It can be useful to make negative dentry limit enformcement a runtime
tuning parameter instead of just a boot time option. This allows system
administrator to disable limit enforcement in normal use, but turn it
on under certain circumstances.
A new /proc/sys/fs/enforce-neg-dentry-limit sysctl parameter is now
added. This is a boolean flag that accept a value of either 0 or 1
for disabling and enabling enforcement of negative dentry limit
respectively.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
Documentation/sysctl/fs.txt | 11 +++++++++++
fs/dcache.c | 4 +++-
include/linux/dcache.h | 4 ++++
kernel/sysctl.c | 11 +++++++++++
4 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
index a8e3f1f..ef8fd32 100644
--- a/Documentation/sysctl/fs.txt
+++ b/Documentation/sysctl/fs.txt
@@ -24,6 +24,7 @@ Currently, these files are in /proc/sys/fs:
- dentry-state
- dquot-max
- dquot-nr
+- enforce-neg-dentry-limit
- file-max
- file-nr
- inode-max
@@ -97,6 +98,16 @@ you might want to raise the limit.
==============================================================
+enforce-neg-dentry-limit:
+
+The file enforce-neg-dentry-limit, if present, contains a boolean
+flag (0 or 1) indicating if the negative dentries limit set by
+the "neg_dentry_pc" kernel parameter should be enforced or not.
+If enforced, excess negative dentries over the limit will be killed
+immediately after use.
+
+==============================================================
+
file-max & file-nr:
The value in file-max denotes the maximum number of file-
diff --git a/fs/dcache.c b/fs/dcache.c
index 77910c9..f50886e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -146,7 +146,9 @@ struct dentry_stat_t dentry_stat = {
unlikely(!(sb)->s_root || !((sb)->s_flags & MS_ACTIVE))
#ifdef CONFIG_DCACHE_TRACK_NEG_ENTRY
-static int enforce_neg_dentry_limit __read_mostly;
+int enforce_neg_dentry_limit __read_mostly;
+EXPORT_SYMBOL_GPL(enforce_neg_dentry_limit);
+
static int neg_dentry_pc __read_mostly = NEG_DENTRY_PC_DEFAULT;
static long neg_dentry_percpu_limit __read_mostly;
static long neg_dentry_nfree_init __read_mostly; /* Free pool initial value */
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 69b8cb3..bd7238a0 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -610,4 +610,8 @@ struct name_snapshot {
void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
void release_dentry_name_snapshot(struct name_snapshot *);
+#ifdef CONFIG_DCACHE_TRACK_NEG_ENTRY
+extern int enforce_neg_dentry_limit;
+#endif
+
#endif /* __LINUX_DCACHE_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2d9837c..94f6f6c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1849,6 +1849,17 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write,
.proc_handler = proc_dointvec_minmax,
.extra1 = &one,
},
+#ifdef CONFIG_DCACHE_TRACK_NEG_ENTRY
+ {
+ .procname = "enforce-neg-dentry-limit",
+ .data = &enforce_neg_dentry_limit,
+ .maxlen = sizeof(enforce_neg_dentry_limit),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+#endif
{ }
};
--
1.8.3.1
