On Wed, Sep 03, 2014 at 07:21:16PM +1000, Dave Chinner wrote: > > @@ -481,9 +484,14 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) > > err = dax_get_addr(&bh, &addr, inode->i_blkbits); > > if (err < 0) > > return err; > > + /* > > + * ext4 sometimes asks to zero past the end of a block. It > > + * really just wants to zero to the end of the block. > > + */ > > + length = min_t(unsigned, length, PAGE_CACHE_SIZE - offset); > > memset(addr + offset, 0, length); > > Sorry, what? > > You introduce that bug with the way dax_truncate_page() is redefined > to always pass PAGE_CACHE_SIZE a a length later on in this patch. > into the function. That's hardly an ext4 bug.... ext4 does (or did?) have this bug (expectation?). I then take advantage of the fact that we have to accommodate it, so there are now two places that have to accommodate it. I forget what the path was that has that assumption, but xfstests used to display it. I'm away this week (... bad timing), but I can certainly fix it elsewhere in ext4 next week. > > int dax_clear_blocks(struct inode *, sector_t block, long size); > > +int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t); > > int dax_truncate_page(struct inode *, loff_t from, get_block_t); > > It's still defined as a function that doesn't exist now.... Oops. > > +/* Can't be a function because PAGE_CACHE_SIZE is defined in pagemap.h */ > > +#define dax_truncate_page(inode, from, get_block) \ > > + dax_zero_page_range(inode, from, PAGE_CACHE_SIZE, get_block) > > And then redefined as a macro here. Heh, which means we never notice the stale delaration above. Thanks, C! > This is wrong, IMO, > dax_truncate_page() should remain as a function and it should > correctly calculate how much of the page shoul dbe trimmed, not > leave landmines that other code has to clean up... > > (Yup, I'm tracking down a truncate bug in XFS from fsx...) I'll put an assert in the rewrite, make sure that nobody's trying to overtruncate. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>