2014-02-03 0:21 GMT+09:00, Matthew Wilcox <matthew@xxxxxx>: > On Sun, Feb 02, 2014 at 08:16:24AM -0700, Matthew Wilcox wrote: >> On Sun, Feb 02, 2014 at 02:41:34PM +0900, Namjae Jeon wrote: >> > The semantics of this flag are following: >> > 1) It collapses the range lying between offset and length by removing >> > any data >> > blocks which are present in this range and than updates all the >> > logical >> > offsets of extents beyond "offset + len" to nullify the hole created >> > by >> > removing blocks. In short, it does not leave a hole. >> > 2) It should be used exclusively. No other fallocate flag in >> > combination. >> > 3) Offset and length supplied to fallocate should be fs block size >> > aligned >> > in case of xfs and ext4. >> > 4) Collaspe range does not work beyond i_size. >> >> What if the file is mmaped at the time somebody issues this command? >> Seems to me we should drop pagecache pages that overlap with the >> removed blocks. If the removed range is not a multiple of PAGE_SIZE, >> then we should also drop any pagecache pages after the removed range. Hi Matthew. Yes, right. So both xfs and ext4 call truncate_pagecache_range to drop page caches before removing blocks. truncate_pagecache_range(inode, offset, -1); and end offset is -1, which mean all page cache will be dropped from start offset to the end of file. > > Oops, forgot to add "and if it is a multiple of page size, then we need > to update the offsets of any pages after the removed page". We should > probably start easy though; just drop all pages that overlap the beginning > of the affected range to the end of the file. Yes, right. current implementation does exactly as you pointed > At some later point, > if there's demand, we can add the optimisation to adjust the offsets of > pages still in the cache. -> Yes, Right. But if we consider that fs block size can be less than page cache size,(512B, 1K, 2K) I thought that it is proper to drop all pages from the start offset to the end of the file. Thanks for your reply. > > -- > Matthew Wilcox Intel Open Source Technology Centre > "Bill, look, we understand that you're interested in selling us this > operating system, but compare it to ours. We can't possibly take such > a retrograde step." > _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
