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Greg Thelen 421348f1ca fs/dcache.c: add cond_resched() to shrink_dcache_parent() 
Call cond_resched() in shrink_dcache_parent() to maintain interactivity.

Before this patch:

	void shrink_dcache_parent(struct dentry * parent)
	{
		while ((found = select_parent(parent, &dispose)) != 0)
			shrink_dentry_list(&dispose);
	}

select_parent() populates the dispose list with dentries which
shrink_dentry_list() then deletes.  select_parent() carefully uses
need_resched() to avoid doing too much work at once.  But neither
shrink_dcache_parent() nor its called functions call cond_resched().  So
once need_resched() is set select_parent() will return single dentry
dispose list which is then deleted by shrink_dentry_list().  This is
inefficient when there are a lot of dentry to process.  This can cause
softlockup and hurts interactivity on non preemptable kernels.

This change adds cond_resched() in shrink_dcache_parent().  The benefit
of this is that need_resched() is quickly cleared so that future calls
to select_parent() are able to efficiently return a big batch of dentry.

These additional cond_resched() do not seem to impact performance, at
least for the workload below.

Here is a program which can cause soft lockup if other system activity
sets need_resched().

	int main()
	{
	        struct rlimit rlim;
	        int i;
	        int f[100000];
	        char buf[20];
	        struct timeval t1, t2;
	        double diff;

	        /* cleanup past run */
	        system("rm -rf x");

	        /* boost nfile rlimit */
	        rlim.rlim_cur = 200000;
	        rlim.rlim_max = 200000;
	        if (setrlimit(RLIMIT_NOFILE, &rlim))
	                err(1, "setrlimit");

	        /* make directory for files */
	        if (mkdir("x", 0700))
	                err(1, "mkdir");

	        if (gettimeofday(&t1, NULL))
	                err(1, "gettimeofday");

	        /* populate directory with open files */
	        for (i = 0; i < 100000; i++) {
	                snprintf(buf, sizeof(buf), "x/%d", i);
	                f[i] = open(buf, O_CREAT);
	                if (f[i] == -1)
	                        err(1, "open");
	        }

	        /* close some of the files */
	        for (i = 0; i < 85000; i++)
	                close(f[i]);

	        /* unlink all files, even open ones */
	        system("rm -rf x");

	        if (gettimeofday(&t2, NULL))
	                err(1, "gettimeofday");

	        diff = (((double)t2.tv_sec * 1000000 + t2.tv_usec) -
	                ((double)t1.tv_sec * 1000000 + t1.tv_usec));

