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    SubjectRe: [V3 PATCH 1/2] tmpfs: add fallocate support
    On Thu, 24 Nov 2011 11:22:34 +0800
    Cong Wang <amwang@redhat.com> wrote:

    > 于 2011年11月24日 11:01, KAMEZAWA Hiroyuki 写道:
    > > On Wed, 23 Nov 2011 21:46:39 -0500
    > > KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com> wrote:
    > >
    > >>>> + while (index< end) {
    > >>>> + ret = shmem_getpage(inode, index,&page, SGP_WRITE, NULL);
    > >>>
    > >>> If the 'page' for index exists before this call, this will return the page without
    > >>> allocaton.
    > >>>
    > >>> Then, the page may not be zero-cleared. I think the page should be zero-cleared.
    > >>
    > >> No. fallocate shouldn't destroy existing data. It only ensure
    > >> subsequent file access don't make ENOSPC error.
    > >>
    > > FALLOC_FL_KEEP_SIZE
    > > This flag allocates and initializes to zero the disk space
    > > within the range specified by offset and len. ....
    > >
    > > just manual is unclear ? it seems that the range [offset, offset+len) is
    > > zero cleared after the call.
    >
    > I think we should fix the man page, because at least ext4 doesn't clear
    > the original contents,
    >
    > % echo hi > /tmp/foobar
    > % fallocate -n -l 1 -o 10 /tmp/foobar
    > % hexdump -Cv /tmp/foobar
    > 00000000 68 69 0a |hi.|
    > 00000003
    >

    thank you for checking. So, at failure path, original data should not be
    cleared, either.

    Thanks,
    -Kame



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