kdat: Remove tcp_max_rshare

TCP code doesn't need one any longer.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/include/kerndat.h

@@ -25,7 +25,6 @@ enum pagemap_func {
 
 struct kerndat_s {
 	dev_t shmem_dev;
-	int tcp_max_rshare;
 	int last_cap;
 	u64 zero_page_pfn;
 	bool has_dirty_track;

criu/kerndat.c

@@ -24,23 +24,6 @@
 #include "syscall-codes.h"
 
 struct kerndat_s kdat = {
-	/*
-	 * TCP send receive buffers are calculated
-	 * dynamically by the kernel taking into account
-	 * the size of memory present on the machine.
-	 *
-	 * On machines with huge amount of memory it grants
-	 * up to 4M for sendding buffer and 6M for receiving.
-	 * But in turn for low mem machines these limits
-	 * are quite small down to 16K for sending and
-	 * 87380 for receiving.
-	 *
-	 * We will find out precise limits in tcp_read_sysctl_limits
-	 * but by default lets stick for small data to not fail
-	 * on restore: better to slowdown restore procedure than
-	 * failing completely.
-	 */
-	.tcp_max_rshare = 87380,
 };
 
 static int check_pagemap(void)
@@ -305,44 +288,6 @@ no_dt:
 	return 0;
 }
 
-/*
- * Strictly speaking, if there is a machine with huge amount
- * of memory, we're allowed to send up to 4M and read up to
- * 6M of tcp data at once. But we will figure out precise size
- * of a limit a bit later when restore starts.
- *
- * Meanwhile set it up to 2M and 3M, which is safe enough to
- * proceed without errors.
- */
-
-static int tcp_read_sysctl_limits(void)
-{
-	u32 vect[3] = { };
-	int ret;
-
-	struct sysctl_req req[] = {
-		{ "net/ipv4/tcp_rmem", &vect, CTL_U32A(ARRAY_SIZE(vect)), CTL_FLAGS_OPTIONAL },
-	};
-
-	/*
-	 * Lets figure out which exactly amount of memory is
-	 * availabe for send/read queues on restore.
-	 */
-	ret = sysctl_op(req, ARRAY_SIZE(req), CTL_READ, 0);
-	if (ret || vect[0] == 0) {
-		pr_warn("TCP mem sysctls are not available. Using defaults.\n");
-		goto out;
-	}
-
-	kdat.tcp_max_rshare = min(kdat.tcp_max_rshare, (int)vect[2]);
-
-	if (kdat.tcp_max_rshare < 128)
-		pr_warn("The memory limits for TCP queues are suspiciously small\n");
-out:
-	pr_debug("TCP recv queue memory limit is %d\n", kdat.tcp_max_rshare);
-	return 0;
-}
-
 /* The page frame number (PFN) is constant for the zero page */
 static int init_zero_page_pfn()
 {
@@ -538,8 +483,6 @@ int kerndat_init_rst(void)
 	 */
 
 	ret = check_pagemap();
-	if (!ret)
-		ret = tcp_read_sysctl_limits();
 	if (!ret)
 		ret = get_last_cap();
 	if (!ret)