The patch titled
Subject: tmpfs: fix link accounting when a tmpfile is linked in
has been added to the -mm tree. Its filename is
tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-in.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-in.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-in.patch
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From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Subject: 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@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>
---
--- a/mm/shmem.c~tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-in
+++ a/mm/shmem.c
@@ -2854,10 +2854,14 @@ static int shmem_link(struct dentry *old
* 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);
_
Patches currently in -mm which might be from darrick.wong@xxxxxxxxxx are
tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-in.patch
