From: Namjae Jeon Subject: Re: Punching hole using fallocate is not removing the uninit extent from extent tree Date: Mon, 18 Jun 2012 20:45:17 +0900 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ashish Sangwan , linux-ext4@vger.kernel.org, Amit Sahrawat , "linux-kernel@vger.kernel.org" To: =?UTF-8?B?THVrw6HFoSBDemVybmVy?= Return-path: Received: from mail-wg0-f44.google.com ([74.125.82.44]:63878 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751052Ab2FRLpT convert rfc822-to-8bit (ORCPT ); Mon, 18 Jun 2012 07:45:19 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: Add in mail loop. 2012/6/18, Namjae Jeon : > 2012/6/18, Luk=C3=A1=C5=A1 Czerner : >> On Mon, 28 May 2012, Ashish Sangwan wrote: >> >>> Date: Mon, 28 May 2012 19:38:05 +0530 >>> From: Ashish Sangwan >>> To: linux-ext4@vger.kernel.org >>> Subject: Punching hole using fallocate is not removing the uninit e= xtent >>> from >>> extent tree >> >> Hi Ashish, >> >> I am looking at you patch, however I am not able to reproduce this. >> Can you please send more information (script preferably) on how to >> reproduce this problem ? >> > Hi. Lukas. > If you use the below script, you can easily reproduce this problem. > And I can not attach script file, so I write script code in this mail= =2E > you can paste it to file. > > fragmentation.sh > ---------------------------------------------------------------------= -- > dd if=3D/dev/zero of=3D12kb bs=3D4096 count=3D6 > index=3D0 > while [ $? =3D=3D 0 ] > do > index=3D$(($index + 1)) > cp 12kb $1/file1.$index > done > echo "Partition filled" > sync > df -h > index=3D0 > while [ $? =3D=3D 0 ] > do > index=3D$(($index + 2)) > sync > rm $1/file1.$index > done > sync > echo "fragmented partition $1 with 4KB files" > ---------------------------------------------------------------------= ---- > > 1. create smaill partition(500MB) to reproduce rapidly. > 2. plz run this script to make fragmentation partition after making > dummy directory like this. > mkdir test_dir > ./fragmentation.sh test_dir > > 3. dd if=3D/dev/zero of=3Dd_file bs=3D1024 count=3D10240 > 4. you can see file depth is not zero.(dump_extents d_file > 5. and try to fallocate offset : 4096 lengh 4096. > >> Also what kernel version did try this on ? > We are using 3.0.20 kernel patched your punch hole patches. > > Please let us know in case of any queries. > > Thanks. > >> >> Thanks! >> -Lukas >> >>> >>> I have created a formatted EXT4 partition such that every single >>> extent is exactly 6blocks (24KB) of length. >>> I used hole punch on 2 different files. >>> >>> CASE 1: In first situation, file size is 72KB. There are total 3 >>> extents each 24KB length. Using fallocate to punch hole starting at >>> offset 4096 and length 4096, >>> dump_extents gives the following expected output : >>> >>> Before punching hole : >>> Level Entries Logical Physical Length Flags >>> 0/ 0 1/ 2 0 - 5 1856 - 1861 6 >>> 0/ 0 2/ 2 6 - 11 1868 - 1873 6 >>> >>> After punching hole : >>> Level Entries Logical Physical Length Flags >>> 0/ 0 1/ 3 0 - 0 1856 - 1856 1 >>> 0/ 0 2/ 3 2 - 5 1858 - 1861 4 >>> 0/ 0 3/ 3 6 - 11 1868 - 1873 6 >>> >>> The 1st extent: 0-5, is splitted into 3 extents, "0-0", "1-1", "2-5= " >>> Extent 1-1 is first marked as uninitialized in function >>> ext4_ext_map_blocks() and later removed from the extent tree by >>> ext4_ext_remove_space(). >>> >>> CASE 2: File size is 9.4MB. There are total 400 extents each 24KB >>> length, depth of extent tree at root header is 1 and there are 2 in= dex >>> entries. >>> >>> dump_extents output before punching hole: >>> Level Entries Logical Physical Length Flags >>> 0/ 1 1/ 2 0 - 2039 1922 2040 >>> 1/ 1 1/340 0 - 5 1856 - 1861 6 >>> 1/ 1 2/340 6 - 11 1868 - 1873 6 >>> < Continued likewise till 340/340 > >>> 1/ 1 340/340 2034 - 2039 5942 - 5947 6 >>> 0/ 1 2/ 2 2040 - 2399 1923 360 >>> 1/ 1 1/ 60 2040 - 2045 5954 - 5959 6 >>> 1/ 1 2/ 60 2046 - 2051 5966 - 5971 6 >>> < Continued likewise till 60/60 > >>> 1/ 1 60/ 60 2394 - 2399 6662 - 6667 6 >>> >>> dump_extents output after punching hole : >>> 0/ 1 1/ 3 0 - 5 1922 6 >>> 1/ 1 1/ 3 0 - 0 1856 - 1856 1 >>> 1/ 1 2/ 3 1 - 1 1857 - 1857 1 Uninit >>> 1/ 1 3/ 3 2 - 5 1858 - 1861 4 >>> 0/ 1 2/ 3 6 - 2039 6674 2034 >>> 1/ 1 1/339 6 - 11 1868 - 1873 6 >>> 1/ 1 2/339 12 - 17 1880 - 1885 6 >>> < Continued like wise...> >>> >>> Comparing CASE2 with CASE1, still uninit extent "1-1" is present >>> within the extent tree. >>> >>> In function ext4_ext_remove_space(), there is call to function >>> ext4_ext_rm_leaf which is responsible for removal of this extent. >>> But this function is not getting called in CASE 2 : >>> if (i =3D=3D depth) { >>> /* this is leaf block */ >>> err =3D ext4_ext_rm_leaf(handle, inode, path= , >>> start, end); >>> /* root level has p_bh =3D=3D NULL, brelse() eats this */ >>> brelse(path[i].p_bh); >>> path[i].p_bh =3D NULL; >>> i--; >>> continue; >>> } >>> >>> Varibale "i" does not become equals to "depth" because >>> ext4_ext_more_to_rm is returning "0" hence the following if conditi= on >>> is turning out to be false for 1st extent index: >>> if (ext4_ext_more_to_rm(path + i)) { >>> >>> Looking at the defination of ext4_ext_more_to_rm : >>> /* >>> * ext4_ext_more_to_rm: >>> * returns 1 if current index has to be freed (even partial) >>> */ >>> static int >>> ext4_ext_more_to_rm(struct ext4_ext_path *path) >>> { >>> BUG_ON(path->p_idx =3D=3D NULL); >>> if (path->p_idx < EXT_FIRST_INDEX(path->p_hdr)) >>> return 0; >>> >>> /* >>> * if truncate on deeper level happened, it wasn't partial, >>> * so we have to consider current index for truncation >>> */ >>> if (le16_to_cpu(path->p_hdr->eh_entries) =3D=3D path->p_bloc= k) <=3D >>> This condition is turning out to be true >>> return 0; <=3D The function is returning zero = from >>> here. >>> return 1; >>> } >>> >>> I could not understand the significance of the above mentioned if >>> condition check, if anyone could explain a little, it will be help. >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-ext= 4" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html