From: Vladimir Davydov <vdavy...@parallels.com> Author: Maxim Patlasov Email: mpatla...@parallels.com Subject: fs: allow to remove swapfile hardlinks Date: Tue, 11 Mar 2014 20:33:12 +0400
There is nothing wrong to allow unlink(2) on a swapfile unless this is the last link (i_nlink == 1). The patch is useful for sharing a ploop image (which uses the same S_SWAPFILE flag for protection against truncate as swapfiles) among several containers by hardlinks. Otherwise, CT destroy would fail due to inability to unlink image file. >>>> Nice. >>>> Why it's not done in upstream? >>>> I mean, is there any reason against it? >>> >>> No, I think. They had solved the problem of lost swapfile by the >>> simplest patch: disable any unlink. >>> >> >> Are you going to suggest to patch to the upstream? >> Or it's just our local usage scenario? > > It's our own invention -- to use S_SWAPFILE for protection ploop images > from truncation. Ordinary loop block-device doesn't use it. Nobody else > (except swapfiles) uses it. So its our local usage from which nobody > else can get a benefit (until we didn't push ploop upstream in some form). https://jira.sw.ru/browse/PSBM-25310 Signed-off-by: Maxim Patlasov <mpatla...@parallels.com> ============================================================================= Related to https://jira.sw.ru/browse/PSBM-33650 Signed-off-by: Vladimir Davydov <vdavy...@parallels.com> ============================================================================= VZ 8 rebase part https://jira.sw.ru/browse/PSBM-127782 vz7 commit: ede015466b21 ("ve/fs: Port diff-ve-fs-allow-to-remove-swapfile-hardlinks") Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalit...@virtuozzo.com> khorenko@: currently we don't use S_SWAPFILE flag as a protection for ploops, but it might be useful for fast path later, so let's apply the patch for now, it's simple. (cherry picked from vz8 commit f759285a1949df2e9c8e65b5916079f546843d25) Signed-off-by: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com> --- fs/namei.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index 47c0fe3..38f52c1 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2809,7 +2809,8 @@ static int may_delete(struct user_namespace *mnt_userns, struct inode *dir, if (check_sticky(mnt_userns, dir, inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || - HAS_UNMAPPED_ID(mnt_userns, inode)) + HAS_UNMAPPED_ID(mnt_userns, inode) || + (IS_SWAPFILE(inode) && inode->i_nlink == 1)) return -EPERM; if (isdir) { if (!d_is_dir(victim)) -- 1.8.3.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
