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hugetlbfs: always use address space in inode for resv_map pointer

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Continuing discussion about 58b6e5e8f1 ("hugetlbfs: fix memory leak for
resv_map") brought up the issue that inode->i_mapping may not point to the
address space embedded within the inode at inode eviction time.  The
hugetlbfs truncate routine handles this by explicitly using inode->i_data.
However, code cleaning up the resv_map will still use the address space
pointed to by inode->i_mapping.  Luckily, private_data is NULL for address
spaces in all such cases today but, there is no guarantee this will
continue.

Change all hugetlbfs code getting a resv_map pointer to explicitly get it
from the address space embedded within the inode.  In addition, add more
comments in the code to indicate why this is being done.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Kravetz <[email protected]>
Reported-by: Yufen Yu <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mike Kravetz 2019-05-13 17:22:55 -07:00 • committed by Linus Torvalds
commit f27a5136f7
2 changed files with 27 additions and 3 deletions
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19
mm/hugetlb.c
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@ -740,7 +740,15 @@ void resv_map_release(struct kref *ref)
static inline struct resv_map *inode_resv_map(struct inode *inode)
{
return inode->i_mapping->private_data;
/*
* At inode evict time, i_mapping may not point to the original
* address space within the inode. This original address space
* contains the pointer to the resv_map. So, always use the
* address space embedded within the inode.
* The VERY common case is inode->mapping == &inode->i_data but,
* this may not be true for device special inodes.
*/
return (struct resv_map *)(&inode->i_data)->private_data;
}
static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
@ -4518,6 +4526,11 @@ int hugetlb_reserve_pages(struct inode *inode,
* called to make the mapping read-write. Assume !vma is a shm mapping
*/
if (!vma || vma->vm_flags & VM_MAYSHARE) {
/*
* resv_map can not be NULL as hugetlb_reserve_pages is only
* called for inodes for which resv_maps were created (see
* hugetlbfs_get_inode).
*/
resv_map = inode_resv_map(inode);
chg = region_chg(resv_map, from, to);
@ -4609,6 +4622,10 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
struct hugepage_subpool *spool = subpool_inode(inode);
long gbl_reserve;
/*
* Since this routine can be called in the evict inode path for all
* hugetlbfs inodes, resv_map could be NULL.
*/
if (resv_map) {
chg = region_del(resv_map, start, end);
/*