linux-kernel - [PATCH] Increase limit of max_user

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Date:   Wed, 20 Jan 2021 13:02:31 +0000
From:   Eric Curtin <ericcurtin17@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     ericcurtin17@...il.com, Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        linux-doc@...r.kernel.org (open list:DOCUMENTATION),
        linux-kernel@...r.kernel.org (open list),
        linux-fsdevel@...r.kernel.org (open list:FILESYSTEMS (VFS and
        infrastructure))
Subject: [PATCH] Increase limit of max_user_watches from 1/25 to 1/16

The current default value for  max_user_watches  is the 1/16 (6.25%) of
the available low memory, divided for the "watch" cost in bytes.

Tools like inotify-tools and visual studio code, seem to hit these
limits a little to easy.

Also amending the documentation, it referred to an old value for this.

Signed-off-by: Eric Curtin <ericcurtin17@...il.com>
---
 Documentation/admin-guide/sysctl/fs.rst | 4 ++--
 fs/eventpoll.c                          | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst
index f48277a0a850..f7fe45e69c41 100644
--- a/Documentation/admin-guide/sysctl/fs.rst
+++ b/Documentation/admin-guide/sysctl/fs.rst
@@ -380,5 +380,5 @@ This configuration option sets the maximum number of "watches" that are
 allowed for each user.
 Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
 on a 64bit one.
-The current default value for  max_user_watches  is the 1/32 of the available
-low memory, divided for the "watch" cost in bytes.
+The current default value for  max_user_watches  is the 1/16 (6.25%) of the
+available low memory, divided for the "watch" cost in bytes.
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a829af074eb5..de9ef8f6d0b2 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2352,9 +2352,9 @@ static int __init eventpoll_init(void)
 
 	si_meminfo(&si);
 	/*
-	 * Allows top 4% of lomem to be allocated for epoll watches (per user).
+	 * Allows top 6.25% of lomem to be allocated for epoll watches (per user).
 	 */
-	max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
+	max_user_watches = (((si.totalram - si.totalhigh) / 16) << PAGE_SHIFT) /
 		EP_ITEM_COST;
 	BUG_ON(max_user_watches < 0);
 
-- 
2.25.1