The function inserts a page into a shmem file at a specified offset.
The page can be a regular PAGE_SIZE page or a transparent huge page.
If there is something at the offset (page or swap), the function fails.
The function will be used by the next patch.
Originally-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
---
include/linux/shmem_fs.h | 3 ++
mm/shmem.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 98 insertions(+)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 7a35a6901221..688b92cd4ec7 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -96,6 +96,9 @@ enum sgp_type {
extern int shmem_getpage(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp);
+extern int shmem_insert_page(struct mm_struct *mm, struct inode *inode,
+ pgoff_t index, struct page *page);
+
static inline struct page *shmem_read_mapping_page(
struct address_space *mapping, pgoff_t index)
{
diff --git a/mm/shmem.c b/mm/shmem.c
index bd8840082c94..0a9a2166e51f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -677,6 +677,101 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
BUG_ON(error);
}
+int shmem_insert_page(struct mm_struct *mm, struct inode *inode, pgoff_t index,
+ struct page *page)
+{
+ struct address_space *mapping = inode->i_mapping;
+ struct shmem_inode_info *info = SHMEM_I(inode);
+ struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+ gfp_t gfp = mapping_gfp_mask(mapping);
+ int err;
+ int nr = 1;
+ struct mem_cgroup *memcg;
+ pgoff_t hindex = index;
+ bool on_lru = PageLRU(page);
+
+ if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
+ return -EFBIG;
+
+ if (PageTransHuge(page))
+ nr = HPAGE_PMD_NR;
+ else
+ nr = 1;
+retry:
+ err = 0;
+ if (!shmem_inode_acct_block(inode, nr))
+ err = -ENOSPC;
+ if (err) {
+ int retry = 5;
+
+ /*
+ * Try to reclaim some space by splitting a huge page
+ * beyond i_size on the filesystem.
+ */
+ while (retry--) {
+ int ret;
+
+ ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
+ if (ret == SHRINK_STOP)
+ break;
+ if (ret)
+ goto retry;
+ }
+ goto failed;
+ }
+
+ if (!on_lru) {
+ __SetPageLocked(page);
+ __SetPageSwapBacked(page);
+ } else {
+ lock_page(page);
+ }
+
+ if (PageTransHuge(page))
+ hindex = round_down(index, HPAGE_PMD_NR);
+ else
+ hindex = index;
+
+ __SetPageReferenced(page);
+
+ err = mem_cgroup_try_charge_delay(page, mm, gfp, &memcg,
+ PageTransHuge(page));
+ if (err)
+ goto out_unlock;
+
+ err = shmem_add_to_page_cache(page, mapping, hindex,
+ NULL, gfp & GFP_RECLAIM_MASK);
+ if (err) {
+ mem_cgroup_cancel_charge(page, memcg,
+ PageTransHuge(page));
+ goto out_unlock;
+ }
+ mem_cgroup_commit_charge(page, memcg, on_lru,
+ PageTransHuge(page));
+
+ if (!on_lru)
+ lru_cache_add_anon(page);
+
+ spin_lock(&info->lock);
+ info->alloced += compound_nr(page);
+ inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
+ shmem_recalc_inode(inode);
+ spin_unlock(&info->lock);
+
+ flush_dcache_page(page);
+ SetPageUptodate(page);
+ set_page_dirty(page);
+
+ unlock_page(page);
+ return 0;
+
+out_unlock:
+ unlock_page(page);
+ shmem_inode_unacct_blocks(inode, nr);
+failed:
+ return err;
+}
+
/*
* Remove swap entry from page cache, free the swap and its page cache.
*/
--
2.13.3
