From: Hugh Dickins Date: Sun, 10 Jul 2016 23:46:32 +0000 (-0700) Subject: tmpfs: fix regression hang in fallocate undo X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=7f556567036cb7f89aabe2f0954b08566b4efb53;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git tmpfs: fix regression hang in fallocate undo 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") Cc: stable@vger.kernel.org Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds --- diff --git a/mm/shmem.c b/mm/shmem.c index 24463b67b6ef..171dee7a131f 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2225,9 +2225,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, error = shmem_getpage(inode, index, &page, SGP_FALLOC); if (error) { /* Remove the !PageUptodate pages we added */ - shmem_undo_range(inode, - (loff_t)start << PAGE_SHIFT, - ((loff_t)index << PAGE_SHIFT) - 1, true); + if (index > start) { + shmem_undo_range(inode, + (loff_t)start << PAGE_SHIFT, + ((loff_t)index << PAGE_SHIFT) - 1, true); + } goto undone; }