ping? ...
On 2019/3/4 13:13, Gao Xiang wrote:
> 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@xxxxxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxxxxx>
>>> Reviewed-by: Josef Bacik <jbacik@xxxxxx>
>>> [ take the minimum subset of tagged pointer support only. ]
>>> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
>>> Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
>>> ---
>>> 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)
>>>
