- 29 5月, 2016 4 次提交
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由 George Spelvin 提交于
The original name was simply hash_string(), but that conflicted with a function with that name in drivers/base/power/trace.c, and I decided that calling it "hashlen_" was better anyway. But you have to do it in two places. [ This caused build errors for architectures that don't define CONFIG_DCACHE_WORD_ACCESS - Linus ] Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net> Reported-by: NGuenter Roeck <linux@roeck-us.net> Fixes: fcfd2fbf ("fs/namei.c: Add hashlen_string() function") Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 George Spelvin 提交于
This is just the infrastructure; there are no users yet. This is modelled on CONFIG_ARCH_RANDOM; a CONFIG_ symbol declares the existence of <asm/hash.h>. That file may define its own versions of various functions, and define HAVE_* symbols (no CONFIG_ prefix!) to suppress the generic ones. Included is a self-test (in lib/test_hash.c) that verifies the basics. It is NOT in general required that the arch-specific functions compute the same thing as the generic, but if a HAVE_* symbol is defined with the value 1, then equality is tested. Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Greg Ungerer <gerg@linux-m68k.org> Cc: Andreas Schwab <schwab@linux-m68k.org> Cc: Philippe De Muyter <phdm@macq.eu> Cc: linux-m68k@lists.linux-m68k.org Cc: Alistair Francis <alistai@xilinx.com> Cc: Michal Simek <michal.simek@xilinx.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: uclinux-h8-devel@lists.sourceforge.jp
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由 George Spelvin 提交于
Patch 0fed3ac8 improved the hash mixing, but the function is slower than necessary; there's a 7-instruction dependency chain (10 on x86) each loop iteration. Word-at-a-time access is a very tight loop (which is good, because link_path_walk() is one of the hottest code paths in the entire kernel), and the hash mixing function must not have a longer latency to avoid slowing it down. There do not appear to be any published fast hash functions that: 1) Operate on the input a word at a time, and 2) Don't need to know the length of the input beforehand, and 3) Have a single iterated mixing function, not needing conditional branches or unrolling to distinguish different loop iterations. One of the algorithms which comes closest is Yann Collet's xxHash, but that's two dependent multiplies per word, which is too much. The key insights in this design are: 1) Barring expensive ops like multiplies, to diffuse one input bit across 64 bits of hash state takes at least log2(64) = 6 sequentially dependent instructions. That is more cycles than we'd like. 2) An operation like "hash ^= hash << 13" requires a second temporary register anyway, and on a 2-operand machine like x86, it's three instructions. 3) A better use of a second register is to hold a two-word hash state. With careful design, no temporaries are needed at all, so it doesn't increase register pressure. And this gets rid of register copying on 2-operand machines, so the code is smaller and faster. 4) Using two words of state weakens the requirement for one-round mixing; we now have two rounds of mixing before cancellation is possible. 5) A two-word hash state also allows operations on both halves to be done in parallel, so on a superscalar processor we get more mixing in fewer cycles. I ended up using a mixing function inspired by the ChaCha and Speck round functions. It is 6 simple instructions and 3 cycles per iteration (assuming multiply by 9 can be done by an "lea" instruction): x ^= *input++; y ^= x; x = ROL(x, K1); x += y; y = ROL(y, K2); y *= 9; Not only is this reversible, two consecutive rounds are reversible: if you are given the initial and final states, but not the intermediate state, it is possible to compute both input words. This means that at least 3 words of input are required to create a collision. (It also has the property, used by hash_name() to avoid a branch, that it hashes all-zero to all-zero.) The rotate constants K1 and K2 were found by experiment. The search took a sample of random initial states (I used 1023) and considered the effect of flipping each of the 64 input bits on each of the 128 output bits two rounds later. Each of the 8192 pairs can be considered a biased coin, and adding up the Shannon entropy of all of them produces a score. The best-scoring shifts also did well in other tests (flipping bits in y, trying 3 or 4 rounds of mixing, flipping all 64*63/2 pairs of input bits), so the choice was made with the additional constraint that the sum of the shifts is odd and not too close to the word size. The final state is then folded into a 32-bit hash value by a less carefully optimized multiply-based scheme. This also has to be fast, as pathname components tend to be short (the most common case is one iteration!), but there's some room for latency, as there is a fair bit of intervening logic before the hash value is used for anything. (Performance verified with "bonnie++ -s 0 -n 1536:-2" on tmpfs. I need a better benchmark; the numbers seem to show a slight dip in performance between 4.6.0 and this patch, but they're too noisy to quote.) Special thanks to Bruce fields for diligent testing which uncovered a nasty fencepost error in an earlier version of this patch. [checkpatch.pl formatting complaints noted and respectfully disagreed with.] Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net> Tested-by: NJ. Bruce Fields <bfields@redhat.com>
