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2012-12-20vfs: d_obtain_alias() needs to use "/" as default name.NeilBrown
NFS appears to use d_obtain_alias() to create the root dentry rather than d_make_root. This can cause 'prepend_path()' to complain that the root has a weird name if an NFS filesystem is lazily unmounted. e.g. if "/mnt" is an NFS mount then { cd /mnt; umount -l /mnt ; ls -l /proc/self/cwd; } will cause a WARN message like WARNING: at /home/git/linux/fs/dcache.c:2624 prepend_path+0x1d7/0x1e0() ... Root dentry has weird name <> to appear in kernel logs. So change d_obtain_alias() to use "/" rather than "" as the anonymous name. Signed-off-by: NeilBrown <neilb@suse.de> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-12-20vfs: remove DCACHE_NEED_LOOKUPJeff Layton
The code that relied on that flag was ripped out of btrfs quite some time ago, and never added back. Josef indicated that he was going to take a different approach to the problem in btrfs, and that we could just eliminate this flag. Cc: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-10-02Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs update from Al Viro: - big one - consolidation of descriptor-related logics; almost all of that is moved to fs/file.c (BTW, I'm seriously tempted to rename the result to fd.c. As it is, we have a situation when file_table.c is about handling of struct file and file.c is about handling of descriptor tables; the reasons are historical - file_table.c used to be about a static array of struct file we used to have way back). A lot of stray ends got cleaned up and converted to saner primitives, disgusting mess in android/binder.c is still disgusting, but at least doesn't poke so much in descriptor table guts anymore. A bunch of relatively minor races got fixed in process, plus an ext4 struct file leak. - related thing - fget_light() partially unuglified; see fdget() in there (and yes, it generates the code as good as we used to have). - also related - bits of Cyrill's procfs stuff that got entangled into that work; _not_ all of it, just the initial move to fs/proc/fd.c and switch of fdinfo to seq_file. - Alex's fs/coredump.c spiltoff - the same story, had been easier to take that commit than mess with conflicts. The rest is a separate pile, this was just a mechanical code movement. - a few misc patches all over the place. Not all for this cycle, there'll be more (and quite a few currently sit in akpm's tree)." Fix up trivial conflicts in the android binder driver, and some fairly simple conflicts due to two different changes to the sock_alloc_file() interface ("take descriptor handling from sock_alloc_file() to callers" vs "net: Providing protocol type via system.sockprotoname xattr of /proc/PID/fd entries" adding a dentry name to the socket) * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (72 commits) MAX_LFS_FILESIZE should be a loff_t compat: fs: Generic compat_sys_sendfile implementation fs: push rcu_barrier() from deactivate_locked_super() to filesystems btrfs: reada_extent doesn't need kref for refcount coredump: move core dump functionality into its own file coredump: prevent double-free on an error path in core dumper usb/gadget: fix misannotations fcntl: fix misannotations ceph: don't abuse d_delete() on failure exits hypfs: ->d_parent is never NULL or negative vfs: delete surplus inode NULL check switch simple cases of fget_light to fdget new helpers: fdget()/fdput() switch o2hb_region_dev_write() to fget_light() proc_map_files_readdir(): don't bother with grabbing files make get_file() return its argument vhost_set_vring(): turn pollstart/pollstop into bool switch prctl_set_mm_exe_file() to fget_light() switch xfs_find_handle() to fget_light() switch xfs_swapext() to fget_light() ...
