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Date:   Fri, 1 Feb 2019 18:32:04 +0000
From:   "Burton, Ross" <ross.burton@...el.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] create_inode: fix copying large files

Yeah, you're right, thanks for the review.

Ross

On Fri, 1 Feb 2019 at 17:47, Darrick J. Wong <darrick.wong@...cle.com> wrote:
>
> On Fri, Feb 01, 2019 at 12:51:59PM +0000, Ross Burton wrote:
> > When copying large files into a ext filesystem at mkfs time the copy fails at
> > 2^31 bytes in.  There are two problems:
> >
> > copy_file_chunk() passes an offset (off_t, 64-bit typically) to
> > ext2fs_file_lseek() which expects a ext2_off_t (typedef to __u32) so the value
> > is truncated. Solve by calling ext2fs_file_llseek() which takes a u64 offset
> > instead.
> >
> > try_lseek_copy() rounds the data and hole offsets as found by lseek() to block
> > boundaries, but the calculation gets truncated to 32-bits.  Solve by casting the
> > 32-bit blocksize to off_t to ensure this doesn't happen.
> >
> > Signed-off-by: Ross Burton <ross.burton@...el.com>
> > ---
> >  misc/create_inode.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/misc/create_inode.c b/misc/create_inode.c
> > index 05aa6363..f106dcda 100644
> > --- a/misc/create_inode.c
> > +++ b/misc/create_inode.c
> > @@ -438,7 +438,7 @@ static errcode_t copy_file_chunk(ext2_filsys fs, int fd, ext2_file_t e2_file,
> >                               ptr += blen;
> >                               continue;
> >                       }
> > -                     err = ext2fs_file_lseek(e2_file, off + bpos,
> > +                     err = ext2fs_file_llseek(e2_file, off + bpos,
> >                                               EXT2_SEEK_SET, NULL);
> >                       if (err)
> >                               goto fail;
> > @@ -481,7 +481,7 @@ static errcode_t try_lseek_copy(ext2_filsys fs, int fd, struct stat *statbuf,
> >                       return EXT2_ET_UNIMPLEMENTED;
> >
> >               data_blk = data & ~(fs->blocksize - 1);
>
> Do we need to cast this one too?  ^^^^^^^
>
> (Looks reasonable otherwise...)
>
> --D
>
> > -             hole_blk = (hole + (fs->blocksize - 1)) & ~(fs->blocksize - 1);
> > +             hole_blk = (hole + (off_t)(fs->blocksize - 1)) & ~(off_t)(fs->blocksize - 1);
> >               err = copy_file_chunk(fs, fd, e2_file, data_blk, hole_blk, buf,
> >                                     zerobuf);
> >               if (err)
> > --
> > 2.11.0
> >

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