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由 George Spelvin 提交于
We'd like to make more use of the highly-optimized dcache hash functions throughout the kernel, rather than have every subsystem create its own, and a function that hashes basic null-terminated strings is required for that. (The name is to emphasize that it returns both hash and length.) It's actually useful in the dcache itself, specifically d_alloc_name(). Other uses in the next patch. full_name_hash() is also tweaked to make it more generally useful: 1) Take a "char *" rather than "unsigned char *" argument, to be consistent with hash_name(). 2) Handle zero-length inputs. If we want more callers, we don't want to make them worry about corner cases. Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
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- 17 5月, 2016 1 次提交
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由 George Spelvin 提交于
The hash mixing between adding the next 64 bits of name was just a bit weak. Replaced with a still very fast but slightly more effective mixing function. Signed-off-by: NGeorge Spelvin <linux@horizon.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 5月, 2016 2 次提交
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由 Miklos Szeredi 提交于
Overlayfs needs lookup without inode_permission() and already has the name hash (in form of dentry->d_name on overlayfs dentry). It also doesn't support filesystems with d_op->d_hash() so basically it only needs the actual hashed lookup from lookup_one_len_unlocked() So add a new helper that does unlocked lookup of a hashed name. Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
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由 Miklos Szeredi 提交于
If a file is renamed to a hardlink of itself POSIX specifies that rename(2) should do nothing and return success. This condition is checked in vfs_rename(). However it won't detect hard links on overlayfs where these are given separate inodes on the overlayfs layer. Overlayfs itself detects this condition and returns success without doing anything, but then vfs_rename() will proceed as if this was a successful rename (detach_mounts(), d_move()). The correct thing to do is to detect this condition before even calling into overlayfs. This patch does this by calling vfs_select_inode() to get the underlying inodes. Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com> Cc: <stable@vger.kernel.org> # v4.2+
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- 03 5月, 2016 19 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
... and lose the duplicate IS_DEADDIR() - we'd already checked that. 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
It should never return positives; however, with Linux S&M crowd involved, no bogosity is impossible. Results would be unpleasant... Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
nobody else needs that transformation. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
make it conditional on *opened & FILE_OPENED; in addition to getting rid of exit_fput: thing, it simplifies atomic_open() cleanup on may_open() failure. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
may_open() will catch it 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
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
Lift IS_DEADDIR handling up into the part common with atomic_open(), remove it from the latter. Collapse permission checks into the call of may_o_create(), getting it closer to atomic_open() case. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
do_last() and lookup_open() simpler that way and so does O_PATH itself. As it bloody well should: we find what the pathname resolves to, same way as in stat() et.al. and associate it with FMODE_PATH struct file. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
ta-da! The main issue is the lack of down_write_killable(), so the places like readdir.c switched to plain inode_lock(); once killable variants of rwsem primitives appear, that'll be dealt with. lockdep side also might need more work Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
