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authorTakashi Iwai <tiwai@suse.de>2019-06-19 15:18:26 +0200
committerTakashi Iwai <tiwai@suse.de>2019-06-19 15:18:28 +0200
commit6d094336cd515b3c66bde44d0b1e2f594baee0dc (patch)
parenta31492b4a778cfdd60caadb96cede67904fb2e21 (diff)
tmpfs: fix link accounting when a tmpfile is linked in
2 files changed, 65 insertions, 0 deletions
diff --git a/patches.fixes/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-i.patch b/patches.fixes/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-i.patch
new file mode 100644
index 0000000000..13f7743b9a
--- /dev/null
+++ b/patches.fixes/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-i.patch
@@ -0,0 +1,64 @@
+From 1062af920c07f5b54cf5060fde3339da6df0cf6b Mon Sep 17 00:00:00 2001
+From: "Darrick J. Wong" <darrick.wong@oracle.com>
+Date: Thu, 21 Feb 2019 08:48:09 -0800
+Subject: [PATCH] tmpfs: fix link accounting when a tmpfile is linked in
+Git-commit: 1062af920c07f5b54cf5060fde3339da6df0cf6b
+Patch-mainline: v5.0-rc8
+References: bsc#1051510
+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>
+Acked-by: Takashi Iwai <tiwai@suse.de>
+ mm/shmem.c | 10 +++++++---
+ 1 file 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);
diff --git a/series.conf b/series.conf
index f79066ead7..021367fa13 100644
--- a/series.conf
+++ b/series.conf
@@ -21349,6 +21349,7 @@
+ patches.fixes/tmpfs-fix-link-accounting-when-a-tmpfile-is-linked-i.patch