Jan Kara wrote: > On Thu 30-07-09 13:39:12, Eric Sandeen wrote: ... Honza >> This is all about right, but it's tricky, because right now, get_block >> is called in the direct IO path from get_more_blocks(), and it's called >> with create == 0 unless OWN_LOCKING is specified. If we do get_block w/ >> create == 0 and find prealloc'd blocks, then we're given back unmapped >> buffer heads. This looks like a hole, and so DIO falls back to buffered. >> >> Right now the only way to get create == 1 sent to get_blocks via >> directio is to do OWN_LOCKING, which implies... we have to do our own >> locking, and it'll take some time to get it right I think. > But the get_block function called by get_more_blocks() is specified in > ext4_direct_IO. So we can provide it with a special direct_IO version of > get_block function which happily maps also uninitialized extents... It's a > slight hack, but maintainable IMHO. Hm, perhaps. xfs does have a xfs_get_blocks_direct() that it uses for DIO. Although returning mapped unwritten blocks ... well, we'll have to be sure it doesn't cause any problems elsewhere. :) -Eric > Honza -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
