udf: reduce stack usage of udf_load_pvoldesc

Allocate strings with kmalloc.

Checkstack output:
Before: udf_process_sequence:      712
After:  udf_process_sequence:      200

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 25 insertions, 11 deletions

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 627558213746..8364b1719158 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -902,14 +902,23 @@ static int udf_find_fileset(struct super_block *sb,
 static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
 {
         struct primaryVolDesc *pvoldesc;
-        struct ustr instr;
-        struct ustr outstr;
+        struct ustr *instr, *outstr;
         struct buffer_head *bh;
         uint16_t ident;
+        int ret = 1;
+
+        instr = kmalloc(sizeof(struct ustr), GFP_NOFS);
+        if (!instr)
+                return 1;
+
+        outstr = kmalloc(sizeof(struct ustr), GFP_NOFS);
+        if (!outstr)
+                goto out1;
 
         bh = udf_read_tagged(sb, block, block, &ident);
         if (!bh)
-                return 1;
+                goto out2;
+
         BUG_ON(ident != TAG_IDENT_PVD);
 
         pvoldesc = (struct primaryVolDesc *)bh->b_data;
@@ -925,20 +934,25 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
 #endif
         }
 
-        if (!udf_build_ustr(&instr, pvoldesc->volIdent, 32))
-                if (udf_CS0toUTF8(&outstr, &instr)) {
-                        strncpy(UDF_SB(sb)->s_volume_ident, outstr.u_name,
-                                outstr.u_len > 31 ? 31 : outstr.u_len);
+        if (!udf_build_ustr(instr, pvoldesc->volIdent, 32))
+                if (udf_CS0toUTF8(outstr, instr)) {
+                        strncpy(UDF_SB(sb)->s_volume_ident, outstr->u_name,
+                                outstr->u_len > 31 ? 31 : outstr->u_len);
                         udf_debug("volIdent[] = '%s'\n",
                                         UDF_SB(sb)->s_volume_ident);
                 }
 
-        if (!udf_build_ustr(&instr, pvoldesc->volSetIdent, 128))
-                if (udf_CS0toUTF8(&outstr, &instr))
-                        udf_debug("volSetIdent[] = '%s'\n", outstr.u_name);
+        if (!udf_build_ustr(instr, pvoldesc->volSetIdent, 128))
+                if (udf_CS0toUTF8(outstr, instr))
+                        udf_debug("volSetIdent[] = '%s'\n", outstr->u_name);
 
         brelse(bh);
-        return 0;
+        ret = 0;
+out2:
+        kfree(outstr);
+out1:
+        kfree(instr);
+        return ret;
 }
 
 static int udf_load_metadata_files(struct super_block *sb, int partition)