AUTOSEL is wrong to select this commit without also selecting
29b00e609960 ("tmpfs: fix uninitialized return value in shmem_link")
which contains the tag
Fixes: 1062af920c07 ("tmpfs: fix link accounting when a tmpfile is linked in")
Please add 29b00e609960 for those 6 trees, or else omit 1062af920c07 for now.
Thanks,
Hugh
On Wed, 13 Mar 2019, Sasha Levin wrote:
> From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
>
> [ Upstream commit 1062af920c07f5b54cf5060fde3339da6df0cf6b ]
>
> tmpfs has a peculiarity of accounting hard links as if they were
> separate inodes: so that when the number of inodes is limited, as it is
> by default, a user cannot soak up an unlimited amount of unreclaimable
> dcache memory just by repeatedly linking a file.
>
> But when v3.11 added O_TMPFILE, and the ability to use linkat() on the
> fd, we missed accommodating this new case in tmpfs: "df -i" shows that
> an extra "inode" remains accounted after the file is unlinked and the fd
> closed and the actual inode evicted. If a user repeatedly links
> tmpfiles into a tmpfs, the limit will be hit (ENOSPC) even after they
> are deleted.
>
> Just skip the extra reservation from shmem_link() in this case: there's
> a sense in which this first link of a tmpfile is then cheaper than a
> hard link of another file, but the accounting works out, and there's
> still good limiting, so no need to do anything more complicated.
>
> Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1902182134370.7035@eggly.anvils
> Fixes: f4e0c30c191 ("allow the temp files created by open() to be linked to")
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Reported-by: Matej Kupljen <matej.kupljen@xxxxxxxxx>
> Acked-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
> mm/shmem.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 5d07e0b1352f..7872e3b75e57 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2852,10 +2852,14 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentr
> * No ordinary (disk based) filesystem counts links as inodes;
> * but each new link needs a new dentry, pinning lowmem, and
> * tmpfs dentries cannot be pruned until they are unlinked.
> + * But if an O_TMPFILE file is linked into the tmpfs, the
> + * first link must skip that, to get the accounting right.
> */
> - ret = shmem_reserve_inode(inode->i_sb);
> - if (ret)
> - goto out;
> + if (inode->i_nlink) {
> + ret = shmem_reserve_inode(inode->i_sb);
> + if (ret)
> + goto out;
> + }
>
> dir->i_size += BOGO_DIRENT_SIZE;
> inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
> --
> 2.19.1
