ext4: Add new abstraction ext4_map_blocks() underneath ext4_get_blocks()
Jack up ext4_get_blocks() and add a new function, ext4_map_blocks()
which uses a much smaller structure, struct ext4_map_blocks which is
20 bytes, as opposed to a struct buffer_head, which nearly 5 times
bigger on an x86_64 machine. By switching things to use
ext4_map_blocks(), we can save stack space by using ext4_map_blocks()
since we can avoid allocating a struct buffer_head on the stack.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 830336d..ff2f5fd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -149,7 +149,7 @@
int ret;
/*
- * Drop i_data_sem to avoid deadlock with ext4_get_blocks At this
+ * Drop i_data_sem to avoid deadlock with ext4_map_blocks. At this
* moment, get_block can be called only for blocks inside i_size since
* page cache has been already dropped and writes are blocked by
* i_mutex. So we can safely drop the i_data_sem here.
@@ -890,9 +890,9 @@
}
/*
- * The ext4_ind_get_blocks() function handles non-extents inodes
+ * The ext4_ind_map_blocks() function handles non-extents inodes
* (i.e., using the traditional indirect/double-indirect i_blocks
- * scheme) for ext4_get_blocks().
+ * scheme) for ext4_map_blocks().
*
* Allocation strategy is simple: if we have to allocate something, we will
* have to go the whole way to leaf. So let's do it before attaching anything
@@ -917,9 +917,8 @@
* down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
* blocks.
*/
-static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
- ext4_lblk_t iblock, unsigned int maxblocks,
- struct buffer_head *bh_result,
+static int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
+ struct ext4_map_blocks *map,
int flags)
{
int err = -EIO;
@@ -935,7 +934,7 @@
J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
- depth = ext4_block_to_path(inode, iblock, offsets,
+ depth = ext4_block_to_path(inode, map->m_lblk, offsets,
&blocks_to_boundary);
if (depth == 0)
@@ -946,10 +945,9 @@
/* Simplest case - block found, no allocation needed */
if (!partial) {
first_block = le32_to_cpu(chain[depth - 1].key);
- clear_buffer_new(bh_result);
count++;
/*map more blocks*/
- while (count < maxblocks && count <= blocks_to_boundary) {
+ while (count < map->m_len && count <= blocks_to_boundary) {
ext4_fsblk_t blk;
blk = le32_to_cpu(*(chain[depth-1].p + count));
@@ -969,7 +967,7 @@
/*
* Okay, we need to do block allocation.
*/
- goal = ext4_find_goal(inode, iblock, partial);
+ goal = ext4_find_goal(inode, map->m_lblk, partial);
/* the number of blocks need to allocate for [d,t]indirect blocks */
indirect_blks = (chain + depth) - partial - 1;
@@ -979,11 +977,11 @@
* direct blocks to allocate for this branch.
*/
count = ext4_blks_to_allocate(partial, indirect_blks,
- maxblocks, blocks_to_boundary);
+ map->m_len, blocks_to_boundary);
/*
* Block out ext4_truncate while we alter the tree
*/
- err = ext4_alloc_branch(handle, inode, iblock, indirect_blks,
+ err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
&count, goal,
offsets + (partial - chain), partial);
@@ -995,18 +993,20 @@
* may need to return -EAGAIN upwards in the worst case. --sct
*/
if (!err)
- err = ext4_splice_branch(handle, inode, iblock,
+ err = ext4_splice_branch(handle, inode, map->m_lblk,
partial, indirect_blks, count);
if (err)
goto cleanup;
- set_buffer_new(bh_result);
+ map->m_flags |= EXT4_MAP_NEW;
ext4_update_inode_fsync_trans(handle, inode, 1);
got_it:
- map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
+ map->m_flags |= EXT4_MAP_MAPPED;
+ map->m_pblk = le32_to_cpu(chain[depth-1].key);
+ map->m_len = count;
if (count > blocks_to_boundary)
- set_buffer_boundary(bh_result);
+ map->m_flags |= EXT4_MAP_BOUNDARY;
err = count;
/* Clean up and exit */
partial = chain + depth - 1; /* the whole chain */
@@ -1016,7 +1016,6 @@
brelse(partial->bh);
partial--;
}
- BUFFER_TRACE(bh_result, "returned");
out:
return err;
}
@@ -1203,15 +1202,15 @@
}
/*
- * The ext4_get_blocks() function tries to look up the requested blocks,
+ * The ext4_map_blocks() function tries to look up the requested blocks,
* and returns if the blocks are already mapped.
