ddt_zap: standardise temp buffer allocations

Always do them on the heap, and when we know how much we need, only that
much.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Sponsored-by: Klara, Inc.
Sponsored-by: iXsystems, Inc.
Closes #15887

diff --git a/module/zfs/ddt_zap.c b/module/zfs/ddt_zap.c
index 6b9d60c5609244d55f4a3fdbc015fe8291f50e9a..0ec3eccb1c144125149e3d523c9ce533cf96b4f8 100644 (file)
--- a/module/zfs/ddt_zap.c
+++ b/module/zfs/ddt_zap.c
@@ -109,24 +109,23 @@ ddt_zap_lookup(objset_t *os, uint64_t object, ddt_entry_t *dde)
        uint64_t one, csize;
        int error;
 
-       cbuf = kmem_alloc(sizeof (dde->dde_phys) + 1, KM_SLEEP);
-
        error = zap_length_uint64(os, object, (uint64_t *)&dde->dde_key,
            DDT_KEY_WORDS, &one, &csize);
        if (error)
-               goto out;
+               return (error);
 
        ASSERT3U(one, ==, 1);
        ASSERT3U(csize, <=, (sizeof (dde->dde_phys) + 1));
 
+       cbuf = kmem_alloc(csize, KM_SLEEP);
+
        error = zap_lookup_uint64(os, object, (uint64_t *)&dde->dde_key,
            DDT_KEY_WORDS, 1, csize, cbuf);
-       if (error)
-               goto out;
+       if (error == 0)
+               ddt_zap_decompress(cbuf, dde->dde_phys, csize,
+                   sizeof (dde->dde_phys));
 
-       ddt_zap_decompress(cbuf, dde->dde_phys, csize, sizeof (dde->dde_phys));
-out:
-       kmem_free(cbuf, sizeof (dde->dde_phys) + 1);
+       kmem_free(cbuf, csize);
 
        return (error);
 }
@@ -141,14 +140,19 @@ ddt_zap_prefetch(objset_t *os, uint64_t object, ddt_entry_t *dde)
 static int
 ddt_zap_update(objset_t *os, uint64_t object, ddt_entry_t *dde, dmu_tx_t *tx)
 {
-       uchar_t cbuf[sizeof (dde->dde_phys) + 1];
-       uint64_t csize;
+       const size_t cbuf_size = sizeof (dde->dde_phys) + 1;
+
+       uchar_t *cbuf = kmem_alloc(cbuf_size, KM_SLEEP);
+
+       uint64_t csize = ddt_zap_compress(dde->dde_phys, cbuf,
+           sizeof (dde->dde_phys), cbuf_size);
+
+       int error = zap_update_uint64(os, object, (uint64_t *)&dde->dde_key,
+           DDT_KEY_WORDS, 1, csize, cbuf, tx);
 
-       csize = ddt_zap_compress(dde->dde_phys, cbuf,
-           sizeof (dde->dde_phys), sizeof (cbuf));
+       kmem_free(cbuf, cbuf_size);
 
-       return (zap_update_uint64(os, object, (uint64_t *)&dde->dde_key,
-           DDT_KEY_WORDS, 1, csize, cbuf, tx));
+       return (error);
 }
 
 static int
@@ -178,9 +182,13 @@ ddt_zap_walk(objset_t *os, uint64_t object, ddt_entry_t *dde, uint64_t *walk)
                zap_cursor_init_serialized(&zc, os, object, *walk);
        }
        if ((error = zap_cursor_retrieve(&zc, &za)) == 0) {
-               uchar_t cbuf[sizeof (dde->dde_phys) + 1];
                uint64_t csize = za.za_num_integers;
+
                ASSERT3U(za.za_integer_length, ==, 1);
+               ASSERT3U(csize, <=, sizeof (dde->dde_phys) + 1);
+
+               uchar_t *cbuf = kmem_alloc(csize, KM_SLEEP);
+
                error = zap_lookup_uint64(os, object, (uint64_t *)za.za_name,
                    DDT_KEY_WORDS, 1, csize, cbuf);
                ASSERT0(error);
@@ -189,6 +197,9 @@ ddt_zap_walk(objset_t *os, uint64_t object, ddt_entry_t *dde, uint64_t *walk)
                            sizeof (dde->dde_phys));
                        dde->dde_key = *(ddt_key_t *)za.za_name;
                }
+
+               kmem_free(cbuf, csize);
+
                zap_cursor_advance(&zc);
                *walk = zap_cursor_serialize(&zc);
        }