On Thu, Feb 21, 2019 at 01:30:52PM -0800, Darrick J. Wong wrote: > > So does this need to account for the case of an overlapping cow block > > over a hole in the data fork (with cached data, if that is possible)? > > IIUC we introduce that possibility just below. > > I think it makes sense to ignore overlapping cow blocks for zeroing a > hole in the data fork -- the user told us to zero part of a file that > didn't have nonzero contents in it, so we just leave the speculative cow > allocation for that block alone. For a speculative preallocation I agree. But if we have valid data in there due to a cowextsize preallocation being used for data we should handle it properly. > > > iomap->flags |= IOMAP_F_NEW; > > > > This looks like it flags the mapping new if we reserve cow blocks, which > > I don't think is quite right. > > Hmmm. I thought it was correct -- if the write fails, we punch out the > pagecache and trim any delalloc blocks in the data fork. If they user > tries to reread the area of the failed write we'll just read them back > in from disk...? Yes, I don't think it is actively harmful, but we don't really need it either.