If we *do* run into an in-lookup match, we need to wait for it to cease being in-lookup. Fortunately, we do have unused space in in-lookup dentries - d_lru is never looked at until it stops being in-lookup. So we can stash a pointer to wait_queue_head from stack frame of the caller of ->lookup(). Some precautions are needed while waiting, but it's not that hard - we do hold a reference to dentry we are waiting for, so it can't go away. If it's found to be in-lookup the wait_queue_head is still alive and will remain so at least while ->d_lock is held. Moreover, the condition we are waiting for becomes true at the same point where everything on that wq gets woken up, so we can just add ourselves to the queue once. d_alloc_parallel() gets a pointer to wait_queue_head_t from its caller; lookup_slow() adjusted, d_add_ci() taught to use d_alloc_parallel() if the dentry passed to it happens to be in-lookup one (i.e. if it's been called from the parallel lookup). That's pretty much it - all that remains is to switch ->i_mutex to rwsem and have lookup_slow() take it shared. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
We will need to be able to check if there is an in-lookup dentry with matching parent/name. Right now it's impossible, but as soon as start locking directories shared such beasts will appear. Add a secondary hash for locating those. Hash chains go through the same space where d_alias will be once it's not in-lookup anymore. Search is done under the same bitlock we use for modifications - with the primary hash we can rely on d_rehash() into the wrong chain being the worst that could happen, but here the pointers are buggered once it's removed from the chain. On the other hand, the chains are not going to be long and normally we'll end up adding to the chain anyway. That allows us to avoid bothering with ->d_lock when doing the comparisons - everything is stable until removed from chain. New helper: d_alloc_parallel(). Right now it allocates, verifies that no hashed and in-lookup matches exist and adds to in-lookup hash. Returns ERR_PTR() for error, hashed match (in the unlikely case it's been found) or new dentry. In-lookup matches trigger BUG() for now; that will change in the next commit when we introduce waiting for ongoing lookup to finish. Note that in-lookup matches won't be possible until we actually go for shared locking. lookup_slow() switched to use of d_alloc_parallel(). Again, these commits are separated only for making it easier to review. All this machinery will start doing something useful only when we go for shared locking; it's just that the combination is too large for my taste. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
marked as such when (would be) parallel lookup is about to pass them to actual ->lookup(); unmarked when * __d_add() is about to make it hashed, positive or not. * __d_move() (from d_splice_alias(), directly or via __d_unalias()) puts a preexisting dentry in its place * in caller of ->lookup() if it has escaped all of the above. Bug (WARN_ON, actually) if it reaches the final dput() or d_instantiate() while still marked such. As the result, we are guaranteed that for as long as the flag is set, dentry will * remain negative unhashed with positive refcount * never have its ->d_alias looked at * never have its ->d_lru looked at * never have its ->d_parent and ->d_name changed Right now we have at most one such for any given parent directory. With parallel lookups that restriction will weaken to * only exist when parent is locked shared * at most one with given (parent,name) pair (comparison of names is according to ->d_compare()) * only exist when there's no hashed dentry with the same (parent,name) Transition will take the next several commits; unfortunately, we'll only be able to switch to rwsem at the end of this series. The reason for not making it a single patch is to simplify review. New primitives: d_in_lookup() (a predicate checking if dentry is in the in-lookup state) and d_lookup_done() (tells the system that we are done with lookup and if it's still marked as in-lookup, it should cease to be such). 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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- 01 5月, 2016 2 次提交
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由 Mimi Zohar 提交于
Commit 3034a146 "ima: pass 'opened' flag to identify newly created files" stopped identifying empty files as new files. However new empty files can be created using the mknodat syscall. On systems with IMA-appraisal enabled, these empty files are not labeled with security.ima extended attributes properly, preventing them from subsequently being opened in order to write the file data contents. This patch defines a new hook named ima_post_path_mknod() to mark these empty files, created using mknodat, as new in order to allow the file data contents to be written. In addition, files with security.ima xattrs containing a file signature are considered "immutable" and can not be modified. The file contents need to be written, before signing the file. This patch relaxes this requirement for new files, allowing the file signature to be written before the file contents. Changelog: - defer identifying files with signatures stored as security.ima (based on Dmitry Rozhkov's comments) - removing tests (eg. dentry, dentry->d_inode, inode->i_size == 0) (based on Al's review) Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com> Cc: Al Viro <<viro@zeniv.linux.org.uk> Tested-by: NDmitry Rozhkov <dmitry.rozhkov@linux.intel.com>
