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Date: Thu, 28 Jun 2007 14:38:52 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: linux-ext4@...r.kernel.org
Cc: aneesh.kumar@...ux.vnet.ibm.com
Subject: [PATCH 1/2] ext4_get_blocks_wrap take the truncate_mutex early.
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().
I haven't done any performance benchmark with this change.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
fs/ext4/extents.c | 7 +++--
fs/ext4/inode.c | 69 +++++-----------------------------------------
include/linux/ext4_fs.h | 15 +++++++---
3 files changed, 23 insertions(+), 68 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index b9ce241..8193e97 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1977,6 +1977,10 @@ void ext4_ext_release(struct super_block *sb)
#endif
}
+/*
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex);
+ */
int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
ext4_fsblk_t iblock,
unsigned long max_blocks, struct buffer_head *bh_result,
@@ -1991,7 +1995,6 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
__clear_bit(BH_New, &bh_result->b_state);
ext_debug("blocks %d/%lu requested for inode %u\n", (int) iblock,
max_blocks, (unsigned) inode->i_ino);
- mutex_lock(&EXT4_I(inode)->truncate_mutex);
/* check in cache */
goal = ext4_ext_in_cache(inode, iblock, &newex);
@@ -2127,8 +2130,6 @@ out2:
ext4_ext_drop_refs(path);
kfree(path);
}
- mutex_unlock(&EXT4_I(inode)->truncate_mutex);
-
return err ? err : allocated;
}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8416fa2..255db76 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)
@@ -344,10 +337,11 @@ 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, int *offsets,
Indirect chain[4], int *err)
@@ -365,9 +359,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth, int *offsets,
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)
@@ -375,10 +366,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth, int *offsets,
}
return NULL;
-changed:
- brelse(bh);
- *err = -EAGAIN;
- goto no_block;
failure:
*err = -EIO;
no_block:
@@ -782,6 +769,10 @@ 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,
sector_t iblock, unsigned long maxblocks,
@@ -819,18 +810,6 @@ 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)
@@ -838,44 +817,13 @@ 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
@@ -917,7 +865,6 @@ 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 de1f9f7..ebd6f86 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -988,11 +988,18 @@ ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
unsigned long max_blocks, struct buffer_head *bh,
int create, int extend_disksize)
{
- if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
- return ext4_ext_get_blocks(handle, inode, block, max_blocks,
+ 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, block, max_blocks,
bh, create, extend_disksize);
- return ext4_get_blocks_handle(handle, inode, block, max_blocks, bh,
- create, extend_disksize);
+ } else {
+ retval = ext4_get_blocks_handle(handle, inode, block, max_blocks,
+ bh, create, extend_disksize);
+ }
+ mutex_unlock(&EXT4_I(inode)->truncate_mutex);
+
+ return retval;
}
--
1.5.2.2.571.ge1341-dirty
-
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