move-ext4_update_i_disksize-into-mpage_map_and_submit_extent

   1 ext4: move ext4_update_i_disksize() into mpage_map_and_submit_extent()
   2
   3 The function ext4_update_i_disksize() is used in only one place, in
   4 the function mpage_map_and_submit_extent().  Move its code to simplify
   5 the code paths, and also move the call to ext4_mark_inode_dirty() into
   6 the i_data_sem's critical region, to be consistent with all of the
   7 other places where we update i_disksize.  That way, we also keep the
   8 raw_inode's i_disksize protected, to avoid the following race:
   9
  10       CPU #1                                 CPU #2
  11
  12    down_write(&i_data_sem)
  13    Modify i_disk_size
  14    up_write(&i_data_sem)
  15                                         down_write(&i_data_sem)
  16                                         Modify i_disk_size
  17                                         Copy i_disk_size to on-disk inode
  18                                         up_write(&i_data_sem)
  19    Copy i_disk_size to on-disk inode
  20
  21 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  22 Reviewed-by: Jan Kara <jack@suse.cz>
  23 Cc: stable@vger.kernel.org
  24 ---
  25  fs/ext4/ext4.h  | 17 -----------------
  26  fs/ext4/inode.c | 16 +++++++++++++---
  27  2 files changed, 13 insertions(+), 20 deletions(-)
  28
  29 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
  30 index f1c65dc..66946aa 100644
  31 --- a/fs/ext4/ext4.h
  32 +++ b/fs/ext4/ext4.h
  33 @@ -2466,23 +2466,6 @@ static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
  34         up_write(&EXT4_I(inode)->i_data_sem);
  35  }
  36
  37 -/*
  38 - * Update i_disksize after writeback has been started. Races with truncate
  39 - * are avoided by checking i_size under i_data_sem.
  40 - */
  41 -static inline void ext4_wb_update_i_disksize(struct inode *inode, loff_t newsize)
  42 -{
  43 -       loff_t i_size;
  44 -
  45 -       down_write(&EXT4_I(inode)->i_data_sem);
  46 -       i_size = i_size_read(inode);
  47 -       if (newsize > i_size)
  48 -               newsize = i_size;
  49 -       if (newsize > EXT4_I(inode)->i_disksize)
  50 -               EXT4_I(inode)->i_disksize = newsize;
  51 -       up_write(&EXT4_I(inode)->i_data_sem);
  52 -}
  53 -
  54  struct ext4_group_info {
  55         unsigned long   bb_state;
  56         struct rb_root  bb_free_root;
  57 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  58 index 7b93df9..f023f0c 100644
  59 --- a/fs/ext4/inode.c
  60 +++ b/fs/ext4/inode.c
  61 @@ -2247,13 +2247,23 @@ static int mpage_map_and_submit_extent(handle_t *handle,
  62                         return err;
  63         } while (map->m_len);
  64
  65 -       /* Update on-disk size after IO is submitted */
  66 +       /*
  67 +        * Update on-disk size after IO is submitted.  Races with
  68 +        * truncate are avoided by checking i_size under i_data_sem.
  69 +        */
  70         disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT;
  71         if (disksize > EXT4_I(inode)->i_disksize) {
  72                 int err2;
  73 -
  74 -               ext4_wb_update_i_disksize(inode, disksize);
  75 +               loff_t i_size;
  76 +
  77 +               down_write(&EXT4_I(inode)->i_data_sem);
  78 +               i_size = i_size_read(inode);
  79 +               if (disksize > i_size)
  80 +                       disksize = i_size;
  81 +               if (disksize > EXT4_I(inode)->i_disksize)
  82 +                       EXT4_I(inode)->i_disksize = disksize;
  83                 err2 = ext4_mark_inode_dirty(handle, inode);
  84 +               up_write(&EXT4_I(inode)->i_data_sem);
  85                 if (err2)
  86                         ext4_error(inode->i_sb,
  87                                    "Failed to mark inode %lu dirty",