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SubjectRe: ext4: cache all of an extent tree's leaf block upon reading
On Thu, Sep 05, 2013 at 01:38:48AM +0000, Linux Kernel wrote:
> Gitweb: http://git.kernel.org/linus/;a=commit;h=107a7bd31ac003e42c0f966aa8e5b26947de6024
> Commit: 107a7bd31ac003e42c0f966aa8e5b26947de6024
> Parent: 3be78c73179c9347bdc0a92b2898063bd2300ff7
> Author: Theodore Ts'o <tytso@mit.edu>
> AuthorDate: Fri Aug 16 21:23:41 2013 -0400
> Committer: Theodore Ts'o <tytso@mit.edu>
> CommitDate: Fri Aug 16 21:23:41 2013 -0400
>
> ext4: cache all of an extent tree's leaf block upon reading


> + * ext4_es_cache_extent() inserts information into the extent status
> + * tree if and only if there isn't information about the range in
> + * question already.
> + */
> +void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
> + ext4_lblk_t len, ext4_fsblk_t pblk,
> + unsigned int status)
> +{
> + struct extent_status *es;
> + struct extent_status newes;
> + ext4_lblk_t end = lblk + len - 1;
> +
> + newes.es_lblk = lblk;
> + newes.es_len = len;
> + ext4_es_store_pblock(&newes, pblk);


ext4_es_store_pblock or's the pblk with the existing contents of the struct member.
(albeit masked with ES_MASK)

Should there be a

newes.es_pblk = 0;

up there too ?

It seems like if the stack happened to contain any of ES_WRITTEN | ES_UNWRITTEN | ES_DELAYED | ES_HOLE
then it could leak through into the new extent status.

Dave



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