*
* Otherwise it takes the write lock of the i_data_sem and allocate blocks
* and store the allocated blocks in the result buffer head and mark it
* mapped.
*
- * If file type is extents based, it will call ext4_ext_get_blocks(),
- * Otherwise, call with ext4_ind_get_blocks() to handle indirect mapping
+ * If file type is extents based, it will call ext4_ext_map_blocks(),
+ * Otherwise, call with ext4_ind_map_blocks() to handle indirect mapping
* based files
*
* On success, it returns the number of blocks being mapped or allocate.
@@ -1224,35 +1223,30 @@
*
* It returns the error in case of allocation failure.
*/
-int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
- unsigned int max_blocks, struct buffer_head *bh,
- int flags)
+int ext4_map_blocks(handle_t *handle, struct inode *inode,
+ struct ext4_map_blocks *map, int flags)
{
int retval;
- clear_buffer_mapped(bh);
- clear_buffer_unwritten(bh);
-
- ext_debug("ext4_get_blocks(): inode %lu, flag %d, max_blocks %u,"
- "logical block %lu\n", inode->i_ino, flags, max_blocks,
- (unsigned long)block);
+ map->m_flags = 0;
+ ext_debug("ext4_map_blocks(): inode %lu, flag %d, max_blocks %u,"
+ "logical block %lu\n", inode->i_ino, flags, map->m_len,
+ (unsigned long) map->m_lblk);
/*
* Try to see if we can get the block without requesting a new
* file system block.
*/
down_read((&EXT4_I(inode)->i_data_sem));
if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
- retval = ext4_ext_get_blocks(handle, inode, block, max_blocks,
- bh, 0);
+ retval = ext4_ext_map_blocks(handle, inode, map, 0);
} else {
- retval = ext4_ind_get_blocks(handle, inode, block, max_blocks,
- bh, 0);
+ retval = ext4_ind_map_blocks(handle, inode, map, 0);
}
up_read((&EXT4_I(inode)->i_data_sem));
- if (retval > 0 && buffer_mapped(bh)) {
+ if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
int ret = check_block_validity(inode, "file system corruption",
- block, bh->b_blocknr, retval);
+ map->m_lblk, map->m_pblk, retval);
if (ret != 0)
return ret;
}
@@ -1268,7 +1262,7 @@
* ext4_ext_get_block() returns th create = 0
* with buffer head unmapped.
*/
- if (retval > 0 && buffer_mapped(bh))
+ if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)
return retval;
/*
@@ -1281,7 +1275,7 @@
* of BH_Unwritten and BH_Mapped flags being simultaneously
* set on the buffer_head.
*/
- clear_buffer_unwritten(bh);
+ map->m_flags &= ~EXT4_MAP_UNWRITTEN;
/*
* New blocks allocate and/or writing to uninitialized extent
@@ -1304,13 +1298,11 @@
* could have changed the inode type in between
*/
if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
- retval = ext4_ext_get_blocks(handle, inode, block, max_blocks,
- bh, flags);
+ retval = ext4_ext_map_blocks(handle, inode, map, flags);
} else {
- retval = ext4_ind_get_blocks(handle, inode, block,
- max_blocks, bh, flags);
+ retval = ext4_ind_map_blocks(handle, inode, map, flags);
- if (retval > 0 && buffer_new(bh)) {
+ if (retval > 0 && map->m_flags & EXT4_MAP_NEW) {
/*
* We allocated new blocks which will result in
* i_data's format changing. Force the migrate
@@ -1333,16 +1325,38 @@
EXT4_I(inode)->i_delalloc_reserved_flag = 0;
up_write((&EXT4_I(inode)->i_data_sem));
- if (retval > 0 && buffer_mapped(bh)) {
+ if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
int ret = check_block_validity(inode, "file system "
"corruption after allocation",
- block, bh->b_blocknr, retval);
+ map->m_lblk, map->m_pblk,
+ retval);
if (ret != 0)
return ret;
}
return retval;
}
+int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
+ unsigned int max_blocks, struct buffer_head *bh,
+ int flags)
+{
+ struct ext4_map_blocks map;
+ int ret;
+
+ map.m_lblk = block;
+ map.m_len = max_blocks;
+
+ ret = ext4_map_blocks(handle, inode, &map, flags);
+ if (ret < 0)
+ return ret;
+
+ bh->b_blocknr = map.m_pblk;
+ bh->b_size = inode->i_sb->s_blocksize * map.m_len;
+ bh->b_bdev = inode->i_sb->s_bdev;
+ bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+ return ret;
+}
+
/* Maximum number of blocks we map for direct IO at once. */
#define DIO_MAX_BLOCKS 4096