diff options
| author | Jan Kara <jack@suse.cz> | 2013-08-17 10:09:31 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-08-17 10:09:31 -0400 |
| commit | 90e775b71ac4e685898c7995756fe58c135adaa6 (patch) | |
| tree | e7e84b7990ad61717808830726b0fce4e9c0464a /fs/ext4/inode.c | |
| parent | 5208386c501276df18fee464e21d3c58d2d79517 (diff) | |
ext4: fix lost truncate due to race with writeback
The following race can lead to a loss of i_disksize update from truncate
thus resulting in a wrong inode size if the inode size isn't updated
again before inode is reclaimed:
ext4_setattr() mpage_map_and_submit_extent()
EXT4_I(inode)->i_disksize = attr->ia_size;
... ...
disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT
/* False because i_size isn't
* updated yet */
if (disksize > i_size_read(inode))
/* True, because i_disksize is
* already truncated */
if (disksize > EXT4_I(inode)->i_disksize)
/* Overwrite i_disksize
* update from truncate */
ext4_update_i_disksize()
i_size_write(inode, attr->ia_size);
For other places updating i_disksize such race cannot happen because
i_mutex prevents these races. Writeback is the only place where we do
not hold i_mutex and we cannot grab it there because of lock ordering.
We fix the race by doing both i_disksize and i_size update in truncate
atomically under i_data_sem and in mpage_map_and_submit_extent() we move
the check against i_size under i_data_sem as well.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/ext4/inode.c')
| -rw-r--r-- | fs/ext4/inode.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 38f430119fef..fc4051eb4e0f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2237,12 +2237,10 @@ static int mpage_map_and_submit_extent(handle_t *handle, /* Update on-disk size after IO is submitted */ disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT; - if (disksize > i_size_read(inode)) - disksize = i_size_read(inode); if (disksize > EXT4_I(inode)->i_disksize) { int err2; - ext4_update_i_disksize(inode, disksize); + ext4_wb_update_i_disksize(inode, disksize); err2 = ext4_mark_inode_dirty(handle, inode); if (err2) ext4_error(inode->i_sb, @@ -4627,18 +4625,27 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) error = ext4_orphan_add(handle, inode); orphan = 1; } + down_write(&EXT4_I(inode)->i_data_sem); EXT4_I(inode)->i_disksize = attr->ia_size; rc = ext4_mark_inode_dirty(handle, inode); if (!error) error = rc; + /* + * We have to update i_size under i_data_sem together + * with i_disksize to avoid races with writeback code + * running ext4_wb_update_i_disksize(). + */ + if (!error) + i_size_write(inode, attr->ia_size); + up_write(&EXT4_I(inode)->i_data_sem); ext4_journal_stop(handle); if (error) { ext4_orphan_del(NULL, inode); goto err_out; } - } + } else + i_size_write(inode, attr->ia_size); - i_size_write(inode, attr->ia_size); /* * Blocks are going to be removed from the inode. Wait * for dio in flight. Temporarily disable |