2012-09-29vfs: dcache: fix deadlock in tree traversalMiklos Szeredi
IBM reported a deadlock in select_parent(). This was found to be caused by taking rename_lock when already locked when restarting the tree traversal. There are two cases when the traversal needs to be restarted: 1) concurrent d_move(); this can only happen when not already locked, since taking rename_lock protects against concurrent d_move(). 2) racing with final d_put() on child just at the moment of ascending to parent; rename_lock doesn't protect against this rare race, so it can happen when already locked. Because of case 2, we need to be able to handle restarting the traversal when rename_lock is already held. This patch fixes all three callers of try_to_ascend(). IBM reported that the deadlock is gone with this patch. [ I rewrote the patch to be smaller and just do the "goto again" if the lock was already held, but credit goes to Miklos for the real work. - Linus ] Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-09-27trivial select_parent documentation fixJ. Bruce Fields
"Search list for X" sounds like you're trying to find X on a list. Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-09-26vfs: delete surplus inode NULL checkAlan Cox
Each iteration of d_delete we reload inode from dentry->d_inode and then call S_ISDIR(inode-i_mode), so inode cannot possibly be NULL shortly afterwards unless something went horribly wrong. Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-09-18vfs: dcache: use DCACHE_DENTRY_KILLED instead of DCACHE_DISCONNECTED in d_kill()Miklos Szeredi
IBM reported a soft lockup after applying the fix for the rename_lock deadlock. Commit c83ce989cb5f ("VFS: Fix the nfs sillyrename regression in kernel 2.6.38") was found to be the culprit. The nfs sillyrename fix used DCACHE_DISCONNECTED to indicate that the dentry was killed. This flag can be set on non-killed dentries too, which results in infinite retries when trying to traverse the dentry tree. This patch introduces a separate flag: DCACHE_DENTRY_KILLED, which is only set in d_kill() and makes try_to_ascend() test only this flag. IBM reported successful test results with this patch. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-14__d_unalias() should refuse to move mountpointsAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14vfs: switch i_dentry/d_alias to hlistAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14get rid of ->mnt_longtermAl Viro
it's enough to set ->mnt_ns of internal vfsmounts to something distinct from all struct mnt_namespace out there; then we can just use the check for ->mnt_ns != NULL in the fast path of mntput_no_expire() Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-08Revert "vfs: stop d_splice_alias creating directory aliases"Linus Torvalds
This reverts commit 7732a557b1342c6e6966efb5f07effcf99f56167 (and commit 3f50fff4dace23d3cfeb195d5cd4ee813cee68b7, which was a follow-up cleanup). We're chasing an elusive bug that Dave Jones can apparently reproduce using his system call fuzzer tool, and that looks like some kind of locking ordering problem on the directory i_mutex chain. Our i_mutex locking is rather complex, and depends on the topological ordering of the directories, which is why we have been very wary of splicing directory entries around. Of course, we really don't want to ever see aliased unconnected directories anyway, so none of this should ever happen, but this revert aims to basically get us back to a known older state. Bruce points to some of the previous discussion at http://marc.info/?i=<20110310105821.GE22723@ZenIV.linux.org.uk> and in particular a long post from Neil: http://marc.info/?i=<20110311150749.2fa2be66@notabene.brown> It should be noted that it's possible that Dave's problems come from other changes altohgether, including possibly just the fact that Dave constantly is teachning his fuzzer new tricks. So what appears to be a new bug could in fact be an old one that just gets newly triggered, but reverting these patches as "still under heavy discussion" is the right thing regardless. Requested-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: J. Bruce Fields <bfields@fieldses.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-30vfs: remove unused __d_splice_alias argumentJ. Bruce Fields
Nobody sets want_disconn any more. Reported-by: Peng Tao <bergwolf@gmail.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-30vfs: stop d_splice_alias creating directory aliasesJ. Bruce Fields
