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Re: Assertion failure in do_get_write_access() at fs/jbd/transaction.c:746


On Fri, 2002-12-06 at 20:41, Andrew Morton wrote:

> OK, I think I see what happened.
> In ext3_dirty_inode(), we open a transaction which reserves just
> a single disk block.  Because that is all we expect to write.
> But when you get all the way down to ext3_do_upodate_inode(),
> the corrupted inode data leads the filesytem to think that
> the file has a size larger than 2G.
> This triggers the logic in ext3_do_update_inode() which updates
> the superblock to say "this filesystem now has files which are
> larger than 2G".
> But that requires a journalled superblock write.  We didn't
> reserve a second block in the transaction for that, and blam.

> A robust fix for this is to update all callers of ext3_do_update_inode()
> to reserve an additional block for that eventuality.

Most callers already have it.  EXT3_SINGLEDATA_TRANS_BLOCKS already
includes the superblock, because data-touching operations already need
to include updates to the free-blocks counts in the sb.  

So most of the paths really should be safe: when a file initially
becomes that large, we should be accounting for an sb write already. 
But in the case where the sb state is incorrect when we get a
mark_inode_dirty(), we need to be able to correct it there, so I think
it's actually more correct simply to reserve the extra block just inside
ext3_dirty_inode()'s transaction.


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