From 92890123749bafc317bbfacbe0a62ce08d78efb7 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Sun, 8 Nov 2020 22:59:31 -0500 Subject: [PATCH] inotify: Increase default inotify.max_user_watches limit to 1048576 The default value of inotify.max_user_watches sysctl parameter was set to 8192 since the introduction of the inotify feature in 2005 by commit 0eeca28300df ("[PATCH] inotify"). Today this value is just too small for many modern usage. As a result, users have to explicitly set it to a larger value to make it work. After some searching around the web, these are the inotify.max_user_watches values used by some projects: - vscode: 524288 - dropbox support: 100000 - users on stackexchange: 12228 - lsyncd user: 2000000 - code42 support: 1048576 - monodevelop: 16384 - tectonic: 524288 - openshift origin: 65536 Each watch point adds an inotify_inode_mark structure to an inode to be watched. It also pins the watched inode. Modeled after the epoll.max_user_watches behavior to adjust the default value according to the amount of addressable memory available, make inotify.max_user_watches behave in a similar way to make it use no more than 1% of addressable memory within the range [8192, 1048576]. We estimate the amount of memory used by inotify mark to size of inotify_inode_mark plus two times the size of struct inode (we double the inode size to cover the additional filesystem private inode part). That means that a 64-bit system with 128GB or more memory will likely have the maximum value of 1048576 for inotify.max_user_watches. This default should be big enough for most use cases. Link: https://lore.kernel.org/r/20201109035931.4740-1-longman@redhat.com Reviewed-by: Amir Goldstein Signed-off-by: Waiman Long Signed-off-by: Jan Kara --- fs/notify/inotify/inotify_user.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index 186722ba3894..24d17028375e 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -37,6 +37,15 @@ #include +/* + * An inotify watch requires allocating an inotify_inode_mark structure as + * well as pinning the watched inode. Doubling the size of a VFS inode + * should be more than enough to cover the additional filesystem inode + * size increase. + */ +#define INOTIFY_WATCH_COST (sizeof(struct inotify_inode_mark) + \ + 2 * sizeof(struct inode)) + /* configurable via /proc/sys/fs/inotify/ */ static int inotify_max_queued_events __read_mostly; @@ -801,6 +810,18 @@ out: */ static int __init inotify_user_setup(void) { + unsigned long watches_max; + struct sysinfo si; + + si_meminfo(&si); + /* + * Allow up to 1% of addressable memory to be allocated for inotify + * watches (per user) limited to the range [8192, 1048576]. + */ + watches_max = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) / + INOTIFY_WATCH_COST; + watches_max = clamp(watches_max, 8192UL, 1048576UL); + BUILD_BUG_ON(IN_ACCESS != FS_ACCESS); BUILD_BUG_ON(IN_MODIFY != FS_MODIFY); BUILD_BUG_ON(IN_ATTRIB != FS_ATTRIB); @@ -827,7 +848,7 @@ static int __init inotify_user_setup(void) inotify_max_queued_events = 16384; init_user_ns.ucount_max[UCOUNT_INOTIFY_INSTANCES] = 128; - init_user_ns.ucount_max[UCOUNT_INOTIFY_WATCHES] = 8192; + init_user_ns.ucount_max[UCOUNT_INOTIFY_WATCHES] = watches_max; return 0; }