A directory should never have more than one dentry pointing to it. But d_splice_alias() will add one if it finds a directory with an already-existing non-DISCONNECTED dentry. I can't find an obvious reproducer, but I also can't see what prevents d_splice_alias() from encountering such a case. It therefore seems safest to allow d_splice_alias to use any dentry it finds. (Prior to the removal of dentry_unhash() from vfs_rmdir(), around v3.0, this could cause an nfsd deadlock like this: - Somebody attempts to remove a non-empty directory. - The dentry_unhash() in vfs_rmdir() unhashes the dentry pointing to the non-empty directory. - ->rmdir() then fails with -ENOTEMPTY - Before the vfs_rmdir() caller reaches dput(), an nfsd process in rename looks up the directory by filehandle; at the end of that lookup, this dentry is found by d_alloc_anon(), and a reference is taken on it, preventing dput() from removing it. - A regular lookup of the directory calls d_splice_alias(), finds only an unhashed (not a DISCONNECTED) dentry, and insteads adds a new one, so the directory now has two dentries. - The nfsd process in rename, which was previously looking up the source directory of the rename, now looks up the target directory (which is the same), and gets the dentry newly created by the previous lookup. - The rename, seeing two different dentries, assumes this is a cross-directory rename and attempts to take the i_mutex on the directory twice. That reproducer no longer exists, but I don't think there was anything fundamentally incorrect about the vfs_rmdir() behavior there, so I think the real fault was here in d_splice_alias().) Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-29brlocks/lglocks: API cleanupsAndi Kleen
lglocks and brlocks are currently generated with some complicated macros in lglock.h. But there's no reason to not just use common utility functions and put all the data into a common data structure. In preparation, this patch changes the API to look more like normal function calls with pointers, not magic macros. The patch is rather large because I move over all users in one go to keep it bisectable. This impacts the VFS somewhat in terms of lines changed. But no actual behaviour change. [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-24mm: add a low limit to alloc_large_system_hashTim Bird
UDP stack needs a minimum hash size value for proper operation and also uses alloc_large_system_hash() for proper NUMA distribution of its hash tables and automatic sizing depending on available system memory. On some low memory situations, udp_table_init() must ignore the alloc_large_system_hash() result and reallocs a bigger memory area. As we cannot easily free old hash table, we leak it and kmemleak can issue a warning. This patch adds a low limit parameter to alloc_large_system_hash() to solve this problem. We then specify UDP_HTABLE_SIZE_MIN for UDP/UDPLite hash table allocation. Reported-by: Mark Asselstine <mark.asselstine@windriver.com> Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2012-05-21Revert "vfs: remove unnecessary d_unhashed() check from __d_lookup_rcu"Linus Torvalds
This reverts commit 8c01a529b861ba97c7d78368e6a5d4d42e946f75. It turns out the d_unhashed() check isn't unnecessary after all: while it's true that unhashing will increment the sequence numbers, that does not necessarily invalidate the RCU lookup, because it might have seen the dentry pointer (before it got unhashed), but by the time it loaded the sequence number, it could have seen the *new* sequence number (after it got unhashed). End result: we might look up an unhashed dentry that is about to be freed, with the sequence number never indicating anything bad about it. So checking that the dentry is still hashed (*after* reading the sequence number) is indeed the proper fix, and was never unnecessary. Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-21vfs: be even more careful about dentry RCU name lookupsLinus Torvalds
Miklos Szeredi points out that we need to also worry about memory odering when doing the dentry name comparison asynchronously with RCU. In particular, doing a rename can do a memcpy() of one dentry name over another, and we want to make sure that any unlocked reader will always see the proper terminating NUL character, so that it won't ever run off the allocation. Rather than having to be extra careful with the name copy or at lookup time for each character, this resolves the issue by making sure that all names that are inlined in the dentry always have a NUL character at the end of the name allocation. If we do that at dentry allocation time, we know that no future name copy will ever change that final NUL to anything else, so there are no memory ordering issues. So even if a concurrent rename ends up overwriting the NUL character that terminates the original name, we always know that there is one final NUL at the end, and there is no worry about the lockless RCU lookup traversing the name too far. The out-of-line allocations are never copied over, so we can just make sure that we write the name (with terminating NULL) and do a write barrier before we expose the name to anything else by setting it in the dentry. Reported-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Nick Piggin <npiggin@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-10vfs: make it possible to access the dentry hash/len as one 64-bit entryLinus Torvalds
