[PATCH xen-unstable] blktap1 -- adapt user space to linux-2.6.18-xen MAX_TAP_DEV (256)

[Laszlo Ersek <lersek@redhat.com>]

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Hi,

as of xen-unstable 22961:c5d121fd35c0 and linux-2.6.18-xen 
1072:9e1f69c2e956, there's a discrepancy between the number of the 
blktap1 devices the kernel and the tools support. This patch intends to 
pull up the tools side to the same limit (256).

While testing the related RHBZ (680407), additional (run time) limits 
were encountered.

One is the fs.aio-max-nr sysctl. A hint is logged about raising it; the 
patch fixes a typo (which is absent from the corresponding blktap2 code) 
in this message.

The other run time limit is one of the four default xenstore quotas. (I 
didn't investigate which one exactly.) Though the quotas can be 
overridden with command line options, the patch quadruples all the 
defaults. In the process I noticed there was a mismatch between the set 
of command line options xenstored accepts and the set it displays as 
usage help; the patch tries to adjust the latter to the former 
(entry-watch --> watch-nb).

I think the patch is small enough not to be split up in a series; please 
pick whichever hunk you deem worthy.

Thanks for considering,
lacos

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diff -r c5d121fd35c0 tools/blktap/drivers/tapaio.c
--- a/tools/blktap/drivers/tapaio.c	Mon Feb 28 16:55:20 2011 +0000
+++ b/tools/blktap/drivers/tapaio.c	Wed Mar 02 13:13:15 2011 +0100
@@ -223,7 +223,7 @@
 				"trying to concurrently use a large number "
 				"of blktap-based disks, you may need to "
 				"increase the system-wide aio request limit. "
-				"(e.g. 'echo echo 1048576 > /proc/sys/fs/"
+				"(e.g. 'echo 1048576 > /proc/sys/fs/"
 				"aio-max-nr')\n");
 		} else {
 			DPRINTF("Couldn't setup AIO context.\n");
diff -r c5d121fd35c0 tools/blktap/lib/blktaplib.h
--- a/tools/blktap/lib/blktaplib.h	Mon Feb 28 16:55:20 2011 +0000
+++ b/tools/blktap/lib/blktaplib.h	Wed Mar 02 13:13:15 2011 +0100
@@ -226,7 +226,7 @@
 
 
 /* Abitrary values, must match the underlying driver... */
-#define MAX_TAP_DEV 100
+#define MAX_TAP_DEV 256
 
 /* Accessing attached data page mappings */
 #define MMAP_PAGES                                              \
diff -r c5d121fd35c0 tools/xenstore/xenstored_core.c
--- a/tools/xenstore/xenstored_core.c	Mon Feb 28 16:55:20 2011 +0000
+++ b/tools/xenstore/xenstored_core.c	Wed Mar 02 13:13:15 2011 +0100
@@ -75,10 +75,10 @@
 	} while (0)
 
 
-int quota_nb_entry_per_domain = 1000;
-int quota_nb_watch_per_domain = 128;
-int quota_max_entry_size = 2048; /* 2K */
-int quota_max_transaction = 10;
+int quota_nb_entry_per_domain = 4000;
+int quota_nb_watch_per_domain = 512;
+int quota_max_entry_size = 8192; /* 8K */
+int quota_max_transaction = 40;
 
 TDB_CONTEXT *tdb_context(struct connection *conn)
 {
@@ -1719,7 +1719,7 @@
 "  --trace-file <file> giving the file for logging, and\n"
 "  --entry-nb <nb>     limit the number of entries per domain,\n"
 "  --entry-size <size> limit the size of entry per domain, and\n"
-"  --entry-watch <nb>  limit the number of watches per domain,\n"
+"  --watch-nb <nb>     limit the number of watches per domain,\n"
 "  --transaction <nb>  limit the number of transaction allowed per domain,\n"
 "  --no-recovery       to request that no recovery should be attempted when\n"
 "                      the store is corrupted (debug only),\n"

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