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This might be reassigned to kernel, as it is broken since rhel7
kernel commit 06c42e3f5156a048a2e50ec013646bfdda916688 that does
some shortcuts, with the side effect of not triggering the probes.
From my understanding of the semantics, the new patch should not
have the "!" operator, so, fixing this issue only on rhel7 would
require this patch:
"""
--- /usr/share/systemtap/tapset/linux/vfs.stp.orig
+++ /usr/share/systemtap/tapset/linux/vfs.stp
@@ -862,8 +862,8 @@
}
probe vfs.add_to_page_cache =
- kernel.function("add_to_page_cache_locked") !,
- kernel.function("add_to_page_cache")
+ kernel.function("add_to_page_cache_lru"),
+ kernel.function("add_to_page_cache_locked")
{
dev = $mapping->host->i_sb->s_dev
devname = __find_bdevname(dev, $mapping->host->i_sb->s_bdev)
@@ -879,8 +879,8 @@
}
probe vfs.add_to_page_cache.return =
- kernel.function("add_to_page_cache_locked").return !,
- kernel.function("add_to_page_cache").return
+ kernel.function("add_to_page_cache_lru").return,
+ kernel.function("add_to_page_cache_locked").return
{
name = "vfs.add_to_page_cache"
retstr = sprintf("%d", $return)
"""
quick and dirty test case is:
"""
#!/bin/stap
probe vfs.add_to_page_cache {
printf("%s\n", probefunc());
}
"""
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHEA-2018:3168
This might be reassigned to kernel, as it is broken since rhel7 kernel commit 06c42e3f5156a048a2e50ec013646bfdda916688 that does some shortcuts, with the side effect of not triggering the probes. From my understanding of the semantics, the new patch should not have the "!" operator, so, fixing this issue only on rhel7 would require this patch: """ --- /usr/share/systemtap/tapset/linux/vfs.stp.orig +++ /usr/share/systemtap/tapset/linux/vfs.stp @@ -862,8 +862,8 @@ } probe vfs.add_to_page_cache = - kernel.function("add_to_page_cache_locked") !, - kernel.function("add_to_page_cache") + kernel.function("add_to_page_cache_lru"), + kernel.function("add_to_page_cache_locked") { dev = $mapping->host->i_sb->s_dev devname = __find_bdevname(dev, $mapping->host->i_sb->s_bdev) @@ -879,8 +879,8 @@ } probe vfs.add_to_page_cache.return = - kernel.function("add_to_page_cache_locked").return !, - kernel.function("add_to_page_cache").return + kernel.function("add_to_page_cache_lru").return, + kernel.function("add_to_page_cache_locked").return { name = "vfs.add_to_page_cache" retstr = sprintf("%d", $return) """ quick and dirty test case is: """ #!/bin/stap probe vfs.add_to_page_cache { printf("%s\n", probefunc()); } """