Hi Dave, Yes, the user space defrag works and satisfies my requirement (almost no change from your example code). Let me know if you want it in xfsprog. Thanks, Wengang > On Dec 18, 2023, at 8:27 AM, Wengang Wang <wen.gang.wang@xxxxxxxxxx> wrote: > > > >> On Dec 15, 2023, at 12:20 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: >> >> On Fri, Dec 15, 2023 at 05:07:36PM +0000, Wengang Wang wrote: >>>> On Dec 14, 2023, at 7:15 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: >>>> If we were to implement this as, say, and xfs_spaceman operation >>>> then all the user controlled policy bits (like inter chunk delays, >>>> chunk sizes, etc) then just becomes command line parameters for the >>>> defrag command... >>> >>> >>> Ha, the idea from user space is very interesting! >>> So far I have the following thoughts: >>> 1). If the FICLONERANGE/FALLOC_FL_UNSHARE_RANGE/FALLOC_FL_PUNCH works on a FS without reflink >>> enabled. >> >> Personally, I don't care if reflink is not enabled. It's the default >> for new filesystems, and it's cost free for anyone who is not >> using reflink so there is no reason for anyone to turn it off. >> >> What I'm saying is "don't compromise the design of the functionality >> required just because someone might choose to disable that >> functionality". >> >>> 2). What if there is a big hole in the file to be defragmented? Will it cause block allocation and writing blocks with >>> zeroes. >> >> Unshare skips holes. >> >>> 3). In case a big range of the file is good (not much fragmented), the ‘defrag’ on that range is not necessary. >> >> xfs_fsr already deals with this - it uses XFS_IOC_GETBMAPX to scan >> the extent list to determine what to defrag, to replicate unwritten >> regions and to skip holes. Having to scan the extent list is kinda >> expected for a defrag utility >> >>> 4). The use space defrag can’t use a try-lock mode to make IO requests have priorities. I am not sure if this is very important. >> >> As long as the individual operations aren't holding locks for a long >> time, I doubt it matters. And you can use ionice to make sure the IO >> being issued has background priority in the block scheduler... >> > > Yes, thanks for the answers. > I will try it out. > > Thanks, > Wengang
