On Thu 19-08-21 14:57:04, Zhang Yi wrote:
> In ext4_get_inode_loc(), we may skip IO and get an zero && uptodate
> inode buffer when the inode monopolize an inode block for performance
> reason. For most cases, ext4_mark_iloc_dirty() will fill the inode
> buffer to make it fine, but we could miss this call if something bad
> happened. Finally, __ext4_get_inode_loc_noinmem() may probably get an
> empty inode buffer and trigger ext4 error.
>
> For example, if we remove a nonexistent xattr on inode A,
> ext4_xattr_set_handle() will return ENODATA before invoking
> ext4_mark_iloc_dirty(), it will left an uptodate but zero buffer. We
> will get checksum error message in ext4_iget() when getting inode again.
>
> EXT4-fs error (device sda): ext4_lookup:1784: inode #131074: comm cat: iget: checksum invalid
>
> Even worse, if we allocate another inode B at the same inode block, it
> will corrupt the inode A on disk when write back inode B.
>
> So this patch postpone the init and mark buffer uptodate logic until
> before filling correct inode data in ext4_do_update_inode() if skip read
> I/O, ensure the buffer is real uptodate.
>
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Looks good. Just some language fixes below. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext4/inode.c | 26 +++++++++++++++++++++++---
> 1 file changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d0d7a5295bf9..02d910c9d8f1 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4367,9 +4367,11 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
> }
> brelse(bitmap_bh);
> if (i == start + inodes_per_block) {
> - /* all other inodes are free, so skip I/O */
> - memset(bh->b_data, 0, bh->b_size);
> - set_buffer_uptodate(bh);
> + /*
> + * All other inodes are free, skip I/O. Return
> + * un-inited buffer (which is postponed until
I'd repharse this sentence as: Return uninitialized buffer immediately,
initialization is postponed until shortly before we fill inode contents.
> + * before filling inode data) immediately.
> + */
> unlock_buffer(bh);
> goto has_buffer;
> }
> @@ -5026,6 +5028,24 @@ static int ext4_do_update_inode(handle_t *handle,
> gid_t i_gid;
> projid_t i_projid;
>
> + /*
> + * If the buffer is not uptodate, it means all information of inode
^^^^^^^^
of the inode is
> + * in memory and we got this buffer without reading the block. We
> + * must be cautious that once we mark the buffer as uptodate, we
> + * rely on filling in the correct inode data later in this function.
> + * Otherwise if we getting the left falsepositive buffer when
I'd rephrase this sentence as: Otherwise if we left uptodate buffer without
copying proper inode contents, we could corrupt the inode on disk after
allocating another inode in the same block.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
