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Subject[tip:locking/core] locking/rwsem, fs: Use killable down_read() in iterate_dir()
Commit-ID:  0dc208b5d5feedc795cbf124539decd182c8e99e
Gitweb: https://git.kernel.org/tip/0dc208b5d5feedc795cbf124539decd182c8e99e
Author: Kirill Tkhai <ktkhai@virtuozzo.com>
AuthorDate: Fri, 29 Sep 2017 19:06:48 +0300
Committer: Ingo Molnar <mingo@kernel.org>
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@virtuozzo.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arnd@arndb.de
Cc: avagin@virtuozzo.com
Cc: davem@davemloft.net
Cc: fenghua.yu@intel.com
Cc: gorcunov@virtuozzo.com
Cc: heiko.carstens@de.ibm.com
Cc: hpa@zytor.com
Cc: ink@jurassic.park.msu.ru
Cc: mattst88@gmail.com
Cc: rientjes@google.com
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Cc: viro@zeniv.linux.org.uk
Link: http://lkml.kernel.org/r/150670120820.23930.5455667921545937220.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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)) {
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