	        printf("done: %g elapsed\n", diff/1e6);
	        return 0;
	}

Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2013-04-30 17:04:00 -07:00
..
9p fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
adfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
affs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
afs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
autofs4 fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
befs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-04-30 09:36:50 -07:00
bfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
btrfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2013-04-14 10:52:54 -07:00
cachefiles FS-Cache: Mark cancellation of in-progress operation 2012-12-20 22:34:00 +00:00
ceph fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
cifs cifs: Allow passwords which begin with a delimitor 2013-04-10 15:54:14 -05:00
coda fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
configfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
cramfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
debugfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
devpts fs: Limit sys_mount to only request filesystem modules (Part 2). 2013-03-07 01:08:55 -08:00
dlm hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
ecryptfs ecryptfs: close rmmod race 2013-04-09 14:08:16 -04:00
efs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
exofs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
exportfs hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
ext2 ext2: Fix BUG_ON in evict() on inode deletion 2013-03-13 15:23:44 +01:00
ext3 mm: make snapshotting pages for stable writes a per-bio operation 2013-04-29 15:54:33 -07:00
ext4 ext4: fix big-endian bugs which could cause fs corruptions 2013-04-03 12:37:17 -04:00
f2fs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-04-30 09:36:50 -07:00
fat fat (exportfs): rebuild directory-inode if fat_dget() 2013-04-29 18:28:41 -07:00
freevxfs fs: Readd the fs module aliases. 2013-03-12 18:55:21 -07:00
fscache fs/fscache/stats.c: fix memory leak 2013-04-29 15:54:27 -07:00
fuse fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
gfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-04-30 09:36:50 -07:00
hfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
hfsplus hfsplus: fix potential overflow in hfsplus_file_truncate() 2013-04-17 16:10:45 -07:00
hostfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2013-03-13 15:47:50 -07:00
hpfs fs: Limit sys_mount to only request filesystem modules. (Part 3) 2013-03-11 07:09:48 -07:00
hppfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
hugetlbfs hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) 2013-04-17 16:10:44 -07:00
isofs fs: Readd the fs module aliases. 2013-03-12 18:55:21 -07:00
jbd fs/buffer.c: remove unnecessary init operation after allocating buffer_head. 2013-04-29 15:54:39 -07:00
jbd2 fs/buffer.c: remove unnecessary init operation after allocating buffer_head. 2013-04-29 15:54:39 -07:00
jffs2 fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
jfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
lockd Merge branch 'for-3.9' of git://linux-nfs.org/~bfields/linux 2013-02-28 18:02:55 -08:00
logfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
minix fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
ncpfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
nfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-04-30 09:36:50 -07:00
nfs_common nfs_common: Update the translation between nfsv3 acls linux posix acls 2013-02-13 06:15:14 -08:00
nfsd nfsd: convert nfs4_alloc_stid() to use idr_alloc_cyclic() 2013-04-29 18:28:41 -07:00
nilfs2 fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
nls
…
notify inotify: invalid mask should return a error number but not set it 2013-04-30 17:04:00 -07:00
ntfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
ocfs2 ocfs2/dlm: remove redundant null pointer check 2013-04-29 15:54:27 -07:00
omfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
openpromfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
proc Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:15:40 -07:00
pstore A few fixes to reduce places where pstore might hang 2013-02-21 09:38:18 -08:00
qnx4 fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
qnx6 fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
quota quota: add missing use of dq_data_lock in __dquot_initialize 2013-03-11 22:05:56 +01:00
ramfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
reiserfs reiserfs: Fix warning and inode leak when deleting inode with xattrs 2013-03-29 17:08:43 +01:00
romfs fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
squashfs fs: Limit sys_mount to only request filesystem modules. (Part 3) 2013-03-11 07:09:48 -07:00
sysfs sysfs: check if one entry has been removed before freeing 2013-04-05 15:35:52 -07:00
sysv fs: Readd the fs module aliases. 2013-03-12 18:55:21 -07:00
ubifs UBIFS: make space fixup work in the remount case 2013-03-14 11:20:22 +02:00
udf fs: Limit sys_mount to only request filesystem modules. (Part 3) 2013-03-11 07:09:48 -07:00
ufs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-04-30 09:36:50 -07:00
xfs - Fix for a potential infinite loop which was introduced in 4d559a3bcb 2013-03-19 15:17:40 -07:00
Kconfig fuse: Move CUSE Kconfig entry from fs/Kconfig into fs/fuse/Kconfig 2013-01-17 13:08:45 +01:00
