From: Dmitry Monakhov Date: Sat, 29 Sep 2012 04:55:23 +0000 (-0400) Subject: ext4: serialize unlocked dio reads with truncate X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1c9114f9c0f10f58dd7e568a7152025af47b27e5;p=linux-beck.git ext4: serialize unlocked dio reads with truncate Current serialization will works only for DIO which holds i_mutex, but nonlocked DIO following race is possible: dio_nolock_read_task truncate_task ->ext4_setattr() ->inode_dio_wait() ->ext4_ext_direct_IO ->ext4_ind_direct_IO ->__blockdev_direct_IO ->ext4_get_block ->truncate_setsize() ->ext4_truncate() #alloc truncated blocks #to other inode ->submit_io() #INFORMATION LEAK In order to serialize with unlocked DIO reads we have to rearrange wait sequence 1) update i_size first 2) if i_size about to be reduced wait for outstanding DIO requests 3) and only after that truncate inode blocks Reviewed-by: Jan Kara Signed-off-by: Dmitry Monakhov Signed-off-by: "Theodore Ts'o" --- diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index bdd399bc2abf..0bfc63331467 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4283,7 +4283,6 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) } if (attr->ia_valid & ATTR_SIZE) { - inode_dio_wait(inode); if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) { struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); @@ -4332,8 +4331,12 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) } if (attr->ia_valid & ATTR_SIZE) { - if (attr->ia_size != i_size_read(inode)) + if (attr->ia_size != i_size_read(inode)) { truncate_setsize(inode, attr->ia_size); + /* Inode size will be reduced, wait for dio in flight */ + if (orphan) + inode_dio_wait(inode); + } ext4_truncate(inode); }