ping? Is these two patches can be merged into linux-4.19? :'(
Thanks, Gao Xiang
On 2019/2/26 20:43, Gao Xiang wrote:
Hi Matthew,
On 2019/2/26 13:14, Gao Xiang wrote:
From: Matthew Wilcox willy@infradead.org
commit 3159f943aafdbacb2f94c38fdaadabf2bbde2a14 upstream.
Introduce xarray value entries and tagged pointers to replace radix tree exceptional entries. This is a slight change in encoding to allow the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a value entry). It is also a change in emphasis; exceptional entries are intimidating and different. As the comment explains, you can choose to store values or pointers in the xarray and they are both first-class citizens.
Signed-off-by: Matthew Wilcox willy@infradead.org Reviewed-by: Josef Bacik jbacik@fb.com [ take the minimum subset of tagged pointer support only. ] Cc: Matthew Wilcox willy@infradead.org Signed-off-by: Gao Xiang gaoxiang25@huawei.com
change log v2:
- fix tagged pointer apis to make it work properly pointed out by Matthew;
Is this version ok? Could you kindly give an "Acked-by" tag for this patch?
The following patch is important for erofs, I'd like to backport it ASAP... staging: erofs: fix race when the managed cache is enabled
It will be of great help. Thanks in advance!
Thanks, Gao Xiang
drivers/staging/erofs/utils.c | 18 +++++---------- include/linux/xarray.h | 52 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 12 deletions(-)
diff --git a/drivers/staging/erofs/utils.c b/drivers/staging/erofs/utils.c index 595cf90af9bb..bdee9bd09f11 100644 --- a/drivers/staging/erofs/utils.c +++ b/drivers/staging/erofs/utils.c @@ -35,7 +35,6 @@ static atomic_long_t erofs_global_shrink_cnt; #ifdef CONFIG_EROFS_FS_ZIP -/* radix_tree and the future XArray both don't use tagptr_t yet */ struct erofs_workgroup *erofs_find_workgroup( struct super_block *sb, pgoff_t index, bool *tag) { @@ -47,9 +46,8 @@ struct erofs_workgroup *erofs_find_workgroup( rcu_read_lock(); grp = radix_tree_lookup(&sbi->workstn_tree, index); if (grp != NULL) {
*tag = radix_tree_exceptional_entry(grp);grp = (void *)((unsigned long)grp &~RADIX_TREE_EXCEPTIONAL_ENTRY);
*tag = xa_pointer_tag(grp);grp = xa_untag_pointer(grp);if (erofs_workgroup_get(grp, &oldcount)) { /* prefer to relax rcu read side */ @@ -83,9 +81,7 @@ int erofs_register_workgroup(struct super_block *sb, sbi = EROFS_SB(sb); erofs_workstn_lock(sbi);
- if (tag)
grp = (void *)((unsigned long)grp |1UL << RADIX_TREE_EXCEPTIONAL_SHIFT);
- grp = xa_tag_pointer(grp, tag);
err = radix_tree_insert(&sbi->workstn_tree, grp->index, grp); @@ -131,9 +127,7 @@ unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi, for (i = 0; i < found; ++i) { int cnt;
struct erofs_workgroup *grp = (void *)((unsigned long)batch[i] &~RADIX_TREE_EXCEPTIONAL_ENTRY);
struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);first_index = grp->index + 1; @@ -150,8 +144,8 @@ unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi, #endif continue;
if (radix_tree_delete(&sbi->workstn_tree,grp->index) != grp) {
if (xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,grp->index)) != grp) {#ifdef EROFS_FS_HAS_MANAGED_CACHE skip: erofs_workgroup_unfreeze(grp, 1); diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 2dfc8006fe64..51ae9779d08b 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -9,6 +9,58 @@ #include <linux/spinlock.h> +/**
- xa_tag_pointer() - Create an XArray entry for a tagged pointer.
- @p: Plain pointer.
- @tag: Tag value (0 or 1).
- If the user of the XArray prefers, they can tag their pointers instead
- of storing value entries. Two tags are available (0 and 1).
- These are distinct from the xa_mark_t as they are not replicated up
- through the array and cannot be searched for.
- Context: Any context.
- Return: An XArray entry.
- */
+static inline void *xa_tag_pointer(void *p, unsigned long tag) +{
- if (__builtin_constant_p(tag))
BUILD_BUG_ON(tag > 1);- else
BUG_ON(tag > 1);- return (void *)((unsigned long)p | (tag << 1));
+}
+/**
- xa_untag_pointer() - Turn an XArray entry into a plain pointer.
- @entry: XArray entry.
- If you have stored a tagged pointer in the XArray, call this function
- to get the untagged version of the pointer.
- Context: Any context.
- Return: A pointer.
- */
+static inline void *xa_untag_pointer(void *entry) +{
- return (void *)((unsigned long)entry & ~3UL);
+}
+/**
- xa_pointer_tag() - Get the tag stored in an XArray entry.
- @entry: XArray entry.
- If you have stored a tagged pointer in the XArray, call this function
- to get the tag of that pointer.
- Context: Any context.
- Return: A tag.
- */
+static inline unsigned int xa_pointer_tag(void *entry) +{
- return ((unsigned long)entry & 3UL) >> 1;
+}
#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock) #define xa_lock(xa) spin_lock(&(xa)->xa_lock) #define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)