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balloc.c
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/*
* linux/fs/ext3/balloc.c
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card ([email protected])
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* Enhanced block allocation by Stephen Tweedie ([email protected]), 1993
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller ([email protected]), 1995
*/
#include <linux/time.h>
#include <linux/capability.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/jbd.h>
#include <linux/ext3_fs.h>
#include <linux/ext3_jbd.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
/*
* balloc.c contains the blocks allocation and deallocation routines
*/
/*
* The free blocks are managed by bitmaps. A file system contains several
* blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap
* block for inodes, N blocks for the inode table and data blocks.
*
* The file system contains group descriptors which are located after the
* super block. Each descriptor contains the number of the bitmap block and
* the free blocks count in the block. The descriptors are loaded in memory
* when a file system is mounted (see ext3_fill_super).
*/
#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
/*
* Calculate the block group number and offset, given a block number
*/
static void ext3_get_group_no_and_offset(struct super_block *sb,
ext3_fsblk_t blocknr, unsigned long *blockgrpp, ext3_grpblk_t *offsetp)
{
struct ext3_super_block *es = EXT3_SB(sb)->s_es;
blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
if (offsetp)
*offsetp = blocknr % EXT3_BLOCKS_PER_GROUP(sb);
if (blockgrpp)
*blockgrpp = blocknr / EXT3_BLOCKS_PER_GROUP(sb);
}
/**
* ext3_get_group_desc() -- load group descriptor from disk
* @sb: super block
* @block_group: given block group
* @bh: pointer to the buffer head to store the block
* group descriptor
*/
struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
unsigned int block_group,
struct buffer_head ** bh)
{
unsigned long group_desc;
unsigned long offset;
struct ext3_group_desc * desc;
struct ext3_sb_info *sbi = EXT3_SB(sb);
if (block_group >= sbi->s_groups_count) {
ext3_error (sb, "ext3_get_group_desc",
"block_group >= groups_count - "
"block_group = %d, groups_count = %lu",
block_group, sbi->s_groups_count);
return NULL;
}
smp_rmb();
group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(sb);
offset = block_group & (EXT3_DESC_PER_BLOCK(sb) - 1);
if (!sbi->s_group_desc[group_desc]) {
ext3_error (sb, "ext3_get_group_desc",
"Group descriptor not loaded - "
"block_group = %d, group_desc = %lu, desc = %lu",
block_group, group_desc, offset);
return NULL;
}
desc = (struct ext3_group_desc *) sbi->s_group_desc[group_desc]->b_data;
if (bh)
*bh = sbi->s_group_desc[group_desc];
return desc + offset;
}
static int ext3_valid_block_bitmap(struct super_block *sb,
struct ext3_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
{
ext3_grpblk_t offset;
ext3_grpblk_t next_zero_bit;
ext3_fsblk_t bitmap_blk;
ext3_fsblk_t group_first_block;
group_first_block = ext3_group_first_block_no(sb, block_group);
/* check whether block bitmap block number is set */
bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
offset = bitmap_blk - group_first_block;
if (!ext3_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode bitmap block number is set */
bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
offset = bitmap_blk - group_first_block;
if (!ext3_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode table block number is set */
bitmap_blk = le32_to_cpu(desc->bg_inode_table);
offset = bitmap_blk - group_first_block;
next_zero_bit = ext3_find_next_zero_bit(bh->b_data,
offset + EXT3_SB(sb)->s_itb_per_group,
offset);
if (next_zero_bit >= offset + EXT3_SB(sb)->s_itb_per_group)
/* good bitmap for inode tables */
return 1;
err_out:
ext3_error(sb, __func__,
"Invalid block bitmap - "
"block_group = %d, block = %lu",
block_group, bitmap_blk);
return 0;
}
/**
* read_block_bitmap()
* @sb: super block
* @block_group: given block group
*
* Read the bitmap for a given block_group,and validate the
* bits for block/inode/inode tables are set in the bitmaps
*
* Return buffer_head on success or NULL in case of failure.
*/
static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
struct ext3_group_desc * desc;
struct buffer_head * bh = NULL;
ext3_fsblk_t bitmap_blk;
desc = ext3_get_group_desc(sb, block_group, NULL);
if (!desc)
return NULL;
bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
bh = sb_getblk(sb, bitmap_blk);
if (unlikely(!bh)) {
ext3_error(sb, __func__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %u",
block_group, le32_to_cpu(desc->bg_block_bitmap));
return NULL;
}
if (likely(bh_uptodate_or_lock(bh)))
return bh;
if (bh_submit_read(bh) < 0) {
brelse(bh);
ext3_error(sb, __func__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %u",
block_group, le32_to_cpu(desc->bg_block_bitmap));
return NULL;
}
ext3_valid_block_bitmap(sb, desc, block_group, bh);
/*
* file system mounted not to panic on error, continue with corrupt
* bitmap
*/
return bh;
}
/*
* The reservation window structure operations
* --------------------------------------------
* Operations include:
* dump, find, add, remove, is_empty, find_next_reservable_window, etc.
