diff options
| author | Darrick J. Wong <darrick.wong@oracle.com> | 2019-02-21 08:48:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-21 09:01:00 -0800 |
| commit | 1062af920c07f5b54cf5060fde3339da6df0cf6b (patch) | |
| tree | 42c3494136a9d8338ddfdbeef4db7a726d757b0d /mm | |
| parent | 4e37504d1c49eec6434d0cc97278d2b51c9e8763 (diff) | |
tmpfs: fix link accounting when a tmpfile is linked in
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@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Matej Kupljen <matej.kupljen@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/shmem.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 6ece1e2fe76e..0905215fb016 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2854,10 +2854,14 @@ 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); |