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https://bugzilla.lustre.org/show_bug.cgi?id=11562
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
the problem is reproducible locally in a SL10.1 environment.
The folling hot fix (with debugging code) fixes the problem.
However it is not tried on buffalo.
diff -u -p -r1.27.40.3.14.3.26.4 symlink.c
--- lustre/llite/symlink.c 16 Nov 2006 19:21:39 -0000
1.27.40.3.14.3.26.4
+++ lustre/llite/symlink.c 18 Jan 2007 10:41:09 -0000
@@ -130,7 +130,7 @@ static LL_FOLLOW_LINK_RETURN_TYPE ll_fol
struct inode *inode = dentry->d_inode;
struct ll_inode_info *lli = ll_i2info(inode);
struct lookup_intent *it = ll_nd2it(nd);
- struct ptlrpc_request *request;
+ struct ptlrpc_request *request = NULL;
int rc;
char *symname;
ENTRY;
@@ -145,6 +145,17 @@ static LL_FOLLOW_LINK_RETURN_TYPE ll_fol
}
CDEBUG(D_VFSTRACE, "VFS Op\n");
+
+ {
+ int dummy = 1;
+ printk("SP x%p lelel = %d\n", &dummy, current->link_count);
+ }
+
+ if (current->link_count > 5) {
+ path_release(nd);
+ GOTO(out, rc = -ELOOP);
+ }
+
A simpler test found which causes stack overflow in a luster client
without the hot fix:
$ ln -sf foo foo
$ ls foo
The debugging code above gives information about how stack usage
grows with each ll_follow_link call:
SP 0xffff810001defb14 lelel = 1
SP 0xffff810001def8c4 lelel = 2
SP 0xffff810001def674 lelel = 3
SP 0xffff810001def424 lelel = 4
SP 0xffff810001def1d4 lelel = 5
SP 0xffff810001deef84 lelel = 6
It means these functions together eat 592 bytes on stack:
link_path_walk
__link_path_walk
do_follow_link
__do_follow_link
__vfs_follow_link
(link_path_walk again)
especially link_path_walk takes 200 bytes and __link_path_walk takes 280
(from checkstack.pl report)
for comparing,
the same functions in the same kernel for i386 arch take:
__link_path_walk: 280
link_path_walk: 200
and stack usage report for newer kernel 2.6.20-rc5 on x86_64:
link_path_walk [vmlinux]: 152
__link_path_walk [vmlinux]: 104
2.6.9-rhel4 and x86_64:
0xffffffff80184f6f link_path_walk: 192
0xffffffff80183f80 __link_path_walk: 136
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