*
* We use a red-black tree to represent per-filesystem reservation
* windows.
*
*/
/**
* __rsv_window_dump() -- Dump the filesystem block allocation reservation map
* @rb_root: root of per-filesystem reservation rb tree
* @verbose: verbose mode
* @fn: function which wishes to dump the reservation map
*
* If verbose is turned on, it will print the whole block reservation
* windows(start, end). Otherwise, it will only print out the "bad" windows,
* those windows that overlap with their immediate neighbors.
*/
#if 1
static void __rsv_window_dump(struct rb_root *root, int verbose,
const char *fn)
{
struct rb_node *n;
struct ext3_reserve_window_node *rsv, *prev;
int bad;
restart:
n = rb_first(root);
bad = 0;
prev = NULL;
printk("Block Allocation Reservation Windows Map (%s):\n", fn);
while (n) {
rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
if (verbose)
printk("reservation window 0x%p "
"start: %lu, end: %lu\n",
rsv, rsv->rsv_start, rsv->rsv_end);
if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
printk("Bad reservation %p (start >= end)\n",
rsv);
bad = 1;
}
if (prev && prev->rsv_end >= rsv->rsv_start) {
printk("Bad reservation %p (prev->end >= start)\n",
rsv);
bad = 1;
}
if (bad) {
if (!verbose) {
printk("Restarting reservation walk in verbose mode\n");
verbose = 1;
goto restart;
}
}
n = rb_next(n);
prev = rsv;
}
printk("Window map complete.\n");
BUG_ON(bad);
}
#define rsv_window_dump(root, verbose) \
__rsv_window_dump((root), (verbose), __func__)
#else
#define rsv_window_dump(root, verbose) do {} while (0)
#endif
/**
* goal_in_my_reservation()
* @rsv: inode's reservation window
* @grp_goal: given goal block relative to the allocation block group
* @group: the current allocation block group
* @sb: filesystem super block
*
* Test if the given goal block (group relative) is within the file's
* own block reservation window range.
*
* If the reservation window is outside the goal allocation group, return 0;
* grp_goal (given goal block) could be -1, which means no specific
* goal block. In this case, always return 1.
* If the goal block is within the reservation window, return 1;
* otherwise, return 0;
*/
static int
goal_in_my_reservation(struct ext3_reserve_window *rsv, ext3_grpblk_t grp_goal,
unsigned int group, struct super_block * sb)
{
ext3_fsblk_t group_first_block, group_last_block;
group_first_block = ext3_group_first_block_no(sb, group);
group_last_block = group_first_block + (EXT3_BLOCKS_PER_GROUP(sb) - 1);
if ((rsv->_rsv_start > group_last_block) ||
(rsv->_rsv_end < group_first_block))
return 0;
if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
|| (grp_goal + group_first_block > rsv->_rsv_end)))
return 0;
return 1;
}
/**
* search_reserve_window()
* @rb_root: root of reservation tree
* @goal: target allocation block
*
* Find the reserved window which includes the goal, or the previous one
* if the goal is not in any window.
* Returns NULL if there are no windows or if all windows start after the goal.
*/
static struct ext3_reserve_window_node *
search_reserve_window(struct rb_root *root, ext3_fsblk_t goal)
{
struct rb_node *n = root->rb_node;
struct ext3_reserve_window_node *rsv;
if (!n)
return NULL;
do {
rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
if (goal < rsv->rsv_start)
n = n->rb_left;
else if (goal > rsv->rsv_end)
n = n->rb_right;
else
return rsv;
} while (n);
/*
* We've fallen off the end of the tree: the goal wasn't inside
* any particular node. OK, the previous node must be to one
* side of the interval containing the goal. If it's the RHS,
* we need to back up one.
*/
if (rsv->rsv_start > goal) {
n = rb_prev(&rsv->rsv_node);
rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
}
return rsv;
}
/**
* ext3_rsv_window_add() -- Insert a window to the block reservation rb tree.
* @sb: super block
* @rsv: reservation window to add
*
* Must be called with rsv_lock hold.
