From 869764f64df5b2ef2e978c38bd051b39e65cb97e Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Wed, 16 Jun 2010 13:49:25 -0700
Subject: [PATCH 1/2] Add fix-stack-dsl_deleg_get topic branch
Reduce stack usage in dsl_deleg_get, gcc flagged it as consuming a
whopping 1040 bytes or potentially 1/4 of a 4K stack. This patch
moves all the large structures and buffer off the stack and on to
the heap. This includes 2 zap_cursor_t structs each 52 bytes in
size, 2 zap_attribute_t structs each 280 bytes in size, and 1
256 byte char array. The total saves on the stack is 880 bytes
after you account for the 5 new pointers added.
Also the source buffer length has been increased from MAXNAMELEN
to MAXNAMELEN+strlen(MOS_DIR_NAME)+1 as described by the comment in
dsl_dir_name(). A buffer overrun may have been possible with the
slightly smaller buffer.
---
.topdeps | 1 +
.topmsg | 17 +++++++++++++++++
module/zfs/dsl_deleg.c | 43 +++++++++++++++++++++++++-----------------
3 files changed, 44 insertions(+), 17 deletions(-)
create mode 100644 .topdeps
create mode 100644 .topmsg
diff --git a/.topdeps b/.topdeps
new file mode 100644
index 0000000000..1f7391f92b
--- /dev/null
+++ b/.topdeps
@@ -0,0 +1 @@
+master
diff --git a/.topmsg b/.topmsg
new file mode 100644
index 0000000000..9af76c1d4c
--- /dev/null
+++ b/.topmsg
@@ -0,0 +1,17 @@
+From: Brian Behlendorf <behlendorf1@llnl.gov>
+Subject: [PATCH] fix stack dsl_deleg_get
+
+Reduce stack usage in dsl_deleg_get, gcc flagged it as consuming a
+whopping 1040 bytes or potentially 1/4 of a 4K stack. This patch
+moves all the large structures and buffer off the stack and on to
+the heap. This includes 2 zap_cursor_t structs each 52 bytes in
+size, 2 zap_attribute_t structs each 280 bytes in size, and 1
+256 byte char array. The total saves on the stack is 880 bytes
+after you account for the 5 new pointers added.
+
+Also the source buffer length has been increased from MAXNAMELEN
+to MAXNAMELEN+strlen(MOS_DIR_NAME)+1 as described by the comment in
+dsl_dir_name(). A buffer overrun may have been possible with the
+slightly smaller buffer.
+
+Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
diff --git a/module/zfs/dsl_deleg.c b/module/zfs/dsl_deleg.c
index 85490c8d5f..54dbe4aa1e 100644
--- a/module/zfs/dsl_deleg.c
+++ b/module/zfs/dsl_deleg.c
@@ -296,6 +296,9 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
dsl_pool_t *dp;
int error;
objset_t *mos;
+ zap_cursor_t *basezc, *zc;
+ zap_attribute_t *baseza, *za;
+ char *source;
error = dsl_dir_open(ddname, FTAG, &startdd, NULL);
if (error)
@@ -304,15 +307,17 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
dp = startdd->dd_pool;
mos = dp->dp_meta_objset;
+ zc = kmem_alloc(sizeof(zap_cursor_t), KM_SLEEP);
+ za = kmem_alloc(sizeof(zap_attribute_t), KM_SLEEP);
+ basezc = kmem_alloc(sizeof(zap_cursor_t), KM_SLEEP);
+ baseza = kmem_alloc(sizeof(zap_attribute_t), KM_SLEEP);
+ source = kmem_alloc(MAXNAMELEN + strlen(MOS_DIR_NAME) + 1, KM_SLEEP);
VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
rw_enter(&dp->dp_config_rwlock, RW_READER);
for (dd = startdd; dd != NULL; dd = dd->dd_parent) {
- zap_cursor_t basezc;
- zap_attribute_t baseza;
nvlist_t *sp_nvp;
uint64_t n;
- char source[MAXNAMELEN];
if (dd->dd_phys->dd_deleg_zapobj &&
(zap_count(mos, dd->dd_phys->dd_deleg_zapobj,
@@ -323,32 +328,30 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
continue;
}
- for (zap_cursor_init(&basezc, mos,
+ for (zap_cursor_init(basezc, mos,
dd->dd_phys->dd_deleg_zapobj);
- zap_cursor_retrieve(&basezc, &baseza) == 0;
- zap_cursor_advance(&basezc)) {
- zap_cursor_t zc;
- zap_attribute_t za;
+ zap_cursor_retrieve(basezc, baseza) == 0;
+ zap_cursor_advance(basezc)) {
nvlist_t *perms_nvp;
- ASSERT(baseza.za_integer_length == 8);
- ASSERT(baseza.za_num_integers == 1);
+ ASSERT(baseza->za_integer_length == 8);
+ ASSERT(baseza->za_num_integers == 1);
VERIFY(nvlist_alloc(&perms_nvp,
NV_UNIQUE_NAME, KM_SLEEP) == 0);
- for (zap_cursor_init(&zc, mos, baseza.za_first_integer);
- zap_cursor_retrieve(&zc, &za) == 0;
- zap_cursor_advance(&zc)) {
+ for (zap_cursor_init(zc, mos, baseza->za_first_integer);
+ zap_cursor_retrieve(zc, za) == 0;
+ zap_cursor_advance(zc)) {
VERIFY(nvlist_add_boolean(perms_nvp,
- za.za_name) == 0);
+ za->za_name) == 0);
}
- zap_cursor_fini(&zc);
- VERIFY(nvlist_add_nvlist(sp_nvp, baseza.za_name,
+ zap_cursor_fini(zc);
+ VERIFY(nvlist_add_nvlist(sp_nvp, baseza->za_name,
perms_nvp) == 0);
nvlist_free(perms_nvp);
}
- zap_cursor_fini(&basezc);
+ zap_cursor_fini(basezc);
dsl_dir_name(dd, source);
VERIFY(nvlist_add_nvlist(*nvp, source, sp_nvp) == 0);
@@ -356,6 +359,12 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
}
rw_exit(&dp->dp_config_rwlock);
+ kmem_free(source, MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);
+ kmem_free(baseza, sizeof(zap_attribute_t));
+ kmem_free(basezc, sizeof(zap_cursor_t));
+ kmem_free(za, sizeof(zap_attribute_t));
+ kmem_free(zc, sizeof(zap_cursor_t));
+
dsl_dir_close(startdd, FTAG);
return (0);
}
From 2709f5731b33f127af6e5d2852a1f00c02d2a077 Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Wed, 16 Jun 2010 13:49:53 -0700
Subject: [PATCH 2/2] New TopGit dependency: fix-stack-dsl_deleg_get
---
.topdeps | 1 +
1 file changed, 1 insertion(+)
diff --git a/.topdeps b/.topdeps
index a9532822f6..903387bf5f 100644
--- a/.topdeps
+++ b/.topdeps
@@ -17,3 +17,4 @@ fix-metaslab
fix-kstat-xuio
fix-stack-lzjb
fix-stack-dsl_dir_open_spa
+fix-stack-dsl_deleg_get