- 07 1月, 2011 19 次提交
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由 Nick Piggin 提交于
It is possible to run dput without taking data structure locks up-front. In many cases where we don't kill the dentry anyway, these locks are not required. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Long lived dcache "multi-step" operations which retry on rename seq can be starved with a lot of rename activity. If they fail after the 1st pass, take the rename_lock for writing to avoid further starvation. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
dcache_lock no longer protects anything. remove it. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
The remaining usages for dcache_lock is to allow atomic, multi-step read-side operations over the directory tree by excluding modifications to the tree. Also, to walk in the leaf->root direction in the tree where we don't have a natural d_lock ordering. This could be accomplished by taking every d_lock, but this would mean a huge number of locks and actually gets very tricky. Solve this instead by using the rename seqlock for multi-step read-side operations, retry in case of a rename so we don't walk up the wrong parent. Concurrent dentry insertions are not serialised against. Concurrent deletes are tricky when walking up the directory: our parent might have been deleted when dropping locks so also need to check and retry for that. We can also use the rename lock in cases where livelock is a worry (and it is introduced in subsequent patch). Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Cover d_name with d_lock in more cases, where there may be concurrent modification to it. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Add a new lock, dcache_inode_lock, to protect the inode's i_dentry list from concurrent modification. d_alias is also protected by d_lock. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Protect d_subdirs and d_child with d_lock, except in filesystems that aren't using dcache_lock for these anyway (eg. using i_mutex). Note: if we change the locking rule in future so that ->d_child protection is provided only with ->d_parent->d_lock, it may allow us to reduce some locking. But it would be an exception to an otherwise regular locking scheme, so we'd have to see some good results. Probably not worthwhile. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Protect d_unhashed(dentry) condition with d_lock. This means keeping DCACHE_UNHASHED bit in synch with hash manipulations. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Make d_count non-atomic and protect it with d_lock. This allows us to ensure a 0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when we start protecting many other dentry members with d_lock. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Add a new lock, dcache_lru_lock, to protect the dcache LRU list from concurrent modification. d_lru is also protected by d_lock, which allows LRU lists to be accessed without the lru lock, using RCU in future patches. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Add a new lock, dcache_hash_lock, to protect the dcache hash table from concurrent modification. d_hash is also protected by d_lock. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Remove dcache_lock locking from hostfs filesystem, and move it into dcache helpers. All that is required is a coherent path name. Protection from concurrent modification of the namespace after path name generation is not provided in current code, because dcache_lock is dropped before the path is used. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Change d_hash so it may be called from lock-free RCU lookups. See similar patch for d_compare for details. For in-tree filesystems, this is just a mechanical change. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Change d_compare so it may be called from lock-free RCU lookups. This does put significant restrictions on what may be done from the callback, however there don't seem to have been any problems with in-tree fses. If some strange use case pops up that _really_ cannot cope with the rcu-walk rules, we can just add new rcu-unaware callbacks, which would cause name lookup to drop out of rcu-walk mode. For in-tree filesystems, this is just a mechanical change. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
smpfs and ncpfs want to update a live dentry name in-place. Rather than have them open code the locking, provide a documented dcache API. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
Change d_delete from a dentry deletion notification to a dentry caching advise, more like ->drop_inode. Require it to be constant and idempotent, and not take d_lock. This is how all existing filesystems use the callback anyway. This makes fine grained dentry locking of dput and dentry lru scanning much simpler. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
percpu_counter library generates quite nasty code, so unless you need to dynamically allocate counters or take fast approximate value, a simple per cpu set of counters is much better. The percpu_counter can never be made to work as well, because it has an indirection from pointer to percpu memory, and it can't use direct this_cpu_inc interfaces because it doesn't use static PER_CPU data, so code will always be worse. In the fastpath, it is the difference between this: incl %gs:nr_dentry # nr_dentry and this: movl percpu_counter_batch(%rip), %edx # percpu_counter_batch, movl $1, %esi #, movq $nr_dentry, %rdi #, call __percpu_counter_add # (plus I clobber registers) __percpu_counter_add: pushq %rbp # movq %rsp, %rbp #, subq $32, %rsp #, movq %rbx, -24(%rbp) #, movq %r12, -16(%rbp) #, movq %r13, -8(%rbp) #, movq %rdi, %rbx # fbc, fbc #APP # 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1 movq %gs:kernel_stack,%rax #, pfo_ret__ # 0 "" 2 #NO_APP incl -8124(%rax) # <variable>.preempt_count movq 32(%rdi), %r12 # <variable>.counters, tcp_ptr__ #APP # 78 "lib/percpu_counter.c" 1 add %gs:this_cpu_off, %r12 # this_cpu_off, tcp_ptr__ # 0 "" 2 #NO_APP movslq (%r12),%r13 #* tcp_ptr__, tmp73 movslq %edx,%rax # batch, batch addq %rsi, %r13 # amount, count cmpq %rax, %r13 # batch, count jge .L27 #, negl %edx # tmp76 movslq %edx,%rdx # tmp76, tmp77 cmpq %rdx, %r13 # tmp77, count jg .L28 #, .L27: movq %rbx, %rdi # fbc, call _raw_spin_lock # addq %r13, 8(%rbx) # count, <variable>.count movq %rbx, %rdi # fbc, movl $0, (%r12) #,* tcp_ptr__ call _raw_spin_unlock # .L29: #APP # 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1 movq %gs:kernel_stack,%rax #, pfo_ret__ # 0 "" 2 #NO_APP decl -8124(%rax) # <variable>.preempt_count movq -8136(%rax), %rax #, D.14625 testb $8, %al #, D.14625 jne .L32 #, .L31: movq -24(%rbp), %rbx #, movq -16(%rbp), %r12 #, movq -8(%rbp), %r13 #, leave ret .p2align 4,,10 .p2align 3 .L28: movl %r13d, (%r12) # count,* jmp .L29 # .L32: call preempt_schedule # .p2align 4,,6 jmp .L31 # .size __percpu_counter_add, .-__percpu_counter_add .p2align 4,,15 Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
The nr_unused counters count the number of objects on an LRU, and as such they are synchronized with LRU object insertion and removal and scanning, and protected under the LRU lock. Making it per-cpu does not actually get any concurrency improvements because of this lock, and summing the counter is much slower, and incrementing/decrementing it costs more code size and is slower too. These counters should stay per-LRU, which currently means global. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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由 Nick Piggin 提交于
d_validate has been broken for a long time. kmem_ptr_validate does not guarantee that a pointer can be dereferenced if it can go away at any time. Even rcu_read_lock doesn't help, because the pointer might be queued in RCU callbacks but not executed yet. So the parent cannot be checked, nor the name hashed. The dentry pointer can not be touched until it can be verified under lock. Hashing simply cannot be used. Instead, verify the parent/child relationship by traversing parent's d_child list. It's slow, but only ncpfs and the destaged smbfs care about it, at this point. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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- 05 1月, 2011 1 次提交
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由 Nick Piggin 提交于
This reverts commit 3825bdb7. You cannot dget() a dentry without having a reference, or holding a lock that guarantees it remains valid. Signed-off-by: NNick Piggin <npiggin@kernel.dk>
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- 26 10月, 2010 7 次提交
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由 Christoph Hellwig 提交于
d_validate does a purely read lookup in the dentry hash, so use RCU read side locking instead of dcache_lock. Split out from a larget patch by Nick Piggin <npiggin@suse.de>. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Christoph Hellwig 提交于
Always do a list_del_init on the LRU to make sure the list_empty invariant for not beeing on the LRU always holds true, and fold dentry_lru_del_init into dentry_lru_del. Replace the dentry_lru_add_tail primitive with a dentry_lru_move_tail operations that simpler when the dentry already is one the list, which is always is. Move the list_empty into dentry_lru_add to fit the scheme of the other lru helpers, and simplify locking once we move to a separate LRU lock. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Christoph Hellwig 提交于
Currently __shrink_dcache_sb has an extremly awkward calling convention because it tries to please very different callers. Split out the main loop into a shrink_dentry_list helper, which gets called directly from shrink_dcache_sb for the cases where all dentries need to be pruned, or from __shrink_dcache_sb for pruning only a certain number of dentries. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Nick Piggin 提交于
dentry referenced bit is only set when installing the dentry back onto the LRU. However with lazy LRU, the dentry can already be on the LRU list at dput time, thus missing out on setting the referenced bit. Fix this. Signed-off-by: NNick Piggin <npiggin@suse.de> Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Christoph Hellwig 提交于
The nr_dentry stat is a globally touched cacheline and atomic operation twice over the lifetime of a dentry. It is used for the benfit of userspace only. Turn it into a per-cpu counter and always decrement it in d_free instead of doing various batching operations to reduce lock hold times in the callers. Based on an earlier patch from Nick Piggin <npiggin@suse.de>. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Christoph Hellwig 提交于
Remove d_callback and always call __d_free with a RCU head. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Christoph Hellwig 提交于
All callers take dcache_lock just around the call to __d_path, so take the lock into it in preparation of getting rid of dcache_lock. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 18 8月, 2010 2 次提交
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由 Nick Piggin 提交于
fs: brlock vfsmount_lock Use a brlock for the vfsmount lock. It must be taken for write whenever modifying the mount hash or associated fields, and may be taken for read when performing mount hash lookups. A new lock is added for the mnt-id allocator, so it doesn't need to take the heavy vfsmount write-lock. The number of atomics should remain the same for fastpath rlock cases, though code would be slightly slower due to per-cpu access. Scalability is not not be much improved in common cases yet, due to other locks (ie. dcache_lock) getting in the way. However path lookups crossing mountpoints should be one case where scalability is improved (currently requiring the global lock). The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node Altix system (high latency to remote nodes), a simple umount microbenchmark (mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it took 6.8s, afterwards took 7.1s, about 5% slower. Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: NNick Piggin <npiggin@kernel.dk> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Nick Piggin 提交于