*/
void ext3_rsv_window_add(struct super_block *sb,
struct ext3_reserve_window_node *rsv)
{
struct rb_root *root = &EXT3_SB(sb)->s_rsv_window_root;
struct rb_node *node = &rsv->rsv_node;
ext3_fsblk_t start = rsv->rsv_start;
struct rb_node ** p = &root->rb_node;
struct rb_node * parent = NULL;
struct ext3_reserve_window_node *this;
while (*p)
{
parent = *p;
this = rb_entry(parent, struct ext3_reserve_window_node, rsv_node);
if (start < this->rsv_start)
p = &(*p)->rb_left;
else if (start > this->rsv_end)
p = &(*p)->rb_right;
else {
rsv_window_dump(root, 1);
BUG();
}
}
rb_link_node(node, parent, p);
rb_insert_color(node, root);
}
/**
* ext3_rsv_window_remove() -- unlink a window from the reservation rb tree
* @sb: super block
* @rsv: reservation window to remove
*
* Mark the block reservation window as not allocated, and unlink it
* from the filesystem reservation window rb tree. Must be called with
* rsv_lock hold.
*/
static void rsv_window_remove(struct super_block *sb,
struct ext3_reserve_window_node *rsv)
{
rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_alloc_hit = 0;
rb_erase(&rsv->rsv_node, &EXT3_SB(sb)->s_rsv_window_root);
}
/*
* rsv_is_empty() -- Check if the reservation window is allocated.
* @rsv: given reservation window to check
*
* returns 1 if the end block is EXT3_RESERVE_WINDOW_NOT_ALLOCATED.
*/
static inline int rsv_is_empty(struct ext3_reserve_window *rsv)
{
/* a valid reservation end block could not be 0 */
return rsv->_rsv_end == EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
}
/**
* ext3_init_block_alloc_info()
* @inode: file inode structure
*
* Allocate and initialize the reservation window structure, and
* link the window to the ext3 inode structure at last
*
* The reservation window structure is only dynamically allocated
* and linked to ext3 inode the first time the open file
* needs a new block. So, before every ext3_new_block(s) call, for
* regular files, we should check whether the reservation window
* structure exists or not. In the latter case, this function is called.
* Fail to do so will result in block reservation being turned off for that
* open file.
*
* This function is called from ext3_get_blocks_handle(), also called
* when setting the reservation window size through ioctl before the file
* is open for write (needs block allocation).
*
* Needs truncate_mutex protection prior to call this function.
*/
void ext3_init_block_alloc_info(struct inode *inode)
{
struct ext3_inode_info *ei = EXT3_I(inode);
struct ext3_block_alloc_info *block_i = ei->i_block_alloc_info;
struct super_block *sb = inode->i_sb;
block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
if (block_i) {
struct ext3_reserve_window_node *rsv = &block_i->rsv_window_node;
rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
/*
* if filesystem is mounted with NORESERVATION, the goal
* reservation window size is set to zero to indicate
* block reservation is off
*/
if (!test_opt(sb, RESERVATION))
rsv->rsv_goal_size = 0;
else
rsv->rsv_goal_size = EXT3_DEFAULT_RESERVE_BLOCKS;
rsv->rsv_alloc_hit = 0;
block_i->last_alloc_logical_block = 0;
block_i->last_alloc_physical_block = 0;
}
ei->i_block_alloc_info = block_i;
}
/**
* ext3_discard_reservation()
* @inode: inode
*
* Discard(free) block reservation window on last file close, or truncate
* or at last iput().
*
* It is being called in three cases:
* ext3_release_file(): last writer close the file
* ext3_clear_inode(): last iput(), when nobody link to this file.
* ext3_truncate(): when the block indirect map is about to change.
*
*/
void ext3_discard_reservation(struct inode *inode)
{
struct ext3_inode_info *ei = EXT3_I(inode);
struct ext3_block_alloc_info *block_i = ei->i_block_alloc_info;
struct ext3_reserve_window_node *rsv;
spinlock_t *rsv_lock = &EXT3_SB(inode->i_sb)->s_rsv_window_lock;
if (!block_i)
return;
rsv = &block_i->rsv_window_node;
if (!rsv_is_empty(&rsv->rsv_window)) {
spin_lock(rsv_lock);
if (!rsv_is_empty(&rsv->rsv_window))
rsv_window_remove(inode->i_sb, rsv);
spin_unlock(rsv_lock);
}
}
/**
* ext3_free_blocks_sb() -- Free given blocks and update quota
* @handle: handle to this transaction
* @sb: super block
* @block: start physcial block to free
* @count: number of blocks to free
* @pdquot_freed_blocks: pointer to quota
*/
void ext3_free_blocks_sb(handle_t *handle, struct super_block *sb,
ext3_fsblk_t block, unsigned long count,
unsigned long *pdquot_freed_blocks)
{
struct buffer_head *bitmap_bh = NULL;
struct buffer_head *gd_bh;
unsigned long block_group;
ext3_grpblk_t bit;
unsigned long i;
unsigned long overflow;
struct ext3_group_desc * desc;
struct ext3_super_block * es;
struct ext3_sb_info *sbi;
int err = 0, ret;
ext3_grpblk_t group_freed;
*pdquot_freed_blocks = 0;
sbi = EXT3_SB(sb);
es = sbi->s_es;
if (block < le32_to_cpu(es->s_first_data_block) ||
block + count < block ||
block + count > le32_to_cpu(es->s_blocks_count)) {
ext3_error (sb, "ext3_free_blocks",
"Freeing blocks not in datazone - "
"block = "E3FSBLK", count = %lu", block, count);
goto error_return;
}
ext3_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);
do_more:
overflow = 0;
block_group = (block - le32_to_cpu(es->s_first_data_block)) /
EXT3_BLOCKS_PER_GROUP(sb);
bit = (block - le32_to_cpu(es->s_first_data_block)) %
EXT3_BLOCKS_PER_GROUP(sb);
/*
* Check to see if we are freeing blocks across a group
* boundary.
