1 files changed, 13 insertions, 1 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 4ae47f54c822..c919ed578f0a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -80,6 +80,7 @@
 enum sgp_type {
         SGP_READ,       /* don't exceed i_size, don't allocate page */
         SGP_CACHE,      /* don't exceed i_size, may allocate page */
+        SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
         SGP_WRITE,      /* may exceed i_size, may allocate page */
 };
 
@@ -1333,6 +1334,8 @@ repeat:
                 clear_highpage(filepage);
                 flush_dcache_page(filepage);
                 SetPageUptodate(filepage);
+                if (sgp == SGP_DIRTY)
+                        set_page_dirty(filepage);
         }
 done:
         *pagep = filepage;
@@ -1518,6 +1521,15 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_
         struct inode *inode = filp->f_path.dentry->d_inode;
         struct address_space *mapping = inode->i_mapping;
         unsigned long index, offset;
+        enum sgp_type sgp = SGP_READ;
+
+        /*
+         * Might this read be for a stacking filesystem?  Then when reading
+         * holes of a sparse file, we actually need to allocate those pages,
+         * and even mark them dirty, so it cannot exceed the max_blocks limit.
+         */
+        if (segment_eq(get_fs(), KERNEL_DS))
+                sgp = SGP_DIRTY;
 
         index = *ppos >> PAGE_CACHE_SHIFT;
         offset = *ppos & ~PAGE_CACHE_MASK;
@@ -1536,7 +1548,7 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_
                                 break;
                 }
 
-                desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
+                desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
                 if (desc->error) {
                         if (desc->error == -EINVAL)
                                 desc->error = 0;