On Sat 17-11-18 18:35:23, Theodore Ts'o wrote:
> Today, when sb_bread() returns NULL, this can either be because of an
> I/O error or because the system failed to allocate the buffer. Since
> it's an old interface, changing would require changing many call
> sites.
>
> So instead we create our own ext4_sb_bread(), which also allows us to
> set the REQ_META flag.
>
> Also fixed a problem in the xattr code where a NULL return in a
> function could also mean that the xattr was not found, which could
> lead to the wrong error getting returned to userspace.
>
> Fixes: ac27a0ec112a ("ext4: initial copy of files from ext3")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
...
> +/*
> + * This works like sb_bread() except it uses ERR_PTR for error
> + * returns. Currently with sb_bread it's impossible to distinguish
> + * between ENOMEM and EIO situations (since both result in a NULL
> + * return.
> + */
> +struct buffer_head *
> +ext4_sb_bread(struct super_block *sb, sector_t block)
> +{
> + struct buffer_head *bh = sb_getblk(sb, block);
> +
> + if (bh == NULL)
> + return ERR_PTR(-ENOMEM);
> + if (buffer_uptodate(bh))
> + return bh;
> + ll_rw_block(REQ_OP_READ, REQ_META | REQ_PRIO, 1, &bh);
Is there a reason for REQ_PRIO? I'm not sure all REQ_META reads are really
a priority ones...
> + wait_on_buffer(bh);
> + if (buffer_uptodate(bh))
> + return bh;
> + put_bh(bh);
> + return ERR_PTR(-EIO);
> +}
> +
> static int ext4_verify_csum_type(struct super_block *sb,
> struct ext4_super_block *es)
> {
...
> @@ -696,26 +695,23 @@ ext4_xattr_block_list(struct dentry *dentry, char *buffer, size_t buffer_size)
> ea_idebug(inode, "buffer=%p, buffer_size=%ld",
> buffer, (long)buffer_size);
>
> - error = 0;
> if (!EXT4_I(inode)->i_file_acl)
> - goto cleanup;
> + return NULL;
NULL looks wrong here - should be 0 I guess...
Otherwise the patch looks good to me.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
