcu-walk changes has unnecessarily broad scope. The locking is better handled by the per-autofs super block lookup_lock. Signed-off-by: Ian Kent <raven@themaw.net> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix d_manage() return on rcu-walkIan Kent2011-03-241-0/+2
| | | | | | | | The daemon never needs to block and, in the rcu-walk case an error return isn't used, so always return zero. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix autofs4_expire_indirect() traversalIan Kent2011-03-241-1/+51
| | | | | | | | | The vfs-scale changes changed the traversal used in autofs4_expire_indirect() from a list to a depth first tree traversal which isn't right. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix dentry leak in autofs4_expire_direct()Ian Kent2011-03-241-4/+3
| | | | | | | | | There is a missing dput() when returning from autofs4_expire_direct() when we see that the dentry is already a pending mount. Signed-off-by: Ian Kent <raven@themaw.net> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - reinstate last used update on accessIan Kent2011-03-242-34/+14
| | | | | | | | | | | | | | When direct (and offset) mounts were introduced the the last used timeout could no longer be updated in ->d_revalidate(). This is because covered direct mounts would be followed over without calling the autofs file system. As a result the definition of the busyness check for all entries was changed to be "actually busy" being an open file or working directory within the automount. But now we have a call back in the follow so the last used update on any access can be re-instated. This requires DCACHE_MANAGE_TRANSIT to always be set. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* lose 'mounting_here' argument in ->d_manage()Al Viro2011-03-181-3/+3
| | | | | | it's always false... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: clean ->d_release() and autofs4_free_ino() upAl Viro2011-01-183-19/+16
| | | | | | | | The latter is called only when both ino and dentry are about to be freed, so cleaning ->d_fsdata and ->dentry is pointless. Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: split autofs4_init_ino()Al Viro2011-01-183-26/+15
| | | | | | | | | split init_ino into new_ino and clean_ino; the former is what used to be init_ino(NULL, sbi), the latter is for cases where we passed non-NULL ino. Lose unused arguments. Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: mkdir and symlink always get a dentry that had passed lookupAl Viro2011-01-181-18/+10
| | | | | | | ... so ->d_fsdata will have been set up before we get there Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: autofs4_get_inode() doesn't need autofs_info * argument anymoreAl Viro2011-01-183-7/+5
| | | | | Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: kill ->size in autofs_infoAl Viro2011-01-183-6/+3
| | | | | | | | | | It's used only to pass the length of symlink body to autofs4_get_inode() in autofs4_dir_symlink(). We can bloody well set inode->i_size in autofs4_dir_symlink() directly and be done with that. Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: pass mode to autofs4_get_inode() explicitlyAl Viro2011-01-183-16/+15
| | | | | | | | | In all cases we'd set inf->mode to know value just before passing it to autofs4_get_inode(). That kills the need to store it in autofs_info and pass it to autofs_init_ino() Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: autofs4_mkroot() is not different from autofs4_init_ino()Al Viro2011-01-181-12/+1
| | | | | | | | Kill it. Mind you, it's been an obfuscated call of autofs4_init_ino() ever since 2.3.99pre6-4... Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: keep symlink body in inode->i_privateAl Viro2011-01-184-28/+9
| | | | | | | | gets rid of all ->free()/->u.symlink machinery in autofs; we simply keep symlink bodies in inode->i_private and free them in ->evict_inode(). Acked-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix debug print in autofs4_lookup()Ian Kent2011-01-181-1/+2
| | | | | | | oz_mode isn't defined any more, use autofs4_oz_mode(sbi) instead. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4 - fix get_next_positive_dentry()Ian Kent2011-01-181-2/+2
| | | | | | | | | | | | | | The initialization condition in fs/autofs4/expire.c:get_next_positive_dentry() appears to be incorrect. If prev == NULL I believe that root should be returned. Further down, at the current dentry check for it being simple_positive() it looks like the d_lock for dentry p should be dropped instead of dentry ret, otherwise when p is assinged to ret we end up with no lock on p and a lost lock on ret, which leads to a deadlock. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* autofs4: Merge the remaining dentry ops tablesDavid Howells2011-01-153-20/+4
| | | | | | | | | | | | | 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>
* Allow d_manage() to be used in RCU-walk modeDavid Howells2011-01-151-2/+6
| | | | | | | | | | | | | | 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>
* autofs4: Add v4 pseudo direct mount supportIan Kent2011-01-151-0/+58
| | | | | | | | | | | | 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>
* autofs4: Fix wait validationIan Kent2011-01-151-1/+16
| | | | | | | | | | 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>
* autofs4: Clean up autofs4_free_ino()Ian Kent2011-01-152-22/+0
| | | | | | | | | | | | 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>
* autofs4: Clean up dentry operationsIan Kent2011-01-153-29/+26
| | | | | | | | | | | | 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>
* autofs4: Clean up inode operationsIan Kent2011-01-153-21/+1
| | | | | | | | | 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>
* autofs4: Remove unused codeIan Kent2011-01-152-250/+0
| | | | | | | | | 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>
* autofs4: Add d_manage() dentry operationIan Kent2011-01-154-40/+159
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* autofs4: Add d_automount() dentry operationIan Kent2011-01-154-112/+189
| | | | | | | | | | | | | | 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>
* Add a dentry op to allow processes to be held during pathwalk transitDavid Howells2011-01-154-21/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* fs: rcu-walk aware d_revalidate methodNick Piggin2011-01-071-3/+10
| | | | | | | | Require filesystems be aware of .d_revalidate being called in rcu-walk mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning -ECHILD from all implementations. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce branches in lookup pathNick Piggin2011-01-072-6/+6
| | | | | | | | | | | | | | Reduce some branches and memory accesses in dcache lookup by adding dentry flags to indicate common d_ops are set, rather than having to check them. This saves a pointer memory access (dentry->d_op) in common path lookup situations, and saves another pointer load and branch in cases where we have d_op but not the particular operation. Patched with: git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache remove d_mountedNick Piggin2011-01-071-2/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rather than keep a d_mounted count in the dentry, set a dentry flag instead. The flag can be cleared by checking the hash table to see if there are any mounts left, which is not time critical because it is performed at detach time. The mounted state of a dentry is only used to speculatively take a look in the mount hash table if it is set -- before following the mount, vfsmount lock is taken and mount re-checked without races. This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I might use later (and some configs have larger than 32-bit spinlocks which might make use of the hole). Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>: In autofs4, when expring direct (or offset) mounts we need to ensure that we block user path walks into the autofs mount, which is covered by another mount. To do this we clear the mounted status so that follows stop before walking into the mount and are essentially blocked until the expire is completed. The automount daemon still finds the correct dentry for the umount due to the follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as an inode operation for direct and offset mounts only and is called following the lookup that stopped at the covered mount. At the end of the expire the covering mount probably has gone away so the mounted status need not be restored. But we need to check this and only restore the mounted status if the expire failed. XXX: autofs may not work right if we have other mounts go over the top of it? Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache remove dcache_lockNick Piggin2011-01-074-29/+35
| | | | | | dcache_lock no longer protects anything. remove it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
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