Kconfig.binfmt
…
Makefile fs: don't compile in drop_caches.c when CONFIG_SYSCTL=n 2013-04-29 15:54:33 -07:00
aio.c aio: fix possible invalid memory access when DEBUG is enabled 2013-04-26 07:56:18 -07:00
anon_inodes.c get_empty_filp()/alloc_file() leave both ->f_pos and ->f_version zero 2013-02-26 02:46:11 -05:00
attr.c userns: Allow chown and setgid preservation 2012-11-20 04:17:24 -08:00
bad_inode.c lseek: the "whence" argument is called "whence" 2012-12-17 17:15:12 -08:00
binfmt_aout.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
binfmt_elf.c fs/binfmt_elf.c: fix hugetlb memory check in vma_dump_size() 2013-04-17 16:10:44 -07:00
binfmt_elf_fdpic.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
binfmt_em86.c exec: use -ELOOP for max recursion depth 2012-12-17 17:15:23 -08:00
binfmt_flat.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
binfmt_misc.c fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
binfmt_script.c exec: do not leave bprm->interp on stack 2012-12-20 17:40:19 -08:00
binfmt_som.c get rid of pt_regs argument of ->load_binary() 2012-11-28 21:53:38 -05:00
bio-integrity.c
…
bio.c Revert "block: add missing block_bio_complete() tracepoint" 2013-04-18 09:00:26 -07:00
block_dev.c fs/block_dev.c: no need to check inode->i_bdev in bd_forget() 2013-04-30 17:04:00 -07:00
buffer.c fs/buffer.c: remove unnecessary init operation after allocating buffer_head. 2013-04-29 15:54:39 -07:00
char_dev.c char_dev: pin parent kobject 2012-10-22 08:50:37 +03:00
compat.c Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys 2013-03-12 11:05:45 -07:00
compat_binfmt_elf.c
…
compat_ioctl.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
coredump.c coredump: remove redundant defines for dumpable states 2013-02-27 19:10:11 -08:00
coredump.h
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dcache.c fs/dcache.c: add cond_resched() to shrink_dcache_parent() 2013-04-30 17:04:00 -07:00
dcookies.c
…
direct-io.c direct-io: submit bio after boundary buffer is added to it 2013-04-29 15:54:29 -07:00
drop_caches.c
…
eventfd.c fs, eventfd: add procfs fdinfo helper 2012-12-17 17:15:27 -08:00
eventpoll.c epoll: prevent missed events on EPOLL_CTL_MOD 2013-01-02 09:16:43 -08:00
exec.c mm: allow arch code to control the user page table ceiling 2013-04-29 15:54:34 -07:00
fcntl.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
fhandle.c Merge branch 'for-3.8' of git://linux-nfs.org/~bfields/linux 2012-12-20 14:04:11 -08:00
fifo.c
…
file.c locking: Various static lock initializer fixes 2013-02-19 08:42:45 +01:00
file_table.c cache the value of file_inode() in struct file 2013-03-01 19:48:30 -05:00
filesystems.c fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
fs-writeback.c 2 writeback fixes 2013-02-28 13:21:44 -08:00
fs_struct.c constify path_get/path_put and fs_struct.c stuff 2013-03-01 23:51:07 -05:00
generic_acl.c
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inode.c vfs: Revert spurious fix to spinning prevention in prune_icache_sb 2013-04-13 16:13:55 -07:00
internal.h Don't bother with redoing rw_verify_area() from default_file_splice_from() 2013-03-21 13:11:11 -04:00
ioctl.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
ioprio.c
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libfs.c vfs: drop vmtruncate 2012-12-20 18:46:29 -05:00
locks.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
mbcache.c
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mount.h proc: Usable inode numbers for the namespace file descriptors. 2012-11-20 04:19:49 -08:00
mpage.c
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namei.c vfs: don't BUG_ON() if following a /proc fd pseudo-symlink results in a symlink 2013-03-08 09:03:07 -08:00
namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-04-09 12:22:49 -07:00
no-block.c
…
open.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-03-03 13:23:03 -08:00
pipe.c vfs: fix pipe counter breakage 2013-03-12 08:29:17 -07:00
pnode.c vfs: Carefully propogate mounts across user namespaces 2013-03-27 07:50:05 -07:00
pnode.h vfs: Carefully propogate mounts across user namespaces 2013-03-27 07:50:05 -07:00
posix_acl.c
…
proc_namespace.c
…
read_write.c fs/read_write.c: fix generic_file_llseek() comment 2013-04-29 15:54:28 -07:00
read_write.h
…
readdir.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
select.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
seq_file.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-03-03 13:23:03 -08:00
signalfd.c fs, epoll: add procfs fdinfo helper 2012-12-17 17:15:27 -08:00
splice.c Don't bother with redoing rw_verify_area() from default_file_splice_from() 2013-03-21 13:11:11 -04:00
stack.c
…
stat.c switch vfs_getattr() to struct path 2013-02-26 02:46:08 -05:00
statfs.c vfs: fix user_statfs to retry once on ESTALE errors 2012-12-20 18:50:07 -05:00
super.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
sync.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
timerfd.c compat: restore timerfd settime and gettime compat syscalls 2013-03-02 09:35:13 -05:00
utimes.c vfs: allow utimensat() calls to retry once on an ESTALE error 2012-12-20 18:50:08 -05:00
xattr.c vfs: make lremovexattr retry once on ESTALE error 2012-12-20 18:50:11 -05:00
xattr_acl.c userns: Fix posix_acl_file_xattr_userns gid conversion 2012-10-12 13:16:48 -07:00