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Subject[PATCH 29/49] ext4: Make ext4_get_blocks_wrap take the truncate_mutex early.
Date
From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

When doing a migrate from ext3 to ext4 inode we need to make sure the test
for inode type and walking inode data happens inside lock. To make this
happen move truncate_mutex early before checking the i_flags.


This actually should enable us to remove the verify_chain().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/ext4/extents.c | 9 ++++--
fs/ext4/inode.c | 69 +++++-----------------------------------------
include/linux/ext4_fs.h | 2 +
3 files changed, 16 insertions(+), 64 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8593e59..ec5019f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2129,6 +2129,10 @@ out:
return err ? err : allocated;
}

+/*
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex);
+ */
int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
ext4_lblk_t iblock,
unsigned long max_blocks, struct buffer_head *bh_result,
@@ -2144,7 +2148,6 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
__clear_bit(BH_New, &bh_result->b_state);
ext_debug("blocks %u/%lu requested for inode %u\n",
iblock, max_blocks, inode->i_ino);
- mutex_lock(&EXT4_I(inode)->truncate_mutex);

/* check in cache */
goal = ext4_ext_in_cache(inode, iblock, &newex);
@@ -2318,8 +2321,6 @@ out2:
ext4_ext_drop_refs(path);
kfree(path);
}
- mutex_unlock(&EXT4_I(inode)->truncate_mutex);
-
return err ? err : allocated;
}

@@ -2449,6 +2450,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
* modify 1 super block, 1 block bitmap and 1 group descriptor.
*/
credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;
+ mutex_lock(&EXT4_I(inode)->truncate_mutex)
retry:
while (ret >= 0 && ret < max_blocks) {
block = block + ret;
@@ -2505,6 +2507,7 @@ retry:
if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
goto retry;

+ mutex_unlock(&EXT4_I(inode)->truncate_mutex)
/*
* Time to update the file size.
* Update only when preallocation was requested beyond the file size.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index eaace13..71c7ad0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -243,13 +243,6 @@ static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
p->bh = bh;
}

-static int verify_chain(Indirect *from, Indirect *to)
-{
- while (from <= to && from->key == *from->p)
- from++;
- return (from > to);
-}
-
/**
* ext4_block_to_path - parse the block number into array of offsets
* @inode: inode in question (we are only interested in its superblock)
@@ -348,10 +341,11 @@ static int ext4_block_to_path(struct inode *inode,
* (pointer to last triple returned, *@err == 0)
* or when it gets an IO error reading an indirect block
* (ditto, *@err == -EIO)
- * or when it notices that chain had been changed while it was reading
- * (ditto, *@err == -EAGAIN)
* or when it reads all @depth-1 indirect blocks successfully and finds
* the whole chain, all way to the data (returns %NULL, *err == 0).
+ *
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex)
*/
static Indirect *ext4_get_branch(struct inode *inode, int depth,
ext4_lblk_t *offsets,
@@ -370,9 +364,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth,
bh = sb_bread(sb, le32_to_cpu(p->key));
if (!bh)
goto failure;
- /* Reader: pointers */
- if (!verify_chain(chain, p))
- goto changed;
add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
/* Reader: end */
if (!p->key)
@@ -380,10 +371,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth,
}
return NULL;

-changed:
- brelse(bh);
- *err = -EAGAIN;
- goto no_block;
failure:
*err = -EIO;
no_block:
@@ -787,6 +774,10 @@ err_out:
* return > 0, # of blocks mapped or allocated.
* return = 0, if plain lookup failed.
* return < 0, error case.
+ *
+ *
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex)
*/
int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
ext4_lblk_t iblock, unsigned long maxblocks,
@@ -825,18 +816,6 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
while (count < maxblocks && count <= blocks_to_boundary) {
ext4_fsblk_t blk;

- if (!verify_chain(chain, partial)) {
- /*
- * Indirect block might be removed by
- * truncate while we were reading it.
- * Handling of that case: forget what we've
- * got now. Flag the err as EAGAIN, so it
- * will reread.
- */
- err = -EAGAIN;
- count = 0;
- break;
- }
blk = le32_to_cpu(*(chain[depth-1].p + count));

if (blk == first_block + count)
@@ -844,44 +823,13 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
else
break;
}
- if (err != -EAGAIN)
- goto got_it;
+ goto got_it;
}

/* Next simple case - plain lookup or failed read of indirect block */
if (!create || err == -EIO)
goto cleanup;

- mutex_lock(&ei->truncate_mutex);
-
- /*
- * If the indirect block is missing while we are reading
- * the chain(ext4_get_branch() returns -EAGAIN err), or
- * if the chain has been changed after we grab the semaphore,
- * (either because another process truncated this branch, or
- * another get_block allocated this branch) re-grab the chain to see if
- * the request block has been allocated or not.
- *
- * Since we already block the truncate/other get_block
- * at this point, we will have the current copy of the chain when we
- * splice the branch into the tree.
- */
- if (err == -EAGAIN || !verify_chain(chain, partial)) {
- while (partial > chain) {
- brelse(partial->bh);
- partial--;
- }
- partial = ext4_get_branch(inode, depth, offsets, chain, &err);
- if (!partial) {
- count++;
- mutex_unlock(&ei->truncate_mutex);
- if (err)
- goto cleanup;
- clear_buffer_new(bh_result);
- goto got_it;
- }
- }
-
/*
* Okay, we need to do block allocation. Lazily initialize the block
* allocation info here if necessary
@@ -923,7 +871,6 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
*/
if (!err && extend_disksize && inode->i_size > ei->i_disksize)
ei->i_disksize = inode->i_size;
- mutex_unlock(&ei->truncate_mutex);
if (err)
goto cleanup;

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 55a376e..583049c 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -1113,6 +1113,7 @@ ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
int create, int extend_disksize)
{
int retval;
+ mutex_lock(&EXT4_I(inode)->truncate_mutex);
if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
retval = ext4_ext_get_blocks(handle, inode,
(ext4_lblk_t)block, max_blocks,
@@ -1122,6 +1123,7 @@ ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
(ext4_lblk_t)block, max_blocks,
bh, create, extend_disksize);
}
+ mutex_unlock(&EXT4_I(inode)->truncate_mutex);
return retval;
}

--
1.5.4.rc3.31.g1271-dirty


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