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authorAndrew Morton <akpm@linux-foundation.org>2009-02-04 15:12:06 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-02-05 12:56:47 -0800
commit60fd760fb9ff7034360bab7137c917c0330628c2 (patch)
tree2498b0456b49dc0f4e7db34a9c1d3858e2b5eaf9 /kernel/sys.c
parenta68e61e8ff2d46327a37b69056998b47745db6fa (diff)
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revert "rlimit: permit setting RLIMIT_NOFILE to RLIM_INFINITY"
Revert commit 0c2d64fb6cae9aae480f6a46cfe79f8d7d48b59f because it causes (arguably poorly designed) existing userspace to spend interminable periods closing billions of not-open file descriptors. We could bring this back, with some sort of opt-in tunable in /proc, which defaults to "off". Peter's alanysis follows: : I spent several hours trying to get to the bottom of a serious : performance issue that appeared on one of our servers after upgrading to : 2.6.28. In the end it's what could be considered a userspace bug that : was triggered by a change in 2.6.28. Since this might also affect other : people I figured I'd at least document what I found here, and maybe we : can even do something about it: : : : So, I upgraded some of debian.org's machines to 2.6.28.1 and immediately : the team maintaining our ftp archive complained that one of their : scripts that previously ran in a few minutes still hadn't even come : close to being done after an hour or so. Downgrading to 2.6.27 fixed : that. : : Turns out that script is forking a lot and something in it or python or : whereever closes all the file descriptors it doesn't want to pass on. : That is, it starts at zero and goes up to ulimit -n/RLIMIT_NOFILE and : closes them all with a few exceptions. : : Turns out that takes a long time when your limit -n is now 2^20 (1048576). : : With 2.6.27.* the ulimit -n was the standard 1024, but with 2.6.28 it is : now a thousand times that. : : 2.6.28 included a patch titled "rlimit: permit setting RLIMIT_NOFILE to : RLIM_INFINITY" (0c2d64fb6cae9aae480f6a46cfe79f8d7d48b59f)[1] that : allows, as the title implies, to set the limit for number of files to : infinity. : : Closer investigation showed that the broken default ulimit did not apply : to "system" processes (like stuff started from init). In the end I : could establish that all processes that passed through pam_limit at one : point had the bad resource limit. : : Apparently the pam library in Debian etch (4.0) initializes the limits : to some default values when it doesn't have any settings in limit.conf : to override them. Turns out that for nofiles this is RLIM_INFINITY. : Commenting out "case RLIMIT_NOFILE" in pam_limit.c:267 of our pam : package version 0.79-5 fixes that - tho I'm not sure what side effects : that has. : : Debian lenny (the upcoming 5.0 version) doesn't have this issue as it : uses a different pam (version). Reported-by: Peter Palfrader <weasel@debian.org> Cc: Adam Tkac <vonsch@gmail.com> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Cc: <stable@kernel.org> [2.6.28.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sys.c')
-rw-r--r--kernel/sys.c16
1 files changed, 4 insertions, 12 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index e7dc0e10a48..f145c415bc1 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1525,22 +1525,14 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
return -EINVAL;
if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
return -EFAULT;
+ if (new_rlim.rlim_cur > new_rlim.rlim_max)
+ return -EINVAL;
old_rlim = current->signal->rlim + resource;
if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
!capable(CAP_SYS_RESOURCE))
return -EPERM;
-
- if (resource == RLIMIT_NOFILE) {
- if (new_rlim.rlim_max == RLIM_INFINITY)
- new_rlim.rlim_max = sysctl_nr_open;
- if (new_rlim.rlim_cur == RLIM_INFINITY)
- new_rlim.rlim_cur = sysctl_nr_open;
- if (new_rlim.rlim_max > sysctl_nr_open)
- return -EPERM;
- }
-
- if (new_rlim.rlim_cur > new_rlim.rlim_max)
- return -EINVAL;
+ if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
+ return -EPERM;
retval = security_task_setrlimit(resource, &new_rlim);
if (retval)