On Fri, 2009-12-11 at 16:06 +0200, Surbhi Palande wrote:
> This patch fixes the upstream bug# 14286. When the address of an extent
> corresponding to a given block is NULL and the tree is being traversed for
> fetching such an address, a -EIO should be reported instead of a BUG(). This
> situation should normally not occur. However if it does, then the system
> should be rendered usable.
>
> Signed-off-by: Surbhi Palande <surbhi.palande@xxxxxxxxxxxxx>
> ---
> fs/ext4/extents.c | 7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 3a7928f..51f87f3 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3190,7 +3190,12 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
> * this situation is possible, though, _during_ tree modification;
> * this is why assert can't be put in ext4_ext_find_extent()
> */
> - BUG_ON(path[depth].p_ext == NULL && depth != 0);
> + if (path[depth].p_ext == NULL && depth != 0) {
> + err = -EIO;
> + printk(KERN_ERR "\n ext4 fs error in %s,%s,%s while reading a block ", \
> + __FILE__, __func__, __LINE__);
> + goto out2;
> + }
> eh = path[depth].p_hdr;
>
> ex = path[depth].p_ext;
As it happens, I fixed this locally but, as I considered it a band-aid
fix at the time, I never pushed it to you guys. My version of the fix
is below; it dumps more information before returning the EIO. I don't
have a strong preference between the two versions but I would like to
see the commentary included and the extra information is often useful
during debugging.
Signed-off-by: Frank Mayhar <fmayhar@xxxxxxxxxx>
fs/ext4/extents.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f7bdd55..7aa0bf6 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2859,8 +2859,24 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
* consistent leaf must not be empty;
* this situation is possible, though, _during_ tree modification;
* this is why assert can't be put in ext4_ext_find_extent()
+ *
+ * We don't want to panic in this case, as it can lead to a crash
+ * loop; instead we want to catch the error and abort.
*/
- BUG_ON(path[depth].p_ext == NULL && depth != 0);
+ if (path[depth].p_ext == NULL && depth != 0) {
+ printk(KERN_ERR
+ "EXT4-fs (%s): corrupt extent node ino %lu iblock %d"
+ " depth %d pblock %lld\n",
+ inode->i_sb->s_id, inode->i_ino, iblock, depth,
+ path[depth].p_block);
+ if (!path[depth].p_hdr)
+ path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
+ printk(KERN_ERR "EXT4-fs (%s): eh_entries %d eh_max %d\n",
+ inode->i_sb->s_id, path[depth].p_hdr->eh_entries,
+ path[depth].p_hdr->eh_max);
+ err = -EIO;
+ goto out2;
+ }
eh = path[depth].p_hdr;
ex = path[depth].p_ext;
--
Frank Mayhar <fmayhar@xxxxxxxxxx>
Google, Inc.
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