pipe: set lower and upper limit on max pages in the pipe page array
We need at least two to guarantee proper POSIX behaviour, so
never allow a smaller limit than that.
Also expose a /proc/sys/fs/pipe-max-pages sysctl file that allows
root to define a sane upper limit. Make it default to 16 times the
default size, which is 16 pages.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8686b0f..c649d1c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -52,6 +52,7 @@
#include <linux/slow-work.h>
#include <linux/perf_event.h>
#include <linux/kprobes.h>
+#include <linux/pipe_fs_i.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
@@ -1423,6 +1424,14 @@
.child = binfmt_misc_table,
},
#endif
+ {
+ .procname = "pipe-max-pages",
+ .data = &pipe_max_pages,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .extra1 = &two,
+ },
/*
* NOTE: do not add new entries to this table unless you have read
* Documentation/sysctl/ctl_unnumbered.txt
