From: Mingming Cao Subject: Re: [PATCH] ext4: Fix data corruption when writing to prealloc area Date: Fri, 18 Jul 2008 10:02:33 -0700 Message-ID: <1216400553.6869.11.camel@mingming-laptop> References: <1216387021-26384-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: tytso@mit.edu, sandeen@redhat.com, linux-ext4@vger.kernel.org, Shehjar Tikoo To: "Aneesh Kumar K.V" Return-path: Received: from e1.ny.us.ibm.com ([32.97.182.141]:38737 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755520AbYGRRDF (ORCPT ); Fri, 18 Jul 2008 13:03:05 -0400 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e1.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m6IH341I013016 for ; Fri, 18 Jul 2008 13:03:04 -0400 Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m6IH33Tx225508 for ; Fri, 18 Jul 2008 13:03:04 -0400 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m6IH33Tw006079 for ; Fri, 18 Jul 2008 13:03:03 -0400 In-Reply-To: <1216387021-26384-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: I tried this patch, with nodelalloc, the kernel did not crash! Previous it crashes in a few minutes. but the test did not stop after fill the file by specified 2G size I noticed the write() to write to the last fallocate extent(up to 2G) returns junk value. The testcase I got from Shehjart (who originally reported the problem) is =20 http://www.gelato.unsw.edu.au/~shehjart/writefallocate.c command I use to reproduce the problem is=20 =2E/writefallocate --filesize 2147483648 --wrblksize 65536 --fallocate 1048576 --filename /mnt/ext4/a --nounlink =2E............ offset: 2147024896, written: 65536^M offset: 2147090432, written: 65536^M offset: 2147155968, written: 65536^M offset: 2147221504, written: 65536^M offset: 2147287040, written: 65536^M offset: 2147352576, written: 65536^M offset: 2147418112, written: 65535^M offset: 2147483647, written: 18446744073709551615^M fallocate offset: 2147483647^M offset: 2147483646, written: 18446744073709551615^M offset: 2147483645, written: 18446744073709551615^M offset: 2147483644, written: 18446744073709551615^M offset: 2147483643, written: 18446744073709551615^M offset: 2147483642, written: 18446744073709551615^M offset: 2147483641, written: 18446744073709551615^M offset: 2147483640, written: 18446744073709551615^M Appearently the test has fallocate/fill the 2G file, but since the last write() returns 18446744073709551615, the offset is decreased, cause th= e test continue with a break, and writes to wrong offset =E5=9C=A8 2008-07-18=E4=BA=94=E7=9A=84 18:47 +0530=EF=BC=8CAneesh Kumar= K.V=E5=86=99=E9=81=93=EF=BC=9A > We need to recalucate the path information on extent insert > even if depth doesn't change. >=20 > Signed-off-by: Aneesh Kumar K.V > --- > fs/ext4/extents.c | 41 +++++++++++++++++++++++------------------ > 1 files changed, 23 insertions(+), 18 deletions(-) >=20 > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 7bdaeec..9c8541e 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(han= dle_t *handle, > unsigned int newdepth; > /* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */ > if (allocated <=3D EXT4_EXT_ZERO_LEN) { > - /* Mark first half uninitialized. > + /* > + * iblock =3D=3D ee_block is handled by the zerouout > + * at the beginning. > + * Mark first half uninitialized. > * Mark second half initialized and zero out the > * initialized extent > */ > @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(hand= le_t *handle, > ex->ee_len =3D orig_ex.ee_len; > ext4_ext_store_pblock(ex, ext_pblock(&orig_ex)); > ext4_ext_dirty(handle, inode, path + depth); > - /* zeroed the full extent */ > + /* blocks available from iblock */ > return allocated; >=20 > } else if (err) > @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(hand= le_t *handle, > err =3D PTR_ERR(path); > return err; > } > + /* get the second half extent details */ > ex =3D path[depth].p_ext; > err =3D ext4_ext_get_access(handle, inode, > path + depth); > @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(hand= le_t *handle, > ext4_ext_store_pblock(ex, ext_pblock(&orig_ex)); > ext4_ext_dirty(handle, inode, path + depth); > /* zeroed the full extent */ > + /* blocks available from iblock */ > return allocated; >=20 > } else if (err) > @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(ha= ndle_t *handle, > */ > orig_ex.ee_len =3D cpu_to_le16(ee_len - > ext4_ext_get_actual_len(ex3)); > - if (newdepth !=3D depth) { > - depth =3D newdepth; > - ext4_ext_drop_refs(path); > - path =3D ext4_ext_find_extent(inode, iblock, path); > - if (IS_ERR(path)) { > - err =3D PTR_ERR(path); > - goto out; > - } > - eh =3D path[depth].p_hdr; > - ex =3D path[depth].p_ext; > - if (ex2 !=3D &newex) > - ex2 =3D ex; > - > - err =3D ext4_ext_get_access(handle, inode, path + depth); > - if (err) > - goto out; > + depth =3D newdepth; > + ext4_ext_drop_refs(path); > + path =3D ext4_ext_find_extent(inode, iblock, path); > + if (IS_ERR(path)) { > + err =3D PTR_ERR(path); > + goto out; > } > + eh =3D path[depth].p_hdr; > + ex =3D path[depth].p_ext; > + if (ex2 !=3D &newex) > + ex2 =3D ex; > + > + err =3D ext4_ext_get_access(handle, inode, path + depth); > + if (err) > + goto out; > + > allocated =3D max_blocks; >=20 > /* If extent has less than EXT4_EXT_ZERO_LEN and we are trying > @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(hand= le_t *handle, > ext4_ext_store_pblock(ex, ext_pblock(&orig_ex)); > ext4_ext_dirty(handle, inode, path + depth); > /* zero out the first half */ > + /* blocks available from iblock */ > return allocated; > } > } -- 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