[3.13.y.z extended stable] Patch "ext4: move ext4_update_i_disksize() into mpage_map_and_submit_extent()" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Tue Jun 10 18:46:30 UTC 2014


This is a note to let you know that I have just added a patch titled

    ext4: move ext4_update_i_disksize() into mpage_map_and_submit_extent()

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From aed2bf36a110adf319900de09e2a7558c7738d4c Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso at mit.edu>
Date: Fri, 11 Apr 2014 10:35:17 -0400
Subject: ext4: move ext4_update_i_disksize() into
 mpage_map_and_submit_extent()

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 at mit.edu>
Reviewed-by: Jan Kara <jack at suse.cz>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 d3a534f..3a603a8 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2462,23 +2462,6 @@ 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 8ccbe9a..4fafd09 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2242,13 +2242,23 @@ 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",
--
1.9.1





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