Linux 3.1 compat, shrink_*cache_memory

As of Linux 3.1 the shrink_dcache_memory and shrink_icache_memory
functions have been removed.  This same task is now accomplished
more cleanly with per super block shrinkers.  This unfortunately
leaves us no easy way to support the dnlc_reduce_cache() function.

This support has always been entirely optional.  So when no
reasonable interface is available allow the dnlc_reduce_cache()
function to effectively become a no-op.

The downside of this change is that it will prevent the zfs arc
meta data limts from being enforced.  However, the current zfs
implementation in this regard is already flawed and needs to
be reworked.  If the arc needs to enfore a meta data limit it
will need to be extended to coordinate directly with the zpl.
This will allow us to drop all this compatibility code and get
more fine grained control over the cache management.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #52

diff --git a/include/linux/mm_compat.h b/include/linux/mm_compat.h
index 173acd4345023836fe1b8e73d5a0edae3a00d820..b375f9b39be05a29073a5b91e779c11f6e0a4c8c 100644 (file)
--- a/include/linux/mm_compat.h
+++ b/include/linux/mm_compat.h
@@ -93,16 +93,37 @@ extern shrink_dcache_memory_t shrink_dcache_memory_fn;
 #  define shrink_dcache_memory(nr, gfp)                                      \
 ({                                                                           \
        struct shrink_control sc = { .nr_to_scan = nr, .gfp_mask = gfp };    \
-       shrink_dcache_memory_fn(NULL, &sc);                                  \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_dcache_memory_fn)                                         \
+               __ret__ = shrink_dcache_memory_fn(NULL, &sc);                \
+                                                                             \
+       __ret__;                                                             \
 })
 # elif defined(HAVE_3ARGS_SHRINKER_CALLBACK)
 typedef int (*shrink_dcache_memory_t)(struct shrinker *, int, gfp_t);
 extern shrink_dcache_memory_t shrink_dcache_memory_fn;
-#  define shrink_dcache_memory(nr, gfp)        shrink_dcache_memory_fn(NULL, nr, gfp)
+#  define shrink_dcache_memory(nr, gfp)                                      \
+({                                                                           \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_dcache_memory_fn)                                         \
+               __ret__ = shrink_dcache_memory_fn(NULL, nr, gfp);            \
+                                                                             \
+       __ret__;                                                             \
+})
 # else
 typedef int (*shrink_dcache_memory_t)(int, gfp_t);
 extern shrink_dcache_memory_t shrink_dcache_memory_fn;
-#  define shrink_dcache_memory(nr, gfp)        shrink_dcache_memory_fn(nr, gfp)
+#  define shrink_dcache_memory(nr, gfp)                                      \
+({                                                                           \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_dcache_memory_fn)                                         \
+               __ret__ = shrink_dcache_memory_fn(nr, gfp);                  \
+                                                                             \
+       __ret__;                                                             \
+})
 # endif /* HAVE_3ARGS_SHRINKER_CALLBACK */
 #endif /* HAVE_SHRINK_DCACHE_MEMORY */
 
@@ -120,16 +141,37 @@ extern shrink_icache_memory_t shrink_icache_memory_fn;
 #  define shrink_icache_memory(nr, gfp)                                      \
 ({                                                                           \
        struct shrink_control sc = { .nr_to_scan = nr, .gfp_mask = gfp };    \
-       shrink_icache_memory_fn(NULL, &sc);                                  \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_icache_memory_fn)                                         \
+               __ret__ = shrink_icache_memory_fn(NULL, &sc);                \
+                                                                             \
+       __ret__;                                                             \
 })
 # elif defined(HAVE_3ARGS_SHRINKER_CALLBACK)
 typedef int (*shrink_icache_memory_t)(struct shrinker *, int, gfp_t);
 extern shrink_icache_memory_t shrink_icache_memory_fn;
-#  define shrink_icache_memory(nr, gfp)        shrink_icache_memory_fn(NULL, nr, gfp)
+#  define shrink_icache_memory(nr, gfp)                                      \
+({                                                                           \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_icache_memory_fn)                                         \
+               __ret__ = shrink_icache_memory_fn(NULL, nr, gfp);            \
+                                                                             \
+       __ret__;                                                             \
+})
 # else
 typedef int (*shrink_icache_memory_t)(int, gfp_t);
 extern shrink_icache_memory_t shrink_icache_memory_fn;
-#  define shrink_icache_memory(nr, gfp)        shrink_icache_memory_fn(nr, gfp)
+#  define shrink_icache_memory(nr, gfp)                                      \
+({                                                                           \
+       int __ret__ = 0;                                                     \
+                                                                             \
+       if (shrink_icache_memory_fn)                                         \
+               __ret__ = shrink_icache_memory_fn(nr, gfp);                  \
+                                                                             \
+       __ret__;                                                             \
+})
 # endif /* HAVE_3ARGS_SHRINKER_CALLBACK */
 #endif /* HAVE_SHRINK_ICACHE_MEMORY */
 

diff --git a/module/spl/spl-kmem.c b/module/spl/spl-kmem.c
index b3c054a958af74976aa2ac6fcbc7ad29a352d711..1d2fa90539375c22836852ad7bb9d8363c14ebfe 100644 (file)
--- a/module/spl/spl-kmem.c
+++ b/module/spl/spl-kmem.c
@@ -2123,21 +2123,15 @@ spl_kmem_init_kallsyms_lookup(void)
 #endif /* HAVE_INVALIDATE_INODES */
 
 #ifndef HAVE_SHRINK_DCACHE_MEMORY
+       /* When shrink_dcache_memory_fn == NULL support is disabled */
        shrink_dcache_memory_fn = (shrink_dcache_memory_t)
-       spl_kallsyms_lookup_name("shrink_dcache_memory");
-       if (!shrink_dcache_memory_fn) {
-               printk(KERN_ERR "Error: Unknown symbol shrink_dcache_memory\n");
-               return -EFAULT;
-       }
+               spl_kallsyms_lookup_name("shrink_dcache_memory");
 #endif /* HAVE_SHRINK_DCACHE_MEMORY */
 
 #ifndef HAVE_SHRINK_ICACHE_MEMORY
+       /* When shrink_icache_memory_fn == NULL support is disabled */
        shrink_icache_memory_fn = (shrink_icache_memory_t)
-       spl_kallsyms_lookup_name("shrink_icache_memory");
-       if (!shrink_icache_memory_fn) {
-               printk(KERN_ERR "Error: Unknown symbol shrink_icache_memory\n");
-               return -EFAULT;
-       }
+               spl_kallsyms_lookup_name("shrink_icache_memory");
 #endif /* HAVE_SHRINK_ICACHE_MEMORY */
 
        return 0;