3.16.60-rc1 review patch. If anyone has any objections, please let me know.
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From: Eryu Guan guaneryu@gmail.com
commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream.
i_disksize update should be protected by i_data_sem, by either taking the lock explicitly or by using ext4_update_i_disksize() helper. But the i_disksize updates in ext4_direct_IO_write() are not protected at all, which may be racing with i_disksize updates in writeback path in delalloc buffer write path.
This is found by code inspection, and I didn't hit any i_disksize corruption due to this bug. Thanks to Jan Kara for catching this bug and suggesting the fix!
Reported-by: Jan Kara jack@suse.cz Suggested-by: Jan Kara jack@suse.cz Signed-off-by: Eryu Guan guaneryu@gmail.com Signed-off-by: Theodore Ts'o tytso@mit.edu [bwh: Backported to 3.16: The relevant code is in ext4_ind_direct_IO()] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -649,7 +649,6 @@ ssize_t ext4_ind_direct_IO(int rw, struc { struct file *file = iocb->ki_filp; struct inode *inode = file->f_mapping->host; - struct ext4_inode_info *ei = EXT4_I(inode); handle_t *handle; ssize_t ret; int orphan = 0; @@ -672,7 +671,7 @@ ssize_t ext4_ind_direct_IO(int rw, struc goto out; } orphan = 1; - ei->i_disksize = inode->i_size; + ext4_update_i_disksize(inode, inode->i_size); ext4_journal_stop(handle); } } @@ -731,7 +730,7 @@ locked: if (ret > 0) { loff_t end = offset + ret; if (end > inode->i_size) { - ei->i_disksize = end; + ext4_update_i_disksize(inode, end); i_size_write(inode, end); /* * We're going to return a positive `ret'