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
This commit is contained in:
parent
5208386c50
commit
90e775b71a
|
@ -2432,16 +2432,32 @@ do { \
|
|||
#define EXT4_FREECLUSTERS_WATERMARK 0
|
||||
#endif
|
||||
|
||||
/* Update i_disksize. Requires i_mutex to avoid races with truncate */
|
||||
static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
|
||||
{
|
||||
/*
|
||||
* XXX: replace with spinlock if seen contended -bzzz
|
||||
*/
|
||||
WARN_ON_ONCE(S_ISREG(inode->i_mode) &&
|
||||
!mutex_is_locked(&inode->i_mutex));
|
||||
down_write(&EXT4_I(inode)->i_data_sem);
|
||||
if (newsize > EXT4_I(inode)->i_disksize)
|
||||
EXT4_I(inode)->i_disksize = newsize;
|
||||
up_write(&EXT4_I(inode)->i_data_sem);
|
||||
return ;
|
||||
}
|
||||
|
||||
/*
|
||||
* 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 {
|
||||
|
|
|
@ -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
|
||||
|
|
Loading…
Reference in New Issue