On Wed, Dec 09, 2009 at 03:57:13PM +0100, Jan Kara wrote:
> On Tue 08-12-09 09:42:09, Nick Piggin wrote:
> > I also have commented a possible bug in existing ext2 code, marked with XXX.
> >
> > Cc: linux-ext4@xxxxxxxxxxxxxxx
> > Cc: Christoph Hellwig <hch@xxxxxx>
> > Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
> ...
> > @@ -752,8 +764,8 @@ int __ext2_write_begin(struct file *file
> > loff_t pos, unsigned len, unsigned flags,
> > struct page **pagep, void **fsdata)
> > {
> > - return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
> > - ext2_get_block);
> > + return block_write_begin_newtrunc(file, mapping, pos, len, flags,
> > + pagep, fsdata, ext2_get_block);
> > }
> OK, but you should update the code in dir.c using __ext2_write_begin,
> shouldn't you?
To trim off blocks past i_size on failure? Yes I guess it should.
In fact, the ext2_write_failed call could just go into here I think.
I'll take a look.
> > +static int ext2_write_end(struct file *file, struct address_space *mapping,
> > + loff_t pos, unsigned len, unsigned copied,
> > + struct page *page, void *fsdata)
> > +{
> > + int ret;
> > +
> > + ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
> > + if (ret < len)
> > + ext2_write_failed(mapping, pos + len);
> > + return ret;
> > }
> OK, when doing this, please also update ext2_commit_chunk in dir.c...
I think commit_chunk is OK. Because block_write_end does not fail
and the only reason for checking failure here is in case of a short
copy (which won't happen in dir.c code).
> > +static void ext2_truncate_blocks(struct inode *inode, loff_t offset)
> > +{
> > + /*
> > + * XXX: it seems like a bug here that we don't allow
> > + * IS_APPEND inode to have blocks-past-i_size trimmed off.
> > + * review and fix this.
> > + *
> > + * Also would be nice to be able to handle IO errors and such,
> > + * but that's probably too much to ask.
> > + */
> > + if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
> > + S_ISLNK(inode->i_mode)))
> > + return;
> > + if (ext2_inode_is_fast_symlink(inode))
> > + return;
> > + if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
> > + return;
> Yes, I'd remove IS_APPEND check from here.
Didn't want to change that in this patch, but I'm happy for someone to
fix it (and in ext3/4 etc).
The checks probably should be done at a different level anyway: by the
time that this code gets called, the pagecache is truncated and i_size
modified anyway so it seems buggy if this made any difference.
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