tmpfs: mem_cgroup charge fault to vm_mm not current mm

Although shmem_fault() has been careful to count a major fault to vm_mm,
shmem_getpage_gfp() has been careless in charging a remote access fault
to current->mm owner's memcg instead of to vma->vm_mm owner's memcg:
that is inconsistent with all the mem_cgroup charging on remote access
faults in mm/memory.c.

Fix it by passing fault_mm along with fault_type to
shmem_get_page_gfp(); but in that case, now knowing the right mm, it's
better for it to handle the PGMAJFAULT updates itself.

And let's keep this clutter out of most callers' way: change the common
shmem_getpage() wrapper to hide fault_mm and fault_type as well as gfp.

Signed-off-by: Andres Lagar-Cavilla <andreslc@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Ning Qu <quning@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 27 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 6d2de2c1bf11..e418a995427d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -121,13 +121,14 @@ static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
                                 struct shmem_inode_info *info, pgoff_t index);
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
-        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
+                struct page **pagep, enum sgp_type sgp,
+                gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
 
 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
-        struct page **pagep, enum sgp_type sgp, int *fault_type)
+                struct page **pagep, enum sgp_type sgp)
 {
         return shmem_getpage_gfp(inode, index, pagep, sgp,
-                        mapping_gfp_mask(inode->i_mapping), fault_type);
+                mapping_gfp_mask(inode->i_mapping), NULL, NULL);
 }
 
 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
@@ -527,7 +528,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 
         if (partial_start) {
                 struct page *page = NULL;
-                shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
+                shmem_getpage(inode, start - 1, &page, SGP_READ);
                 if (page) {
                         unsigned int top = PAGE_SIZE;
                         if (start > end) {
@@ -542,7 +543,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
         }
         if (partial_end) {
                 struct page *page = NULL;
-                shmem_getpage(inode, end, &page, SGP_READ, NULL);
+                shmem_getpage(inode, end, &page, SGP_READ);
                 if (page) {
                         zero_user_segment(page, 0, partial_end);
                         set_page_dirty(page);
@@ -1115,14 +1116,19 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
  *
  * If we allocate a new one we do not mark it dirty. That's up to the
  * vm. If we swap it in we mark it dirty since we also free the swap
- * entry since a page cannot live in both the swap and page cache
+ * entry since a page cannot live in both the swap and page cache.
+ *
+ * fault_mm and fault_type are only supplied by shmem_fault:
+ * otherwise they are NULL.
  */
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
-        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
+        struct page **pagep, enum sgp_type sgp, gfp_t gfp,
+        struct mm_struct *fault_mm, int *fault_type)
 {
         struct address_space *mapping = inode->i_mapping;
         struct shmem_inode_info *info;
         struct shmem_sb_info *sbinfo;
+        struct mm_struct *charge_mm;
         struct mem_cgroup *memcg;
         struct page *page;
         swp_entry_t swap;
@@ -1168,14 +1174,19 @@ repeat:
          */
         info = SHMEM_I(inode);
         sbinfo = SHMEM_SB(inode->i_sb);
+        charge_mm = fault_mm ? : current->mm;
 
         if (swap.val) {
                 /* Look it up and read it in.. */
                 page = lookup_swap_cache(swap);
                 if (!page) {
-                        /* here we actually do the io */
-                        if (fault_type)
+                        /* Or update major stats only when swapin succeeds?? */
+                        if (fault_type) {
                                 *fault_type |= VM_FAULT_MAJOR;
+                                count_vm_event(PGMAJFAULT);
+                                mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
+                        }
+                        /* Here we actually start the io */
                         page = shmem_swapin(swap, gfp, info, index);
                         if (!page) {
                                 error = -ENOMEM;
@@ -1202,7 +1213,7 @@ repeat:
                                 goto failed;
                 }
 
-                error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg,
+                error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
                                 false);
                 if (!error) {
                         error = shmem_add_to_page_cache(page, mapping, index,
@@ -1263,7 +1274,7 @@ repeat:
                 if (sgp == SGP_WRITE)
                         __SetPageReferenced(page);
 
-                error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg,
+                error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
                                 false);
                 if (error)
                         goto decused;
@@ -1352,6 +1363,7 @@ unlock:
 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         struct inode *inode = file_inode(vma->vm_file);
+        gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
         int error;
         int ret = VM_FAULT_LOCKED;
 
@@ -1413,14 +1425,10 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
                 spin_unlock(&inode->i_lock);
         }
 
-        error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
+        error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, SGP_CACHE,
+                                  gfp, vma->vm_mm, &ret);
         if (error)
                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
-
-        if (ret & VM_FAULT_MAJOR) {
-                count_vm_event(PGMAJFAULT);
-                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
-        }
         return ret;
 }
 
@@ -1567,7 +1575,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
                         return -EPERM;
         }
 
-        return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
+        return shmem_getpage(inode, index, pagep, SGP_WRITE);
 }
 
 static int
@@ -1633,7 +1641,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
                                 break;
                 }
 
-                error = shmem_getpage(inode, index, &page, sgp, NULL);
+                error = shmem_getpage(inode, index, &page, sgp);
                 if (error) {
                         if (error == -EINVAL)
                                 error = 0;
@@ -1749,7 +1757,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
         error = 0;
 
         while (spd.nr_pages < nr_pages) {
-                error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
+                error = shmem_getpage(inode, index, &page, SGP_CACHE);
                 if (error)
                         break;
                 unlock_page(page);
@@ -1771,8 +1779,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
                 page = spd.pages[page_nr];
 
                 if (!PageUptodate(page) || page->mapping != mapping) {
-                        error = shmem_getpage(inode, index, &page,
-                                                        SGP_CACHE, NULL);
+                        error = shmem_getpage(inode, index, &page, SGP_CACHE);
                         if (error)
                                 break;
                         unlock_page(page);
@@ -2215,8 +2222,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
                         error = -ENOMEM;
                 else
-                        error = shmem_getpage(inode, index, &page, SGP_FALLOC,
-                                                                        NULL);
+                        error = shmem_getpage(inode, index, &page, SGP_FALLOC);
                 if (error) {
                         /* Remove the !PageUptodate pages we added */
                         shmem_undo_range(inode,
@@ -2534,7 +2540,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
                 inode->i_op = &shmem_short_symlink_operations;
         } else {
                 inode_nohighmem(inode);
-                error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
+                error = shmem_getpage(inode, 0, &page, SGP_WRITE);
                 if (error) {
                         iput(inode);
                         return error;
@@ -2575,7 +2581,7 @@ static const char *shmem_get_link(struct dentry *dentry,
                         return ERR_PTR(-ECHILD);
                 }
         } else {
-                error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
+                error = shmem_getpage(inode, 0, &page, SGP_READ);
                 if (error)
                         return ERR_PTR(error);
                 unlock_page(page);
@@ -3479,7 +3485,8 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
         int error;
 
         BUG_ON(mapping->a_ops != &shmem_aops);
-        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
+        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
+                                  gfp, NULL, NULL);
         if (error)
                 page = ERR_PTR(error);
         else