lkml.org 
[lkml]   [2016]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.12 029/100] tmpfs: fix regression hang in fallocate undo
    Date
    From: Hugh Dickins <hughd@google.com>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit 7f556567036cb7f89aabe2f0954b08566b4efb53 upstream.

    The well-spotted fallocate undo fix is good in most cases, but not when
    fallocate failed on the very first page. index 0 then passes lend -1
    to shmem_undo_range(), and that has two bad effects: (a) that it will
    undo every fallocation throughout the file, unrestricted by the current
    range; but more importantly (b) it can cause the undo to hang, because
    lend -1 is treated as truncation, which makes it keep on retrying until
    every page has gone, but those already fully instantiated will never go
    away. Big thank you to xfstests generic/269 which demonstrates this.

    Fixes: b9b4bb26af01 ("tmpfs: don't undo fallocate past its last page")
    Signed-off-by: Hugh Dickins <hughd@google.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    mm/shmem.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    diff --git a/mm/shmem.c b/mm/shmem.c
    index ff42f161fc32..fb31c6984c09 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -1895,9 +1895,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
    NULL);
    if (error) {
    /* Remove the !PageUptodate pages we added */
    - shmem_undo_range(inode,
    - (loff_t)start << PAGE_CACHE_SHIFT,
    - ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
    + if (index > start) {
    + shmem_undo_range(inode,
    + (loff_t)start << PAGE_CACHE_SHIFT,
    + ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
    + }
    goto undone;
    }

    --
    2.9.3
    \
     
     \ /
      Last update: 2016-09-17 09:57    [W:4.067 / U:0.488 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site