The patch titled
Subject: mm: remove nrexceptional from inode: remove BUG_ON
has been added to the -mm tree. Its filename is
mm-remove-nrexceptional-from-inode-remove-bug_on.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-remove-nrexceptional-from-inode-remove-bug_on.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-remove-nrexceptional-from-inode-remove-bug_on.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: remove nrexceptional from inode: remove BUG_ON
clear_inode()'s BUG_ON(!mapping_empty(&inode->i_data)) is unsafe: we know
of two ways in which nodes can and do (on rare occasions) get left behind.
Until those are fixed, do not BUG_ON() nor even WARN_ON(). Yes, this
will then leak those nodes (or the next user of the struct inode may use
them); but this has been happening for years, and the new
BUG_ON(!mapping_empty) was only guilty of revealing that. A proper fix
will follow, but no hurry.
Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2104292229380.16080@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/inode.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/inode.c~mm-remove-nrexceptional-from-inode-remove-bug_on
+++ a/fs/inode.c
@@ -529,7 +529,14 @@ void clear_inode(struct inode *inode)
*/
xa_lock_irq(&inode->i_data.i_pages);
BUG_ON(inode->i_data.nrpages);
- BUG_ON(!mapping_empty(&inode->i_data));
+ /*
+ * Almost always, mapping_empty(&inode->i_data) here; but there are
+ * two known and long-standing ways in which nodes may get left behind
+ * (when deep radix-tree node allocation failed partway; or when THP
+ * collapse_file() failed). Until those two known cases are cleaned up,
+ * or a cleanup function is called here, do not BUG_ON(!mapping_empty),
+ * nor even WARN_ON(!mapping_empty).
+ */
xa_unlock_irq(&inode->i_data.i_pages);
BUG_ON(!list_empty(&inode->i_data.private_list));
BUG_ON(!(inode->i_state & I_FREEING));
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-remove-nrexceptional-from-inode-remove-bug_on.patch
mm-restore-node-stat-checking-in-proc-sys-vm-stat_refresh.patch
mm-no-more-einval-from-proc-sys-vm-stat_refresh.patch
mm-proc-sys-vm-stat_refresh-skip-checking-known-negative-stats.patch
mm-proc-sys-vm-stat_refresh-stop-checking-monotonic-numa-stats.patch