This allows comparing hash and len in one operation on 64-bit architectures. Right now only __d_lookup_rcu() takes advantage of this, since that is the case we care most about. The use of anonymous struct/unions hides the alternate 64-bit approach from most users, the exception being a few cases where we initialize a 'struct qstr' with a static initializer. This makes the problematic cases use a new QSTR_INIT() helper function for that (but initializing just the name pointer with a "{ .name = xyzzy }" initializer remains valid, as does just copying another qstr structure). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-10vfs: move dentry name length comparison from dentry_cmp() into callersLinus Torvalds
All callers do want to check the dentry length, but some of them can check the length and the hash together, so doing it in dentry_cmp() can be counter-productive. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-10vfs: do the careful dentry name access for all dentry_cmp casesLinus Torvalds
Commit 12f8ad4b0533 ("vfs: clean up __d_lookup_rcu() and dentry_cmp() interfaces") did the careful ACCESS_ONCE() of the dentry name only for the word-at-a-time case, even though the issue is generic. Admittedly I don't really see gcc ever reloading the value in the middle of the loop, so the ACCESS_ONCE() protects us from a fairly theoretical issue. But better safe than sorry. Also, this consolidates the common parts of the word-at-a-time and bytewise logic, which includes checking the length. We'll be changing that later. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-10vfs: remove unnecessary d_unhashed() check from __d_lookup_rcuLinus Torvalds
The check for d_unhashed() is not strictly incorrect, but at the same time it is also not sensible. The actual dentry removal from the dentry hash chains is totally asynchronous to the __d_lookup_rcu() logic, and we depend on __d_drop() updating the sequence number to invalidate any lookup of an unhashed dentry. So checking d_unhashed() is not incorrect, but it's not useful either: the code has to work correctly even without it. So just remove it. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-04vfs: clean up __d_lookup_rcu() and dentry_cmp() interfacesLinus Torvalds
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>
2012-05-03vfs: make word-at-a-time accesses handle a non-existing pageLinus Torvalds
It turns out that there are more cases than CONFIG_DEBUG_PAGEALLOC that can have holes in the kernel address space: it seems to happen easily with Xen, and it looks like the AMD gart64 code will also punch holes dynamically. Actually hitting that case is still very unlikely, so just do the access, and take an exception and fix it up for the very unlikely case of it being a page-crosser with no next page. And hey, this abstraction might even help other architectures that have other issues with unaligned word accesses than the possible missing next page. IOW, this could do the byte order magic too. Peter Anvin fixed a thinko in the shifting for the exception case. Reported-and-tested-by: Jana Saout <jana@saout.de> Cc: Peter Anvin <hpa@zytor.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-28vfs: fix d_ancestor() case in d_materialize_uniqueMichel Lespinasse
In d_materialise_unique() there are 3 subcases to the 'aliased dentry' case; in two subcases the inode i_lock is properly released but this does not occur in the -ELOOP subcase. This seems to have been introduced by commit 1836750115f2 ("fix loop checks in d_materialise_unique()"). Signed-off-by: Michel Lespinasse <walken@google.com> Cc: stable@vger.kernel.org # v3.0+ [ Added a comment, and moved the unlock to where we generate the -ELOOP, which seems to be more natural. You probably can't actually trigger this without a buggy network file server - d_materialize_unique() is for finding aliases on non-local filesystems, and the d_ancestor() case is for a hardlinked directory loop. But we should be robust in the case of such buggy servers anyway. ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-24Merge tag 'module-for-3.4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux Pull cleanup of fs/ and lib/ users of module.h from Paul Gortmaker: "Fix up files in fs/ and lib/ dirs to only use module.h if they really need it. These are trivial in scope vs the work done previously. We now have things where any few remaining cleanups can be farmed out to arch or subsystem maintainers, and I have done so when possible. What is remaining here represents the bits that don't clearly lie within a single arch/subsystem boundary, like the fs dir and the lib dir. Some duplicate includes arising from overlapping fixes from independent subsystem maintainer submissions are also quashed." Fix up trivial conflicts due to clashes with other include file cleanups (including some due to the previous bug.h cleanup pull). * tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: lib: reduce the use of module.h wherever possible fs: reduce the use of module.h wherever possible includecheck: delete any duplicate instances of module.h
2012-03-22fs: fix kernel-doc warnings in dcache.cRandy Dunlap
Fix kernel-doc warnings in fs/dcache.c: Warning(fs/dcache.c:1743): No description found for parameter 'seqp' Warning(fs/dcache.c:1743): Excess function parameter 'seq' description in '__d_lookup_rcu' Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-21Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs pile 1 from Al Viro: "This is _not_ all; in particular, Miklos' and Jan's stuff is not there yet." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (64 commits) ext4: initialization of ext4_li_mtx needs to be done earlier debugfs-related mode_t whack-a-mole hfsplus: add an ioctl to bless files hfsplus: change finder_info to u32 hfsplus: initialise userflags qnx4: new helper - try_extent() qnx4: get rid of qnx4_bread/qnx4_getblk take removal of PF_FORKNOEXEC to flush_old_exec() trim includes in inode.c um: uml_dup_mmap() relies on ->mmap_sem being held, but activate_mm() doesn't hold it um: embed ->stub_pages[] into mmu_context gadgetfs: list_for_each_safe() misuse ocfs2: fix leaks on failure exits in module_init ecryptfs: make register_filesystem() the last potential failure exit ntfs: forgets to unregister sysctls on register_filesystem() failure logfs: missing cleanup on register_filesystem() failure jfs: mising cleanup on register_filesystem() failure make configfs_pin_fs() return root dentry on success configfs: configfs_create_dir() has parent dentry in dentry->d_parent configfs: sanitize configfs_create() ...
2012-03-20vfs: d_alloc_root() goneAl Viro
all callers converted to d_make_root() by now Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-19Merge branch 'dcache-word-accesses'Linus Torvalds
* branch 'dcache-word-accesses': vfs: use 'unsigned long' accesses for dcache name comparison and hashing This does the name hashing and lookup using word-sized accesses when that is efficient, namely on x86 (although any little-endian machine with good unaligned accesses would do). It does very much depend on little-endian logic, but it's a very hot couple of functions under some real loads, and this patch improves the performance of __d_lookup_rcu() and link_path_walk() by up to about 30%. Giving a 10% improvement on some very pathname-heavy benchmarks. Because we do make unaligned accesses past the filename, the optimization is disabled when CONFIG_DEBUG_PAGEALLOC is active, and we effectively depend on the fact that on x86 we don't really ever have the last page of usable RAM followed immediately by any IO memory (due to ACPI tables, BIOS buffer areas etc). Some of the bit operations we do are a bit "subtle". It's commented, but you do need to really think about the code. Or just consider it black magic. Thanks to people on G+ for some of the optimized bit tricks.
2012-03-19vfs: get rid of batshit-insane pointless dentry hash calculationsLinus Torvalds
For some odd historical reason, the final mixing round for the dentry cache hash table lookup had an insane "xor with big constant" logic. In two places. The big constant that is being xor'ed is GOLDEN_RATIO_PRIME, which is a fairly random-looking number that is designed to be *multiplied* with so that the bits get spread out over a whole long-word. But xor'ing with it is insane. It doesn't really even change the hash - it really only shifts the hash around in the hash table. To make matters worse, the insane big constant is different on 32-bit and 64-bit builds, even though the name hash bits we use are always 32-bit (and the bits from the pointer we mix in effectively are too). It's all total voodoo programming, in other words. Now, some testing and analysis of the hash chains shows that the rest of the hash function seems to be fairly good. It does pick the right bits of the parent dentry pointer, for example, and while it's generally a bad idea to use an xor to mix down the upper bits (because if there is a repeating pattern, the xor can cause "destructive