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SubjectRe: [PATCH v2 07/20] mm, hugetlb: unify region structure handling
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Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Currently, to track a reserved and allocated region, we use two different
> ways for MAP_SHARED and MAP_PRIVATE. For MAP_SHARED, we use
> address_mapping's private_list and, for MAP_PRIVATE, we use a resv_map.
> Now, we are preparing to change a coarse grained lock which protect
> a region structure to fine grained lock, and this difference hinder it.
> So, before changing it, unify region structure handling.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

As mentioned earlier kref_put is confusing because we always have
reference count == 1 , otherwise

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index a3f868a..9bf2c4a 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -366,7 +366,12 @@ static void truncate_hugepages(struct inode *inode, loff_t lstart)
>
> static void hugetlbfs_evict_inode(struct inode *inode)
> {
> + struct resv_map *resv_map;
> +
> truncate_hugepages(inode, 0);
> + resv_map = (struct resv_map *)inode->i_mapping->private_data;
> + if (resv_map)
> + kref_put(&resv_map->refs, resv_map_release);
> clear_inode(inode);
> }
>
> @@ -468,6 +473,11 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
> umode_t mode, dev_t dev)
> {
> struct inode *inode;
> + struct resv_map *resv_map;
> +
> + resv_map = resv_map_alloc();
> + if (!resv_map)
> + return NULL;
>
> inode = new_inode(sb);
> if (inode) {
> @@ -477,7 +487,7 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
> inode->i_mapping->a_ops = &hugetlbfs_aops;
> inode->i_mapping->backing_dev_info =&hugetlbfs_backing_dev_info;
> inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> - INIT_LIST_HEAD(&inode->i_mapping->private_list);
> + inode->i_mapping->private_data = resv_map;
> info = HUGETLBFS_I(inode);
> /*
> * The policy is initialized here even if we are creating a
> @@ -507,7 +517,9 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
> break;
> }
> lockdep_annotate_inode_mutex_key(inode);
> - }
> + } else
> + kref_put(&resv_map->refs, resv_map_release);
> +
> return inode;
> }
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 6b4890f..2677c07 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -5,6 +5,8 @@
> #include <linux/fs.h>
> #include <linux/hugetlb_inline.h>
> #include <linux/cgroup.h>
> +#include <linux/list.h>
> +#include <linux/kref.h>
>
> struct ctl_table;
> struct user_struct;
> @@ -22,6 +24,13 @@ struct hugepage_subpool {
> long max_hpages, used_hpages;
> };
>
> +struct resv_map {
> + struct kref refs;
> + struct list_head regions;
> +};
> +extern struct resv_map *resv_map_alloc(void);
> +void resv_map_release(struct kref *ref);
> +
> extern spinlock_t hugetlb_lock;
> extern int hugetlb_max_hstate __read_mostly;
> #define for_each_hstate(h) \
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3f834f1..8751e2c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -375,12 +375,7 @@ static void set_vma_private_data(struct vm_area_struct *vma,
> vma->vm_private_data = (void *)value;
> }
>
> -struct resv_map {
> - struct kref refs;
> - struct list_head regions;
> -};
> -
> -static struct resv_map *resv_map_alloc(void)
> +struct resv_map *resv_map_alloc(void)
> {
> struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
> if (!resv_map)
> @@ -392,7 +387,7 @@ static struct resv_map *resv_map_alloc(void)
> return resv_map;
> }
>
> -static void resv_map_release(struct kref *ref)
> +void resv_map_release(struct kref *ref)
> {
> struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
>
> @@ -1092,8 +1087,9 @@ static long vma_needs_reservation(struct hstate *h,
>
> if (vma->vm_flags & VM_MAYSHARE) {
> pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> - return region_chg(&inode->i_mapping->private_list,
> - idx, idx + 1);
> + struct resv_map *resv = inode->i_mapping->private_data;
> +
> + return region_chg(&resv->regions, idx, idx + 1);
>
> } else if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
> return 1;
> @@ -1117,7 +1113,9 @@ static void vma_commit_reservation(struct hstate *h,
>
> if (vma->vm_flags & VM_MAYSHARE) {
> pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> - region_add(&inode->i_mapping->private_list, idx, idx + 1);
> + struct resv_map *resv = inode->i_mapping->private_data;
> +
> + region_add(&resv->regions, idx, idx + 1);
>
> } else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
> pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> @@ -3074,6 +3072,7 @@ int hugetlb_reserve_pages(struct inode *inode,
> long ret, chg;
> struct hstate *h = hstate_inode(inode);
> struct hugepage_subpool *spool = subpool_inode(inode);
> + struct resv_map *resv_map;
>
> /*
> * Only apply hugepage reservation if asked. At fault time, an
> @@ -3089,10 +3088,13 @@ int hugetlb_reserve_pages(struct inode *inode,
> * to reserve the full area even if read-only as mprotect() may be
> * called to make the mapping read-write. Assume !vma is a shm mapping
> */
> - if (!vma || vma->vm_flags & VM_MAYSHARE)
> - chg = region_chg(&inode->i_mapping->private_list, from, to);
> - else {
> - struct resv_map *resv_map = resv_map_alloc();
> + if (!vma || vma->vm_flags & VM_MAYSHARE) {
> + resv_map = inode->i_mapping->private_data;
> +
> + chg = region_chg(&resv_map->regions, from, to);
> +
> + } else {
> + resv_map = resv_map_alloc();
> if (!resv_map)
> return -ENOMEM;
>
> @@ -3135,7 +3137,7 @@ int hugetlb_reserve_pages(struct inode *inode,
> * else has to be done for private mappings here
> */
> if (!vma || vma->vm_flags & VM_MAYSHARE)
> - region_add(&inode->i_mapping->private_list, from, to);
> + region_add(&resv_map->regions, from, to);
> return 0;
> out_err:
> if (vma)
> @@ -3146,9 +3148,12 @@ out_err:
> void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
> {
> struct hstate *h = hstate_inode(inode);
> - long chg = region_truncate(&inode->i_mapping->private_list, offset);
> + struct resv_map *resv_map = inode->i_mapping->private_data;
> + long chg = 0;
> struct hugepage_subpool *spool = subpool_inode(inode);
>
> + if (resv_map)
> + chg = region_truncate(&resv_map->regions, offset);
> spin_lock(&inode->i_lock);
> inode->i_blocks -= (blocks_per_huge_page(h) * freed);
> spin_unlock(&inode->i_lock);
> --
> 1.7.9.5



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