[tip:locking/core] locking/rwsem, fs: Use killable down_read() in iterate_dir()

[tip-bot for Kirill Tkhai]

Commit-ID:  0dc208b5d5feedc795cbf124539decd182c8e99e
Gitweb:     https://git.kernel.org/tip/0dc208b5d5feedc795cbf124539decd182c8e99e
Author:     Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
AuthorDate: Fri, 29 Sep 2017 19:06:48 +0300
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 10 Oct 2017 11:50:16 +0200

locking/rwsem, fs: Use killable down_read() in iterate_dir()

There was mutex_lock_interruptible() initially, and it was changed
to rwsem, but there were not killable rwsem primitives that time.
>From commit 9902af79c01a:

    "The main issue is the lack of down_write_killable(), so the places
     like readdir.c switched to plain inode_lock(); once killable
     variants of rwsem primitives appear, that'll be dealt with"

Use down_read_killable() same as down_write_killable() in !shared
case, as concurrent inode_lock() may take much time, that may be
wanted to be interrupted by user.

Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: arnd@xxxxxxxx
Cc: avagin@xxxxxxxxxxxxx
Cc: davem@xxxxxxxxxxxxx
Cc: fenghua.yu@xxxxxxxxx
Cc: gorcunov@xxxxxxxxxxxxx
Cc: heiko.carstens@xxxxxxxxxx
Cc: hpa@xxxxxxxxx
Cc: ink@xxxxxxxxxxxxxxxxxxxx
Cc: mattst88@xxxxxxxxx
Cc: rientjes@xxxxxxxxxx
Cc: rth@xxxxxxxxxxx
Cc: schwidefsky@xxxxxxxxxx
Cc: tony.luck@xxxxxxxxx
Cc: viro@xxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/150670120820.23930.5455667921545937220.stgit@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 fs/readdir.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/readdir.c b/fs/readdir.c
index 8965954..7c584bb 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -36,13 +36,12 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 	if (res)
 		goto out;
 
-	if (shared) {
-		inode_lock_shared(inode);
-	} else {
+	if (shared)
+		res = down_read_killable(&inode->i_rwsem);
+	else
 		res = down_write_killable(&inode->i_rwsem);
-		if (res)
-			goto out;
-	}
+	if (res)
+		goto out;
 
 	res = -ENOENT;
 	if (!IS_DEADDIR(inode)) {