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Date: Sun, 01 Jun 2008 16:35:55 -0700
From: Mingming Cao <cmm@...ibm.com>
To: linux-ext4@...r.kernel.org
Subject: [RFC][PATCH 3/6] delalloc ENOSPC: reserve blocks
ext4: delalloc ENOSPC handling core
From: Mingming cao <cmm@...ibm.com>
Core part of delaloc ENOSPC (block reservation.)
data/meta blocks are reserved on write_begin(), and per-inode reserved counters
are updated after block allocation.
Signed-off-by: Mingming cao <cmm@...ibm.com>
---
fs/ext4/inode.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 66 insertions(+), 3 deletions(-)
Index: linux-2.6.26-rc4/fs/ext4/inode.c
===================================================================
--- linux-2.6.26-rc4.orig/fs/ext4/inode.c 2008-06-01 14:26:13.000000000 -0700
+++ linux-2.6.26-rc4/fs/ext4/inode.c 2008-06-01 15:04:06.000000000 -0700
@@ -38,6 +38,7 @@
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"
+#include "ext4_extents.h"
static void ext4_invalidatepage(struct page *page, unsigned long offset);
@@ -1410,6 +1411,61 @@ static int ext4_journalled_write_end(str
return ret ? ret : copied;
}
+static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ unsigned long md_needed, mdblocks, total = 0;
+
+ /*
+ * calculate the amount of metadata blocks to reserve
+ * in order to allocate nrblocks
+ * worse case is one extent per block
+ */
+ total = EXT4_I(inode)->i_reserved_data_blocks + nrblocks;
+ mdblocks = ext4_ext_calc_metadata_amount(inode, total);
+ BUG_ON(mdblocks < EXT4_I(inode)->i_reserved_meta_blocks);
+
+ md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
+ total = md_needed + nrblocks;
+
+ if (ext4_has_free_blocks(sbi, total) < total)
+ return -ENOSPC;
+
+ /* reduce fs free blocks counter */
+ percpu_counter_sub(&sbi->s_freeblocks_counter, total);
+
+ EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
+ EXT4_I(inode)->i_reserved_meta_blocks += md_needed;
+
+ return 0; /* success */
+}
+
+static void ext4_da_release_space(struct inode *inode, int used, int to_free)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ int total, mdb, release;
+
+ /* calculate the number of metablocks still need to be reserved */
+ total = EXT4_I(inode)->i_reserved_data_blocks - used - to_free;
+ mdb = ext4_ext_calc_metadata_amount(inode, total);
+
+ /* figure out how many metablocks to release */
+ BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
+ mdb = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
+
+ release = to_free + mdb;
+
+ /* update fs free blocks counter for truncate case */
+ percpu_counter_add(&sbi->s_freeblocks_counter, release);
+
+ /* update per-inode reservations */
+ BUG_ON(used + to_free > EXT4_I(inode)->i_reserved_data_blocks);
+ EXT4_I(inode)->i_reserved_data_blocks -= used + to_free;
+
+ BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
+ EXT4_I(inode)->i_reserved_meta_blocks -= mdb;
+}
+
/*
* this is a special callback for ->write_begin() only
* it's intention is to return mapped block or reserve space
@@ -1428,13 +1484,17 @@ static int ext4_da_get_block_prep(struct
* the same as allocated blocks.
*/
ret = ext4_get_blocks_wrap(NULL, inode, iblock, 1, bh_result, 0, 0);
- if (ret == 0) {
- /* the block isn't allocated yet, let's reserve space */
- /* XXX: call reservation here */
+ if ((ret == 0)&& !buffer_delay(bh_result)) {
+ /* the block isn't (pre)allocated yet, let's reserve space */
/*
* XXX: __block_prepare_write() unmaps passed block,
* is it OK?
*/
+ ret = ext4_da_reserve_space(inode, 1);
+ if (ret)
+ /* not enough space to reserve */
+ return ret;
+
map_bh(bh_result, inode->i_sb, 0);
set_buffer_new(bh_result);
set_buffer_delay(bh_result);
@@ -1463,6 +1523,9 @@ static int ext4_da_get_block_write(struc
if (ret > 0) {
bh_result->b_size = (ret << inode->i_blkbits);
+ /* release reserved-but-unused meta blocks */
+ ext4_da_release_space(inode, ret, 0);
+
/*
* Update on-disk size along with block allocation
* we don't use 'extend_disksize' as size may change
--
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