From: Jan Kara <jack@suse.cz> To: linux-fsdevel@vger.kernel.org Cc: Jan Kara <jack@suse.cz>, linux-nvdimm@lists.01.org, NeilBrown <neilb@suse.com>, "Wilcox, Matthew R" <matthew.r.wilcox@intel.com> Subject: [PATCH 02/10] radix-tree: make 'indirect' bit available to exception entries. Date: Mon, 21 Mar 2016 14:22:47 +0100 [thread overview] Message-ID: <1458566575-28063-3-git-send-email-jack@suse.cz> (raw) In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz> From: NeilBrown <neilb@suse.com> A pointer to a radix_tree_node will always have the 'exception' bit cleared, so if the exception bit is set the value cannot be an indirect pointer. Thus it is safe to make the 'indirect bit' available to store extra information in exception entries. This patch adds a 'PTR_MASK' and a value is only treated as an indirect (pointer) entry the 2 ls-bits are '01'. The change in radix-tree.c ensures the stored value still looks like an indirect pointer, and saves a load as well. We could swap the two bits and so keep all the exectional bits contigious. But I have other plans for that bit.... Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Jan Kara <jack@suse.cz> --- include/linux/radix-tree.h | 11 +++++++++-- lib/radix-tree.c | 2 +- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index d08d6ec3bf53..2bc8c5829441 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -41,8 +41,13 @@ * Indirect pointer in fact is also used to tag the last pointer of a node * when it is shrunk, before we rcu free the node. See shrink code for * details. + * + * To allow an exception entry to only lose one bit, we ignore + * the INDIRECT bit when the exception bit is set. So an entry is + * indirect if the least significant 2 bits are 01. */ #define RADIX_TREE_INDIRECT_PTR 1 +#define RADIX_TREE_INDIRECT_MASK 3 /* * A common use of the radix tree is to store pointers to struct pages; * but shmem/tmpfs needs also to store swap entries in the same tree: @@ -54,7 +59,8 @@ static inline int radix_tree_is_indirect_ptr(void *ptr) { - return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); + return ((unsigned long)ptr & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR; } /*** radix-tree API starts here ***/ @@ -222,7 +228,8 @@ static inline void *radix_tree_deref_slot_protected(void **pslot, */ static inline int radix_tree_deref_retry(void *arg) { - return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); + return unlikely(((unsigned long)arg & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR); } /** diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 1624c4117961..c6af1a445b67 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1412,7 +1412,7 @@ static inline void radix_tree_shrink(struct radix_tree_root *root) * to force callers to retry. */ if (root->height == 0) - *((unsigned long *)&to_free->slots[0]) |= + *((unsigned long *)&to_free->slots[0]) = RADIX_TREE_INDIRECT_PTR; radix_tree_node_free(to_free); -- 2.6.2 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz> To: linux-fsdevel@vger.kernel.org Cc: "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>, Ross Zwisler <ross.zwisler@linux.intel.com>, Dan Williams <dan.j.williams@intel.com>, linux-nvdimm@lists.01.org, NeilBrown <neilb@suse.com>, Jan Kara <jack@suse.cz> Subject: [PATCH 02/10] radix-tree: make 'indirect' bit available to exception entries. Date: Mon, 21 Mar 2016 14:22:47 +0100 [thread overview] Message-ID: <1458566575-28063-3-git-send-email-jack@suse.cz> (raw) In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz> From: NeilBrown <neilb@suse.com> A pointer to a radix_tree_node will always have the 'exception' bit cleared, so if the exception bit is set the value cannot be an indirect pointer. Thus it is safe to make the 'indirect bit' available to store extra information in exception entries. This patch adds a 'PTR_MASK' and a value is only treated as an indirect (pointer) entry the 2 ls-bits are '01'. The change in radix-tree.c ensures the stored value still looks like an indirect pointer, and saves a load as well. We could swap the two bits and so keep all the exectional bits contigious. But I have other plans for that bit.... Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Jan Kara <jack@suse.cz> --- include/linux/radix-tree.h | 11 +++++++++-- lib/radix-tree.c | 2 +- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index d08d6ec3bf53..2bc8c5829441 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -41,8 +41,13 @@ * Indirect pointer in fact is also used to tag the last pointer of a node * when it is shrunk, before we rcu free the node. See shrink code for * details. + * + * To allow an exception entry to only lose one bit, we ignore + * the INDIRECT bit when the exception bit is set. So an entry is + * indirect if the least significant 2 bits are 01. */ #define RADIX_TREE_INDIRECT_PTR 1 +#define RADIX_TREE_INDIRECT_MASK 3 /* * A common use of the radix tree is to store pointers to struct pages; * but shmem/tmpfs needs also to store swap entries in the same tree: @@ -54,7 +59,8 @@ static inline int radix_tree_is_indirect_ptr(void *ptr) { - return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); + return ((unsigned long)ptr & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR; } /*** radix-tree API starts here ***/ @@ -222,7 +228,8 @@ static inline void *radix_tree_deref_slot_protected(void **pslot, */ static inline int radix_tree_deref_retry(void *arg) { - return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); + return unlikely(((unsigned long)arg & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR); } /** diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 1624c4117961..c6af1a445b67 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1412,7 +1412,7 @@ static inline void radix_tree_shrink(struct radix_tree_root *root) * to force callers to retry. */ if (root->height == 0) - *((unsigned long *)&to_free->slots[0]) |= + *((unsigned long *)&to_free->slots[0]) = RADIX_TREE_INDIRECT_PTR; radix_tree_node_free(to_free); -- 2.6.2
next prev parent reply other threads:[~2016-03-21 13:22 UTC|newest] Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-21 13:22 [RFC v2] [PATCH 0/10] DAX page fault locking Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-21 13:22 ` [PATCH 01/10] DAX: move RADIX_DAX_ definitions to dax.c Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-21 17:25 ` Matthew Wilcox 2016-03-21 17:25 ` Matthew Wilcox 2016-03-21 13:22 ` Jan Kara [this message] 2016-03-21 13:22 ` [PATCH 02/10] radix-tree: make 'indirect' bit available to exception entries Jan Kara 2016-03-21 17:34 ` Matthew Wilcox 2016-03-21 17:34 ` Matthew Wilcox 2016-03-22 9:12 ` Jan Kara 2016-03-22 9:12 ` Jan Kara 2016-03-22 9:27 ` Matthew Wilcox 2016-03-22 9:27 ` Matthew Wilcox 2016-03-22 10:37 ` Jan Kara 2016-03-22 10:37 ` Jan Kara 2016-03-23 16:41 ` Ross Zwisler 2016-03-23 16:41 ` Ross Zwisler 2016-03-24 12:31 ` Jan Kara 2016-03-24 12:31 ` Jan Kara 2016-03-21 13:22 ` [PATCH 03/10] dax: Remove complete_unwritten argument Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-23 17:12 ` Ross Zwisler 2016-03-23 17:12 ` Ross Zwisler 2016-03-24 12:32 ` Jan Kara 2016-03-24 12:32 ` Jan Kara 2016-03-21 13:22 ` [PATCH 04/10] dax: Fix data corruption for written and mmapped files Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-23 17:39 ` Ross Zwisler 2016-03-23 17:39 ` Ross Zwisler 2016-03-24 12:51 ` Jan Kara 2016-03-24 12:51 ` Jan Kara 2016-03-29 15:17 ` Ross Zwisler 2016-03-29 15:17 ` Ross Zwisler 2016-03-21 13:22 ` [PATCH 05/10] dax: Allow DAX code to replace exceptional entries Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-23 17:52 ` Ross Zwisler 2016-03-23 17:52 ` Ross Zwisler 2016-03-24 10:42 ` Jan Kara 2016-03-24 10:42 ` Jan Kara 2016-03-21 13:22 ` [PATCH 06/10] dax: Remove redundant inode size checks Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-23 21:08 ` Ross Zwisler 2016-03-23 21:08 ` Ross Zwisler 2016-03-21 13:22 ` [PATCH 07/10] dax: Disable huge page handling Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-23 20:50 ` Ross Zwisler 2016-03-23 20:50 ` Ross Zwisler 2016-03-24 12:56 ` Jan Kara 2016-03-24 12:56 ` Jan Kara 2016-03-21 13:22 ` [PATCH 08/10] dax: New fault locking Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-29 21:57 ` Ross Zwisler 2016-03-29 21:57 ` Ross Zwisler 2016-03-31 16:27 ` Jan Kara 2016-03-31 16:27 ` Jan Kara 2016-03-21 13:22 ` [PATCH 09/10] dax: Use radix tree entry lock to protect cow faults Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-21 19:11 ` Matthew Wilcox 2016-03-21 19:11 ` Matthew Wilcox 2016-03-22 7:03 ` Jan Kara 2016-03-22 7:03 ` Jan Kara 2016-03-29 22:18 ` Ross Zwisler 2016-03-29 22:18 ` Ross Zwisler 2016-03-21 13:22 ` [PATCH 10/10] dax: Remove i_mmap_lock protection Jan Kara 2016-03-21 13:22 ` Jan Kara 2016-03-29 22:17 ` Ross Zwisler 2016-03-29 22:17 ` Ross Zwisler 2016-03-21 17:41 ` [RFC v2] [PATCH 0/10] DAX page fault locking Matthew Wilcox 2016-03-21 17:41 ` Matthew Wilcox 2016-03-23 15:09 ` Jan Kara 2016-03-23 15:09 ` Jan Kara 2016-03-23 20:50 ` Matthew Wilcox 2016-03-23 20:50 ` Matthew Wilcox 2016-03-24 10:00 ` Matthew Wilcox 2016-03-24 10:00 ` Matthew Wilcox 2016-03-22 19:32 ` Ross Zwisler 2016-03-22 19:32 ` Ross Zwisler 2016-03-22 21:07 ` Toshi Kani 2016-03-22 21:07 ` Toshi Kani 2016-03-22 21:15 ` Dave Chinner 2016-03-22 21:15 ` Dave Chinner 2016-03-23 9:45 ` Jan Kara 2016-03-23 9:45 ` Jan Kara 2016-03-23 15:11 ` Toshi Kani 2016-03-23 15:11 ` Toshi Kani
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