fs: remove extra lookup in __lookup_hash Optimize lookup for create operations, where no dentry should often be common-case. In cases where it is not, such as unlink, the added overhead is much smaller than the removed. Also, move comments about __d_lookup racyness to the __d_lookup call site. d_lookup is intuitive; __d_lookup is what needs commenting. So in that same vein, add kerneldoc comments to __d_lookup and clean up some of the comments: - We are interested in how the RCU lookup works here, particularly with renames. Make that explicit, and point to the document where it is explained in more detail. - RCU is pretty standard now, and macros make implementations pretty mindless. If we want to know about RCU barrier details, we look in RCU code. - Delete some boring legacy comments because we don't care much about how the code used to work, more about the interesting parts of how it works now. So comments about lazy LRU may be interesting, but would better be done in the LRU or refcount management code. Signed-off-by: NNick Piggin <npiggin@kernel.dk> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 15 8月, 2010 1 次提交
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由 Randy Dunlap 提交于
Fix parameter name in kernel-doc notation (causes a warning). Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 8月, 2010 5 次提交
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由 Miklos Szeredi 提交于
Prepend "(unreachable)" to path strings if the path is not reachable from the current root. Two places updated are - the return string from getcwd() - and symlinks under /proc/$PID. Other uses of d_path() are left unchanged (we know that some old software crashes if /proc/mounts is changed). Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Miklos Szeredi 提交于
__d_path() has 4 callers: d_path() sys_getcwd() seq_path_root() tomoyo_realpath_from_path2() Of these the only one which needs the " (deleted)" ending is d_path(). sys_getcwd() checks for existence before calling __d_path(). seq_path_root() is used to show the mountpoint path in /proc/PID/mountinfo, which is always a positive. And tomoyo doesn't want the deleted ending. Create a helper "path_with_deleted()" as subsequent patches will need this in multiple places. Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Miklos Szeredi 提交于
Split off prepend_path() from __d_path(). This new helper takes an end-of-buffer pointer and buffer-length pointer just like the other prepend_* functions. Move the " (deleted)" postfix out to __d_path(). This patch doesn't change any functionality but paves the way for the following patches. Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Miklos Szeredi 提交于
In the old times pseudo-filesystems set the name of theroot dentry to some prefix like "pipe:" and the name of the child dentry to "[123]" and relied on a hack in __d_path() to replace the preceding slash with the root's name to get "pipe:[123]". Then the d_dname() dentry operation was introduced which solved the same problem without having to pre-fill the name in each dentry. Currently the following pseudo filesystems exist in the kernel: perfmon mtd anon_inode bdev pipe socket Of these only perfmon, anon_inode, pipe and socket create sub-dentries, all of which have now been switched to using d_dname(). bdev and mtd only create inodes. This means that now the hack to overwrite the slash can be removed, so for unreachable paths (e.g. within a detached mount) the path string won't be polluted with garbage. For these cases a subsequent patch will add a prefix, indicating that the path is unreachable. Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Miklos Szeredi 提交于
Add three helpers that retrieve a refcounted copy of the root and cwd from the supplied fs_struct. get_fs_root() get_fs_pwd() get_fs_root_and_pwd() Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 10 8月, 2010 2 次提交
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由 Al Viro 提交于
just delay __put_super() a bit Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
builds path relative to fs root, called under dcache_lock, doesn't append any nonsense to unlinked ones. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 19 7月, 2010 1 次提交
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由 Dave Chinner 提交于
The current shrinker implementation requires the registered callback to have global state to work from. This makes it difficult to shrink caches that are not global (e.g. per-filesystem caches). Pass the shrinker structure to the callback so that users can embed the shrinker structure in the context the shrinker needs to operate on and get back to it in the callback via container_of(). Signed-off-by: NDave Chinner <dchinner@redhat.com> Reviewed-by: NChristoph Hellwig <hch@lst.de>
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- 30 6月, 2010 1 次提交
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由 npiggin@suse.de 提交于
list_for_each_entry_safe is not suitable to protect against concurrent modification of the list. 6754af64 introduced a race in sb walking. list_for_each_entry can use the trick of pinning the current entry in the list before we drop and retake the lock because it subsequently follows cur->next. However list_for_each_entry_safe saves n=cur->next for following before entering the loop body, so when the lock is dropped, n may be deleted. Signed-off-by: NNick Piggin <npiggin@suse.de> Cc: Christoph Hellwig <hch@infradead.org> Cc: John Stultz <johnstul@us.ibm.com> Cc: Frank Mayhar <fmayhar@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 22 5月, 2010 1 次提交
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由 Al Viro 提交于
... and get rid of the last __put_super_and_need_restart() caller Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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