ext4: create a new BH_Verified flag to avoid unnecessary metadata validation

Create a new BH_Verified flag to indicate that we've verified all the
data in a buffer_head for correctness.  This allows us to bypass
expensive verification steps when they are not necessary without
missing them when they are.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 28 insertions, 9 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index abcdeab67f5..8c1334ee8c7 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -412,6 +412,26 @@ int ext4_ext_check_inode(struct inode *inode)
         return ext4_ext_check(inode, ext_inode_hdr(inode), ext_depth(inode));
 }
 
+static int __ext4_ext_check_block(const char *function, unsigned int line,
+                                  struct inode *inode,
+                                  struct ext4_extent_header *eh,
+                                  int depth,
+                                  struct buffer_head *bh)
+{
+        int ret;
+
+        if (buffer_verified(bh))
+                return 0;
+        ret = ext4_ext_check(inode, eh, depth);
+        if (ret)
+                return ret;
+        set_buffer_verified(bh);
+        return ret;
+}
+
+#define ext4_ext_check_block(inode, eh, depth, bh)      \
+        __ext4_ext_check_block(__func__, __LINE__, inode, eh, depth, bh)
+
 #ifdef EXT_DEBUG
 static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
 {
@@ -668,8 +688,6 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
         i = depth;
         /* walk through the tree */
         while (i) {
-                int need_to_validate = 0;
-
                 ext_debug("depth %d: num %d, max %d\n",
                           ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
 
@@ -688,8 +706,6 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
                                 put_bh(bh);
                                 goto err;
                         }
-                        /* validate the extent entries */
-                        need_to_validate = 1;
                 }
                 eh = ext_block_hdr(bh);
                 ppos++;
@@ -703,7 +719,7 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
                 path[ppos].p_hdr = eh;
                 i--;
 
-                if (need_to_validate && ext4_ext_check(inode, eh, i))
+                if (ext4_ext_check_block(inode, eh, i, bh))
                         goto err;
         }
 
@@ -1344,7 +1360,8 @@ got_index:
                         return -EIO;
                 eh = ext_block_hdr(bh);
                 /* subtract from p_depth to get proper eh_depth */
-                if (ext4_ext_check(inode, eh, path->p_depth - depth)) {
+                if (ext4_ext_check_block(inode, eh,
+                                         path->p_depth - depth, bh)) {
                         put_bh(bh);
                         return -EIO;
                 }
@@ -1357,7 +1374,7 @@ got_index:
         if (bh == NULL)
                 return -EIO;
         eh = ext_block_hdr(bh);
-        if (ext4_ext_check(inode, eh, path->p_depth - depth)) {
+        if (ext4_ext_check_block(inode, eh, path->p_depth - depth, bh)) {
                 put_bh(bh);
                 return -EIO;
         }
@@ -2644,8 +2661,8 @@ cont:
                                 err = -EIO;
                                 break;
                         }
-                        if (ext4_ext_check(inode, ext_block_hdr(bh),
-                                                        depth - i - 1)) {
+                        if (ext4_ext_check_block(inode, ext_block_hdr(bh),
+                                                        depth - i - 1, bh)) {
                                 err = -EIO;
                                 break;
                         }
diff --git a/include/linux/jbd_common.h b/include/linux/jbd_common.h
index 6230f8556a4..6133679bc4c 100644
--- a/include/linux/jbd_common.h
+++ b/include/linux/jbd_common.h
@@ -12,6 +12,7 @@ enum jbd_state_bits {
         BH_State,               /* Pins most journal_head state */
         BH_JournalHead,         /* Pins bh->b_private and jh->b_bh */
         BH_Unshadow,            /* Dummy bit, for BJ_Shadow wakeup filtering */
+        BH_Verified,            /* Metadata block has been verified ok */
         BH_JBDPrivateStart,     /* First bit available for private use by FS */
 };
 
@@ -24,6 +25,7 @@ TAS_BUFFER_FNS(Revoked, revoked)
 BUFFER_FNS(RevokeValid, revokevalid)
 TAS_BUFFER_FNS(RevokeValid, revokevalid)
 BUFFER_FNS(Freed, freed)
+BUFFER_FNS(Verified, verified)
 
 static inline struct buffer_head *jh2bh(struct journal_head *jh)
 {