The function inserts a memory page to a shmem file under an arbitrary
offset. If there is something at the specified offset (page or swap),
the function fails.
The function will be sued by the next patch.
---
include/linux/shmem_fs.h | 3 ++
mm/shmem.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 30aa0dc..da63308 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -62,4 +62,7 @@ static inline struct page *shmem_read_mapping_page(
mapping_gfp_mask(mapping));
}
+extern int shmem_insert_page(struct inode *inode,
+ pgoff_t index, struct page *page, bool on_lru);
+
#endif
diff --git a/mm/shmem.c b/mm/shmem.c
index 1c44af7..71fac31 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -328,6 +328,74 @@ static void shmem_delete_from_page_cache(struct page
*page, void *radswap)
BUG_ON(error);
}
+int shmem_insert_page(struct inode *inode,
+ pgoff_t index, struct page *page, bool on_lru)
+{
+ 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;
+
+ if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
+ return -EFBIG;
+
+ err = -ENOSPC;
+ if (shmem_acct_block(info->flags))
+ goto out;
+ if (sbinfo->max_blocks) {
+ if (percpu_counter_compare(&sbinfo->used_blocks,
+ sbinfo->max_blocks) >= 0)
+ goto out_unacct;
+ percpu_counter_inc(&sbinfo->used_blocks);
+ }
+
+ if (!on_lru) {
+ SetPageSwapBacked(page);
+ __set_page_locked(page);
+ } else
+ lock_page(page);
+
+ err = mem_cgroup_cache_charge(page, current->mm,
+ gfp & GFP_RECLAIM_MASK);
+ if (err)
+ goto out_unlock;
+ err = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
+ if (!err) {
+ err = shmem_add_to_page_cache(page, mapping, index, gfp, NULL);
+ radix_tree_preload_end();
+ }
+ if (err)
+ goto out_uncharge;
+
+ if (!on_lru)
+ lru_cache_add_anon(page);
+
+ spin_lock(&info->lock);
+ info->alloced++;
+ inode->i_blocks += BLOCKS_PER_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_uncharge:
+ mem_cgroup_uncharge_cache_page(page);
+out_unlock:
+ unlock_page(page);
+ if (sbinfo->max_blocks)
+ percpu_counter_add(&sbinfo->used_blocks, -1);
+out_unacct:
+ shmem_unacct_blocks(info->flags, 1);
+out:
+ return err;
+}
+
/*
* Like find_get_pages, but collecting swap entries as well as pages.
*/
--
1.7.10.4
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