1) get rid of the actor function pointer in shm as what Kirill did in generic
file operations.

2) add kernel command line option to turn on/off the thp page cache support.

Signed-off-by: Ning Qu <qun...@gmail.com>
---
 mm/huge_memory.c | 27 +++++++++++++++++++++++++++
 mm/shmem.c       |  7 ++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d36bdac..ea79a70 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -711,6 +711,33 @@ out:
 }
 __setup("transparent_hugepage=", setup_transparent_hugepage);
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE
+static int __init setup_transparent_hugepage_pagecache(char *str)
+{
+       int ret = 0;
+       if (!str)
+               goto out;
+       if (!strcmp(str, "on")) {
+               set_bit(TRANSPARENT_HUGEPAGE_PAGECACHE,
+                       &transparent_hugepage_flags);
+               ret = 1;
+       } else if (!strcmp(str, "off")) {
+               clear_bit(TRANSPARENT_HUGEPAGE_PAGECACHE,
+                         &transparent_hugepage_flags);
+               ret = 1;
+       }
+out:
+       if (!ret)
+               printk(KERN_WARNING
+                       "transparent_hugepage_pagecache= cannot parse, "
+                       "ignored\n");
+       return ret;
+}
+
+__setup("transparent_hugepage_pagecache=",
+       setup_transparent_hugepage_pagecache);
+#endif
+
 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 {
        if (likely(vma->vm_flags & VM_WRITE))
diff --git a/mm/shmem.c b/mm/shmem.c
index 391c4eb..77dd90b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1765,7 +1765,8 @@ static unsigned long pos_to_off(struct page *page, loff_t 
pos)
        return pos & ~page_cache_to_mask(page);
 }
 
-static void do_shmem_file_read(struct file *filp, loff_t *ppos, 
read_descriptor_t *desc, read_actor_t actor)
+static void do_shmem_file_read(struct file *filp, loff_t *ppos,
+                               read_descriptor_t *desc)
 {
        struct inode *inode = file_inode(filp);
        gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
@@ -1862,7 +1863,7 @@ static void do_shmem_file_read(struct file *filp, loff_t 
*ppos, read_descriptor_
                 * "pos" here (the actor routine has to update the user buffer
                 * pointers and the remaining count).
                 */
-               ret = actor(desc, page, pos_to_off(page, *ppos), nr);
+               ret = file_read_actor(desc, page, pos_to_off(page, *ppos), nr);
                *ppos += ret;
                index = *ppos >> PAGE_CACHE_SHIFT;
 
@@ -1899,7 +1900,7 @@ static ssize_t shmem_file_aio_read(struct kiocb *iocb,
                if (desc.count == 0)
                        continue;
                desc.error = 0;
-               do_shmem_file_read(filp, ppos, &desc, file_read_actor);
+               do_shmem_file_read(filp, ppos, &desc);
                retval += desc.written;
                if (desc.error) {
                        retval = retval ?: desc.error;
-- 
1.8.4

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