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Subject[PATCH 04/16] ext4: Create a new BH_Verified flag to avoid unnecessary metadata validation
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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>
---
fs/ext4/ext4.h | 2 ++
fs/ext4/extents.c | 35 ++++++++++++++++++++++++++---------
2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e717dfd..ecb86c2 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2242,10 +2242,12 @@ extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
enum ext4_state_bits {
BH_Uninit /* blocks are allocated but uninitialized on disk */
= BH_JBDPrivateStart,
+ BH_Verified, /* metadata block has been verified ok */
};

BUFFER_FNS(Uninit, uninit)
TAS_BUFFER_FNS(Uninit, uninit)
+BUFFER_FNS(Verified, verified)

/*
* Add new method to test wether block and inode bitmaps are properly
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 57cf568..4ac4303 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -403,6 +403,26 @@ 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)
{
@@ -659,8 +679,6 @@ 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));

@@ -679,8 +697,6 @@ 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++;
@@ -694,7 +710,7 @@ 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;
}

@@ -1350,7 +1366,8 @@ 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;
}
@@ -1363,7 +1380,7 @@ 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;
}
@@ -2591,8 +2608,8 @@ again:
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;
}


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