interference"), it seems to not have been a disaster. For example, replacing the hash with the normal "hash_long()" code (that uses the GOLDEN_RATIO_PRIME constant correctly, btw) actually just makes the hash worse. The hand-picked hash knew which bits of the pointer had the highest entropy, and hash_long() ends up mixing bits less optimally at least in some trivial tests. So the hash function overall seems fine, it just has that really odd "shift result around by a constant xor". So get rid of the silly xor, and replace the down-mixing of the bits with an add instead of an xor that tends to not have the same kind of destructive interference issues. Some stats on the resulting hash chains shows that they look statistically identical before and after, but the code is simpler and no longer makes you go "WTF?". Also, the incoming hash really is just "unsigned int", not a long, and there's no real point to worry about the high 26 bits of the dentry pointer for the 64-bit case, because they are all going to be identical anyway. So also change the hashing to be done in the more natural 'unsigned int' that is the real size of the actual hashed data anyway. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-08vfs: use 'unsigned long' accesses for dcache name comparison and hashingLinus Torvalds
Ok, this is hacky, and only works on little-endian machines with goo unaligned handling. And even then only with CONFIG_DEBUG_PAGEALLOC disabled, since it can access up to 7 bytes after the pathname. But it runs like a bat out of hell. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-04vfs: move dentry_cmp from <linux/dcache.h> to fs/dcache.cLinus Torvalds
It's only used inside fs/dcache.c, and we're going to play games with it for the word-at-a-time patches. This time we really don't even want to export it, because it really is an internal function to fs/dcache.c, and has been since it was introduced. Having it in that extremely hot header file (it's included in pretty much everything, thanks to <linux/fs.h>) is a disaster for testing different versions, and is utterly pointless. We really should have some kind of header file diet thing, where we figure out which parts of header files are really better off private and only result in more expensive compiles. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-02vfs: trivial __d_lookup_rcu() cleanupsLinus Torvalds
These don't change any semantics, but they clean up the code a bit and mark some arguments appropriately 'const'. They came up as I was doing the word-at-a-time dcache name accessor code, and cleaning this up now allows me to send out a smaller relevant interesting patch for the experimental stuff. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-28fs: reduce the use of module.h wherever possiblePaul Gortmaker
For files only using THIS_MODULE and/or EXPORT_SYMBOL, map them onto including export.h -- or if the file isn't even using those, then just delete the include. Fix up any implicit include dependencies that were being masked by module.h along the way. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-02-13vfs: fix panic in __d_lookup() with high dentry hashtable countsDimitri Sivanich
When the number of dentry cache hash table entries gets too high (2147483648 entries), as happens by default on a 16TB system, use of a signed integer in the dcache_init() initialization loop prevents the dentry_hashtable from getting initialized, causing a panic in __d_lookup(). Fix this in dcache_init() and similar areas. Signed-off-by: Dimitri Sivanich <sivanich@sgi.com> Acked-by: David S. Miller <davem@davemloft.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-13Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: ceph: ensure prealloc_blob is in place when removing xattr rbd: initialize snap_rwsem in rbd_add() ceph: enable/disable dentry complete flags via mount option vfs: export symbol d_find_any_alias() ceph: always initialize the dentry in open_root_dentry() libceph: remove useless return value for osd_client __send_request() ceph: avoid iput() while holding spinlock in ceph_dir_fsync ceph: avoid useless dget/dput in encode_fh ceph: dereference pointer after checking for NULL crush: fix force for non-root TAKE ceph: remove unnecessary d_fsdata conditional checks ceph: Use kmemdup rather than duplicating its implementation Fix up conflicts in fs/ceph/super.c (d_alloc_root() failure handling vs always initialize the dentry in open_root_dentry)
2012-01-12vfs: export symbol d_find_any_alias()Sage Weil
Ceph needs this. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sage Weil <sage@newdream.net>
2012-01-10fix shrink_dcache_parent() livelockMiklos Szeredi