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由 Al Viro 提交于
* if we have a hashed negative dentry and either CREAT|EXCL on r/o filesystem, or CREAT|TRUNC on r/o filesystem, or CREAT|EXCL with failing may_o_create(), we should fail with EROFS or the error may_o_create() has returned, but not ENOENT. Which is what the current code ends up returning. * if we have CREAT|TRUNC hitting a regular file on a read-only filesystem, we can't fail with EROFS here. At the very least, not until we'd done follow_managed() - we might have a writable file (or a device, for that matter) bound on top of that one. Moreover, the code downstream will see that O_TRUNC and attempt to grab the write access (*after* following possible mount), so if we really should fail with EROFS, it will happen. No need to do that inside atomic_open(). The real logics is much simpler than what the current code is trying to do - if we decided to go for simple lookup, ended up with a negative dentry *and* had create_error set, fail with create_error. No matter whether we'd got that negative dentry from lookup_real() or had found it in dcache. Cc: stable@vger.kernel.org # v3.6+ Acked-by: NMiklos Szeredi <mszeredi@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 11 4月, 2016 1 次提交
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由 Al Viro 提交于
... and neither can ever be NULL Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 06 4月, 2016 1 次提交
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由 Christoph Hellwig 提交于
Also drop the now unused readlink_copy export. [dchinner: use d_inode(dentry) rather than dentry->d_inode] Signed-off-by: NChristoph Hellwig <hch@lst.de> Reviewed-by: NDave Chinner <dchinner@redhat.com> Signed-off-by: NDave Chinner <david@fromorbit.com>
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- 31 3月, 2016 2 次提交
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由 Andreas Gruenbacher 提交于
When get_acl() is called for an inode whose ACL is not cached yet, the get_acl inode operation is called to fetch the ACL from the filesystem. The inode operation is responsible for updating the cached acl with set_cached_acl(). This is done without locking at the VFS level, so another task can call set_cached_acl() or forget_cached_acl() before the get_acl inode operation gets to calling set_cached_acl(), and then get_acl's call to set_cached_acl() results in caching an outdate ACL. Prevent this from happening by setting the cached ACL pointer to a task-specific sentinel value before calling the get_acl inode operation. Move the responsibility for updating the cached ACL from the get_acl inode operations to get_acl(). There, only set the cached ACL if the sentinel value hasn't changed. The sentinel values are chosen to have odd values. Likewise, the value of ACL_NOT_CACHED is odd. In contrast, ACL object pointers always have an even value (ACLs are aligned in memory). This allows to distinguish uncached ACLs values from ACL objects. In addition, switch from guarding inode->i_acl and inode->i_default_acl upates by the inode->i_lock spinlock to using xchg() and cmpxchg(). Filesystems that do not want ACLs returned from their get_acl inode operations to be cached must call forget_cached_acl() to prevent the VFS from doing so. (Patch written by Al Viro and Andreas Gruenbacher.) Signed-off-by: NAndreas Gruenbacher <agruenba@redhat.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
We should try to trigger automount *before* bailing out on negative dentry. Reported-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com> Reported-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com> Reported-by: NArend van Spriel <arend@broadcom.com> Tested-by: NArend van Spriel <arend@broadcom.com> Tested-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 28 3月, 2016 1 次提交
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由 Al Viro 提交于
... as well as unix_mknod() and may_o_create() Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 14 3月, 2016 7 次提交
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由 Al Viro 提交于
the last user is gone Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
... and make mountpoint_last() use it. That makes all candidates for lookup with parent locked shared go through lookup_slow(). Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
Return dentry and don't pass nameidata or path; lift crossing mountpoints into the caller. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
No need to lock parent just because of ->d_revalidate() on child; contrary to the stale comment, lookup_dcache() *can* be used without locking the parent. Result can be moved as soon as we return, of course, but the same is true for lookup_one_len_unlocked() itself. 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
Have lookup_fast() return 1 on success and 0 on "need to fall back"; lookup_slow() and follow_managed() return positive (1) on success. 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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