- 24 5月, 2012 1 次提交
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由 Tim Bird 提交于
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: NMark Asselstine <mark.asselstine@windriver.com> Reported-by: NTim Bird <tim.bird@am.sony.com> Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 22 5月, 2012 2 次提交
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由 Linus Torvalds 提交于
This reverts commit 8c01a529. 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: NDave Jones <davej@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Linus Torvalds 提交于
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: NMiklos Szeredi <mszeredi@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Nick Piggin <npiggin@gmail.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 5月, 2012 4 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Linus Torvalds 提交于
Commit 12f8ad4b ("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: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 05 5月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 04 5月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NJana Saout <jana@saout.de> Cc: Peter Anvin <hpa@zytor.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 29 3月, 2012 1 次提交
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由 Michel Lespinasse 提交于
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 18367501 ("fix loop checks in d_materialise_unique()"). Signed-off-by: NMichel 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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 23 3月, 2012 1 次提交
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由 Randy Dunlap 提交于
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: NRandy Dunlap <rdunlap@xenotime.net> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 21 3月, 2012 1 次提交
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由 Al Viro 提交于
all callers converted to d_make_root() by now Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 20 3月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 09 3月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 05 3月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 03 3月, 2012 1 次提交
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由 Linus Torvalds 提交于
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: NLinus Torvalds <torvalds@linux-foundation.org>
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- 29 2月, 2012 1 次提交
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由 Paul Gortmaker 提交于
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: NPaul Gortmaker <paul.gortmaker@windriver.com>
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- 14 2月, 2012 1 次提交
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由 Dimitri Sivanich 提交于
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: NDimitri Sivanich <sivanich@sgi.com> Acked-by: NDavid S. Miller <davem@davemloft.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 13 1月, 2012 1 次提交
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由 Sage Weil 提交于
Ceph needs this. Reviewed-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NSage Weil <sage@newdream.net>
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- 11 1月, 2012 1 次提交
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由 Miklos Szeredi 提交于
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: NMiklos Szeredi <mszeredi@suse.cz> CC: stable@vger.kernel.org Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 10 1月, 2012 2 次提交
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由 Al Viro 提交于
d_alloc_root() with iput() in case of allocation failure... Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Dave Chinner 提交于
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: NDave Chinner <dchinner@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 04 1月, 2012 7 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
the second victim... Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
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: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
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: NAl Viro <viro@zeniv.linux.org.uk>
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- 07 12月, 2011 1 次提交
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由 Al Viro 提交于
__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: NJohn Johansen <john.johansen@canonical.com> ACKed-by: NJohn Johansen <john.johansen@canonical.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org
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- 21 11月, 2011 1 次提交
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由 David Howells 提交于
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 18367501 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: NDavid Howells <dhowells@redhat.com> Acked-by: NSachin Prabhu <sprabhu@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 08 11月, 2011 1 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 02 11月, 2011 1 次提交
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由 Sage Weil 提交于
This adds a d_prune dentry operation that is called by the VFS prior to pruning (i.e. unhashing and killing) a hashed dentry from the dcache. Wrap dentry_lru_del() and use the new _prune() helper in the cases where we are about to unhash and kill the dentry. This will be used by Ceph to maintain a flag indicating whether the complete contents of a directory are contained in the dcache, allowing it to satisfy lookups and readdir without addition server communication. Renumber a few DCACHE_* #defines to group DCACHE_OP_PRUNE with the other DCACHE_OP_ bits. Signed-off-by: NSage Weil <sage@newdream.net> Signed-off-by: NChristoph Hellwig <hch@lst.de>
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- 07 8月, 2011 1 次提交
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由 Linus Torvalds 提交于
Gcc tends to generate better code with small integers, including the DCACHE_xyz flag tests - so move the common ones to be first in the list. Also just remove the unused DCACHE_INOTIFY_PARENT_WATCHED and DCACHE_AUTOFS_PENDING values, their users no longer exists in the source tree. And add a "unlikely()" to the DCACHE_OP_COMPARE test, since we want the common case to be a nice straight-line fall-through. Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 04 8月, 2011 1 次提交
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由 Randy Dunlap 提交于
Fix new kernel-doc warning in fs/dcache.c: Warning(fs/dcache.c:797): No description found for parameter 'sb' Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 01 8月, 2011 3 次提交
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由 David Howells 提交于
Reorganise shrink_dcache_for_umount_subtree() in light of the demise of dcache_lock. Without that dcache_lock, there is no need for the batching of removal of dentries from the system under it (we wanted to make intensive use of the locked data whilst we held it, but didn't want to hold it for long at a time). This works, provided the preceding patch is correct in its removal of locking on dentry->d_lock on the basis that no one should be locking these dentries any more as the whole superblock is defunct. With this patch, the calls to dentry_lru_del() and __d_shrink() are placed at the point where each dentry is detached handled. It is possible that, as an alternative, the batching should still be done - but only for dentry_lru_del() of all a dentry's children in one go. In such a case, the batching would be done under dcache_lru_lock. Signed-off-by: NDavid Howells <dhowells@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 David Howells 提交于
Locks of the dcache_lock were replaced by locks of dentry->d_lock in commits such as: 23044507 2fd6b7f5 as part of the RCU-based pathwalk changes, despite the fact that the caller (shrink_dcache_for_umount()) notes in the banner comment the reasons that d_lock is not necessary in these functions: /* * destroy the dentries attached to a superblock on unmounting * - we don't need to use dentry->d_lock because: * - the superblock is detached from all mountings and open files, so the * dentry trees will not be rearranged by the VFS * - s_umount is write-locked, so the memory pressure shrinker will ignore * any dentries belonging to this superblock that it comes across * - the filesystem itself is no longer permitted to rearrange the dentries * in this superblock */ So remove these locks. If the locks are actually necessary, then this banner comment should be altered instead. The hash table chains are protected by 1-bit locks in the hash table heads, so those shouldn't be a problem. Note that to make this work, __d_drop() has to be split so that the RCUwalk barrier can be avoided. This causes problems otherwise as it has an assertion that dentry->d_lock is locked - but there is no need for that as no one else can be trying to access this dentry, except to step over it (and that should be handled by d_free(), I think). Signed-off-by: NDavid Howells <dhowells@redhat.com> Cc: Nick Piggin <npiggin@kernel.dk> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 David Howells 提交于
Remove the detached-dentry counter from shrink_dcache_for_umount_subtree() as the value it computes is no longer used as of commit 312d3ca8 which made the nr_dentry counters summed per-CPU rather than global atomic. Signed-off-by: NDavid Howells <dhowells@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 27 7月, 2011 1 次提交
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由 Jeff Layton 提交于
Adding a comment to d_materialise_unique per Al's request... d_move and __d_move have some pretty substantial locking requirements, but they are not clearly documented. Add some comments spelling them out. Also, document the requirement for the i_mutex of the parent in d_materialise_unique. Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: NJeff Layton <jlayton@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 22 7月, 2011 1 次提交
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由 Linus Torvalds 提交于
It seems to hurt performance in real life. Yes, the inode will be used later, but the conditional doesn't seem to predict all that well (negative dentries are not uncommon) and it looks like the cost of prefetching is simply higher than depending on the cache doing the right thing. As usual. Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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