Two (or more) concurrent calls of shrink_dcache_parent() on the same dentry may cause shrink_dcache_parent() to loop forever. Here's what appears to happen: 1 - CPU0: select_parent(P) finds C and puts it on dispose list, returns 1 2 - CPU1: select_parent(P) locks P->d_lock 3 - CPU0: shrink_dentry_list() locks C->d_lock dentry_kill(C) tries to lock P->d_lock but fails, unlocks C->d_lock 4 - CPU1: select_parent(P) locks C->d_lock, moves C from dispose list being processed on CPU0 to the new dispose list, returns 1 5 - CPU0: shrink_dentry_list() finds dispose list empty, returns 6 - Goto 2 with CPU0 and CPU1 switched Basically select_parent() steals the dentry from shrink_dentry_list() and thinks it found a new one, causing shrink_dentry_list() to think it's making progress and loop over and over. One way to trigger this is to make udev calls stat() on the sysfs file while it is going away. Having a file in /lib/udev/rules.d/ with only this one rule seems to the trick: ATTR{vendor}=="0x8086", ATTR{device}=="0x10ca", ENV{PCI_SLOT_NAME}="%k", ENV{MATCHADDR}="$attr{address}", RUN+="/bin/true" Then execute the following loop: while true; do echo -bond0 > /sys/class/net/bonding_masters echo +bond0 > /sys/class/net/bonding_masters echo -bond1 > /sys/class/net/bonding_masters echo +bond1 > /sys/class/net/bonding_masters done One fix would be to check all callers and prevent concurrent calls to shrink_dcache_parent(). But I think a better solution is to stop the stealing behavior. This patch adds a new dentry flag that is set when the dentry is added to the dispose list. The flag is cleared in dentry_lru_del() in case the dentry gets a new reference just before being pruned. If the dentry has this flag, select_parent() will skip it and let shrink_dentry_list() retry pruning it. With select_parent() skipping those dentries there will not be the appearance of progress (new dentries found) when there is none, hence shrink_dcache_parent() will not loop forever. Set the flag is also set in prune_dcache_sb() for consistency as suggested by Linus. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> CC: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-09vfs: new helper - d_make_root()Al Viro
d_alloc_root() with iput() in case of allocation failure... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-09dcache: use a dispose list in select_parentDave Chinner
select_parent currently abuses the dentry cache LRU to provide cleanup features for child dentries that need to be freed. It moves them to the tail of the LRU, then tells shrink_dcache_parent() to calls __shrink_dcache_sb to unconditionally move them to a dispose list (as DCACHE_REFERENCED is ignored). __shrink_dcache_sb() has to relock the dentries to move them off the LRU onto the dispose list, but otherwise does not touch the dentries that select_parent() moved to the tail of the LRU. It then passses the dispose list to shrink_dentry_list() which tries to free the dentries. IOWs, the use of __shrink_dcache_sb() is superfluous - we can build exactly the same list of dentries for disposal directly in select_parent() and call shrink_dentry_list() instead of calling __shrink_dcache_sb() to do that. This means that we avoid long holds on the lru lock walking the LRU moving dentries to the dispose list We also avoid the need to relock each dentry just to move it off the LRU, reducing the numebr of times we lock each dentry to dispose of them in shrink_dcache_parent() from 3 to 2 times. Further, we remove one of the two callers of __shrink_dcache_sb(). This also means that __shrink_dcache_sb can be moved into back into prune_dcache_sb() and we no longer have to handle referenced dentries conditionally, simplifying the code. Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: mnt_ns moved to struct mountAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: move mnt_mountpoint to struct mountAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: now it can be done - make mnt_parent point to struct mountAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: mnt_parent moved to struct mountAl Viro
the second victim... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: spread struct mount - mnt_has_parentAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: more mnt_parent cleanupsAl Viro
a) mount --move is checking that ->mnt_parent is non-NULL before looking if that parent happens to be shared; ->mnt_parent is never NULL and it's not even an misspelled !mnt_has_parent() b) pivot_root open-codes is_path_reachable(), poorly. c) so does path_is_under(), while we are at it. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: new internal helper: mnt_has_parent(mnt)Al Viro
