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Subject[PATCH] Broken NR_RESERVED_FILES

Reserved fd's for superuser doesn't work. Patch for 2.2 is below,
kernel 2.4.x also has this problem, fix is similar. The default
NR_RESERVED_FILES value also had to be increased (e.g. ssh, login
needs 36, ls 16, man 45 fd's, etc).

BTW, I have an updated version of my reserved VM for superuser +
improved/fixed version of Rik's out of memory killer patch for 2.2
here,

http://mlf.linux.rulez.org/mlf/ezaz/reserved_root_vm+oom_killer-5.diff

It fixes the potential deadlock when kernel threads were blocked to
try to free pages - more details about the patch are in a former
email, http://boudicca.tux.org/hypermail/linux-kernel/2000week48/0624.html

Szaka

diff -ur linux-2.2.18pre21/fs/file_table.c linux/fs/file_table.c
--- linux-2.2.18pre21/fs/file_table.c Tue Jan 4 13:12:23 2000
+++ linux/fs/file_table.c Thu Dec 7 13:26:06 2000
@@ -71,30 +71,27 @@
{
static int old_max = 0;
struct file * f;
+ int total_free;

- if (nr_free_files > NR_RESERVED_FILES) {
- used_one:
- f = free_filps;
- remove_filp(f);
- nr_free_files--;
- new_one:
- memset(f, 0, sizeof(*f));
- f->f_count = 1;
- f->f_version = ++global_event;
- f->f_uid = current->fsuid;
- f->f_gid = current->fsgid;
- put_inuse(f);
- return f;
- }
- /*
- * Use a reserved one if we're the superuser
- */
- if (nr_free_files && !current->euid)
- goto used_one;
- /*
- * Allocate a new one if we're below the limit.
- */
- if (nr_files < max_files) {
+ total_free = max_files - nr_files + nr_free_files;
+ if (total_free > NR_RESERVED_FILES || (total_free && !current->euid)) {
+ if (nr_free_files) {
+ used_one:
+ f = free_filps;
+ remove_filp(f);
+ nr_free_files--;
+ new_one:
+ memset(f, 0, sizeof(*f));
+ f->f_count = 1;
+ f->f_version = ++global_event;
+ f->f_uid = current->fsuid;
+ f->f_gid = current->fsgid;
+ put_inuse(f);
+ return f;
+ }
+ /*
+ * Allocate a new one if we're below the limit.
+ */
f = kmem_cache_alloc(filp_cache, SLAB_KERNEL);
if (f) {
nr_files++;
diff -ur linux-2.2.18pre21/include/linux/fs.h linux/include/linux/fs.h
--- linux-2.2.18pre21/include/linux/fs.h Thu Nov 9 08:20:18 2000
+++ linux/include/linux/fs.h Thu Dec 7 11:10:50 2000
@@ -51,7 +51,7 @@
extern int max_super_blocks, nr_super_blocks;

#define NR_FILE 4096 /* this can well be larger on a larger system */
-#define NR_RESERVED_FILES 10 /* reserved for root */
+#define NR_RESERVED_FILES 96 /* reserved for root */
#define NR_SUPER 256

#define MAY_EXEC 1
-
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