ext4: Convert callers of ext4_get_blocks() to use ext4_map_blocks()

This saves a huge amount of stack space by avoiding unnecesary struct
buffer_head's from being allocated on the stack.

In addition, to make the code easier to understand, collapse and
refactor ext4_get_block(), ext4_get_block_write(),
noalloc_get_block_write(), into a single function.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 17 insertions, 23 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 37f938789344..d6801eb7232b 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3667,13 +3667,12 @@ static void ext4_falloc_update_inode(struct inode *inode,
 long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
 {
         handle_t *handle;
-        ext4_lblk_t block;
         loff_t new_size;
         unsigned int max_blocks;
         int ret = 0;
         int ret2 = 0;
         int retries = 0;
-        struct buffer_head map_bh;
+        struct ext4_map_blocks map;
         unsigned int credits, blkbits = inode->i_blkbits;
 
         /*
@@ -3687,13 +3686,13 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
         if (S_ISDIR(inode->i_mode))
                 return -ENODEV;
 
-        block = offset >> blkbits;
+        map.m_lblk = offset >> blkbits;
         /*
          * We can't just convert len to max_blocks because
          * If blocksize = 4096 offset = 3072 and len = 2048
          */
         max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
-                                                        - block;
+                - map.m_lblk;
         /*
          * credits to insert 1 extent into extent tree
          */
@@ -3706,16 +3705,14 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
         }
 retry:
         while (ret >= 0 && ret < max_blocks) {
-                block = block + ret;
-                max_blocks = max_blocks - ret;
+                map.m_lblk = map.m_lblk + ret;
+                map.m_len = max_blocks = max_blocks - ret;
                 handle = ext4_journal_start(inode, credits);
                 if (IS_ERR(handle)) {
                         ret = PTR_ERR(handle);
                         break;
                 }
-                map_bh.b_state = 0;
-                ret = ext4_get_blocks(handle, inode, block,
-                                      max_blocks, &map_bh,
+                ret = ext4_map_blocks(handle, inode, &map,
                                       EXT4_GET_BLOCKS_CREATE_UNINIT_EXT);
                 if (ret <= 0) {
 #ifdef EXT4FS_DEBUG
@@ -3729,14 +3726,14 @@ retry:
                         ret2 = ext4_journal_stop(handle);
                         break;
                 }
-                if ((block + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
+                if ((map.m_lblk + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
                                                 blkbits) >> blkbits))
                         new_size = offset + len;
                 else
-                        new_size = (block + ret) << blkbits;
+                        new_size = (map.m_lblk + ret) << blkbits;
 
                 ext4_falloc_update_inode(inode, mode, new_size,
-                                                buffer_new(&map_bh));
+                                         (map.m_flags & EXT4_MAP_NEW));
                 ext4_mark_inode_dirty(handle, inode);
                 ret2 = ext4_journal_stop(handle);
                 if (ret2)
@@ -3765,42 +3762,39 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
                                     ssize_t len)
 {
         handle_t *handle;
-        ext4_lblk_t block;
         unsigned int max_blocks;
         int ret = 0;
         int ret2 = 0;
-        struct buffer_head map_bh;
+        struct ext4_map_blocks map;
         unsigned int credits, blkbits = inode->i_blkbits;
 
-        block = offset >> blkbits;
+        map.m_lblk = offset >> blkbits;
         /*
          * We can't just convert len to max_blocks because
          * If blocksize = 4096 offset = 3072 and len = 2048
          */
-        max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
-                                                        - block;
+        max_blocks = ((EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits) -
+                      map.m_lblk);
         /*
          * credits to insert 1 extent into extent tree
          */
         credits = ext4_chunk_trans_blocks(inode, max_blocks);
         while (ret >= 0 && ret < max_blocks) {
-                block = block + ret;
-                max_blocks = max_blocks - ret;
+                map.m_lblk += ret;
+                map.m_len = (max_blocks -= ret);
                 handle = ext4_journal_start(inode, credits);
                 if (IS_ERR(handle)) {
                         ret = PTR_ERR(handle);
                         break;
                 }
-                map_bh.b_state = 0;
-                ret = ext4_get_blocks(handle, inode, block,
-                                      max_blocks, &map_bh,
+                ret = ext4_map_blocks(handle, inode, &map,
                                       EXT4_GET_BLOCKS_IO_CONVERT_EXT);
                 if (ret <= 0) {
                         WARN_ON(ret <= 0);
                         printk(KERN_ERR "%s: ext4_ext_map_blocks "
                                     "returned error inode#%lu, block=%u, "
                                     "max_blocks=%u", __func__,
-                                    inode->i_ino, block, max_blocks);
+                                    inode->i_ino, map.m_lblk, map.m_len);
                 }
                 ext4_mark_inode_dirty(handle, inode);
                 ret2 = ext4_journal_stop(handle);