vfsmounts have ->mnt_parent pointing either to a different vfsmount or to itself; it's never NULL and termination condition in loops traversing the tree towards root is mnt == mnt->mnt_parent. At least one place (see the next patch) is confused about what's going on; let's add an explicit helper checking it right way and use it in all places where we need it. Not that there had been too many, but... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-12-06fix apparmor dereferencing potentially freed dentry, sanitize __d_path() APIAl Viro
__d_path() API is asking for trouble and in case of apparmor d_namespace_path() getting just that. The root cause is that when __d_path() misses the root it had been told to look for, it stores the location of the most remote ancestor in *root. Without grabbing references. Sure, at the moment of call it had been pinned down by what we have in *path. And if we raced with umount -l, we could have very well stopped at vfsmount/dentry that got freed as soon as prepend_path() dropped vfsmount_lock. It is safe to compare these pointers with pre-existing (and known to be still alive) vfsmount and dentry, as long as all we are asking is "is it the same address?". Dereferencing is not safe and apparmor ended up stepping into that. d_namespace_path() really wants to examine the place where we stopped, even if it's not connected to our namespace. As the result, it looked at ->d_sb->s_magic of a dentry that might've been already freed by that point. All other callers had been careful enough to avoid that, but it's really a bad interface - it invites that kind of trouble. The fix is fairly straightforward, even though it's bigger than I'd like: * prepend_path() root argument becomes const. * __d_path() is never called with NULL/NULL root. It was a kludge to start with. Instead, we have an explicit function - d_absolute_root(). Same as __d_path(), except that it doesn't get root passed and stops where it stops. apparmor and tomoyo are using it. * __d_path() returns NULL on path outside of root. The main caller is show_mountinfo() and that's precisely what we pass root for - to skip those outside chroot jail. Those who don't want that can (and do) use d_path(). * __d_path() root argument becomes const. Everyone agrees, I hope. * apparmor does *NOT* try to use __d_path() or any of its variants when it sees that path->mnt is an internal vfsmount. In that case it's definitely not mounted anywhere and dentry_path() is exactly what we want there. Handling of sysctl()-triggered weirdness is moved to that place. * if apparmor is asked to do pathname relative to chroot jail and __d_path() tells it we it's not in that jail, the sucker just calls d_absolute_path() instead. That's the other remaining caller of __d_path(), BTW. * seq_path_root() does _NOT_ return -ENAMETOOLONG (it's stupid anyway - the normal seq_file logics will take care of growing the buffer and redoing the call of ->show() just fine). However, if it gets path not reachable from root, it returns SEQ_SKIP. The only caller adjusted (i.e. stopped ignoring the return value as it used to do). Reviewed-by: John Johansen <john.johansen@canonical.com> ACKed-by: John Johansen <john.johansen@canonical.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org
2011-11-20VFS: Log the fact that we've given ELOOP rather than creating a loopDavid Howells
To prevent an NFS server from being used to create a directory loop in an NFS superblock on the client, the following patch was committed: commit 1836750115f20b774e55c032a3893e8c5bdf41ed Author: Al Viro <viro@zeniv.linux.org.uk> Date: Tue Jul 12 21:42:24 2011 -0400 Subject: fix loop checks in d_materialise_unique() This causes ELOOP to be reported to anyone trying to access the dentry that would otherwise cause the kernel to complete the loop. However, no indication is given to the caller as to why an operation that ought to work doesn't. The fault is with the kernel, which doesn't want to try and solve the problem as it gets horrendously messy if there's another mountpoint somewhere in the trees being spliced that can't be moved[*]. [*] The real problem is that we don't handle the excision of a subtree that gets moved _out_ of what we can see. This can happen on the server where a directory is merely moved between two other dirs on the same filesystem, but where destination dir is not accessible by the client. So, given the choice to return ELOOP rather than trying to reconfigure the dentry tree, we should give the caller some indication of why they aren't being allowed to make what should be a legitimate request and log a message. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Sachin Prabhu <sprabhu@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-11-07vfs: d_invalidate() should leave mountpoints aloneAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>