[PATCH 3.12 118/182] ext4: move ext4_update_i_disksize() into mpage_map_and_submit_extent()

Jiri Slaby
2014-05-13T10:15:20Z

From: Theodore Ts'o <tytso@mit.edu>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 622cad1325e404598fe3b148c3fa640dbaabc235 upstream.

The function ext4_update_i_disksize() is used in only one place, in
the function mpage_map_and_submit_extent(). Move its code to simplify
the code paths, and also move the call to ext4_mark_inode_dirty() into
the i_data_sem's critical region, to be consistent with all of the
other places where we update i_disksize. That way, we also keep the
raw_inode's i_disksize protected, to avoid the following race:

CPU #1 CPU #2

down_write(&i_data_sem)
Modify i_disk_size
up_write(&i_data_sem)
down_write(&i_data_sem)
Modify i_disk_size
Copy i_disk_size to on-disk inode
up_write(&i_data_sem)
Copy i_disk_size to on-disk inode

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/ext4/ext4.h | 17 -----------------
fs/ext4/inode.c | 16 +++++++++++++---
2 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a9d2bf941066..1e25d6b57bc5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2445,23 +2445,6 @@ static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
up_write(&EXT4_I(inode)->i_data_sem);
}

-/*
- * Update i_disksize after writeback has been started. Races with truncate
- * are avoided by checking i_size under i_data_sem.
- */
-static inline void ext4_wb_update_i_disksize(struct inode *inode, loff_t newsize)
-{
- loff_t i_size;
-
- down_write(&EXT4_I(inode)->i_data_sem);
- i_size = i_size_read(inode);
- if (newsize > i_size)
- newsize = i_size;
- if (newsize > EXT4_I(inode)->i_disksize)
- EXT4_I(inode)->i_disksize = newsize;
- up_write(&EXT4_I(inode)->i_data_sem);
-}
-
struct ext4_group_info {
unsigned long bb_state;
struct rb_root bb_free_root;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8fdf99bf18d6..ea9793d8a77f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2233,13 +2233,23 @@ static int mpage_map_and_submit_extent(handle_t *handle,
return err;
} while (map->m_len);

- /* Update on-disk size after IO is submitted */
+ /*
+ * Update on-disk size after IO is submitted. Races with
+ * truncate are avoided by checking i_size under i_data_sem.
+ */
disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT;
if (disksize > EXT4_I(inode)->i_disksize) {
int err2;
-
- ext4_wb_update_i_disksize(inode, disksize);
+ loff_t i_size;
+
+ down_write(&EXT4_I(inode)->i_data_sem);
+ i_size = i_size_read(inode);
+ if (disksize > i_size)
+ disksize = i_size;
+ if (disksize > EXT4_I(inode)->i_disksize)
+ EXT4_I(inode)->i_disksize = disksize;
err2 = ext4_mark_inode_dirty(handle, inode);
+ up_write(&EXT4_I(inode)->i_data_sem);
if (err2)
ext4_error(inode->i_sb,
"Failed to mark inode %lu dirty",
--
1.9.3