*/
if (bit + count > EXT3_BLOCKS_PER_GROUP(sb)) {
overflow = bit + count - EXT3_BLOCKS_PER_GROUP(sb);
count -= overflow;
}
brelse(bitmap_bh);
bitmap_bh = read_block_bitmap(sb, block_group);
if (!bitmap_bh)
goto error_return;
desc = ext3_get_group_desc (sb, block_group, &gd_bh);
if (!desc)
goto error_return;
if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
in_range (block, le32_to_cpu(desc->bg_inode_table),
sbi->s_itb_per_group) ||
in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
sbi->s_itb_per_group)) {
ext3_error (sb, "ext3_free_blocks",
"Freeing blocks in system zones - "
"Block = "E3FSBLK", count = %lu",
block, count);
goto error_return;
}
/*
* We are about to start releasing blocks in the bitmap,
* so we need undo access.
*/
/* @@@ check errors */
BUFFER_TRACE(bitmap_bh, "getting undo access");
err = ext3_journal_get_undo_access(handle, bitmap_bh);
if (err)
goto error_return;
/*
* We are about to modify some metadata. Call the journal APIs
* to unshare ->b_data if a currently-committing transaction is
* using it
*/
BUFFER_TRACE(gd_bh, "get_write_access");
err = ext3_journal_get_write_access(handle, gd_bh);
if (err)
goto error_return;
jbd_lock_bh_state(bitmap_bh);
for (i = 0, group_freed = 0; i < count; i++) {
/*
* An HJ special. This is expensive...
*/
#ifdef CONFIG_JBD_DEBUG
jbd_unlock_bh_state(bitmap_bh);
{
struct buffer_head *debug_bh;
debug_bh = sb_find_get_block(sb, block + i);
if (debug_bh) {
BUFFER_TRACE(debug_bh, "Deleted!");
if (!bh2jh(bitmap_bh)->b_committed_data)
BUFFER_TRACE(debug_bh,
"No committed data in bitmap");
BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
__brelse(debug_bh);
}
}
jbd_lock_bh_state(bitmap_bh);
#endif
if (need_resched()) {
jbd_unlock_bh_state(bitmap_bh);
cond_resched();
jbd_lock_bh_state(bitmap_bh);
}
/* @@@ This prevents newly-allocated data from being
* freed and then reallocated within the same
* transaction.
*
* Ideally we would want to allow that to happen, but to
* do so requires making journal_forget() capable of
* revoking the queued write of a data block, which
* implies blocking on the journal lock. *forget()
* cannot block due to truncate races.
*
* Eventually we can fix this by making journal_forget()
* return a status indicating whether or not it was able
* to revoke the buffer. On successful revoke, it is
* safe not to set the allocation bit in the committed
* bitmap, because we know that there is no outstanding
* activity on the buffer any more and so it is safe to
* reallocate it.
*/
BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
J_ASSERT_BH(bitmap_bh,
bh2jh(bitmap_bh)->b_committed_data != NULL);
ext3_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
bh2jh(bitmap_bh)->b_committed_data);
/*
* We clear the bit in the bitmap after setting the committed
* data bit, because this is the reverse order to that which
* the allocator uses.
*/
BUFFER_TRACE(bitmap_bh, "clear bit");
if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
bit + i, bitmap_bh->b_data)) {
jbd_unlock_bh_state(bitmap_bh);
ext3_error(sb, __func__,
"bit already cleared for block "E3FSBLK,
block + i);
jbd_lock_bh_state(bitmap_bh);
BUFFER_TRACE(bitmap_bh, "bit already cleared");
} else {
group_freed++;
}
}
jbd_unlock_bh_state(bitmap_bh);
spin_lock(sb_bgl_lock(sbi, block_group));
le16_add_cpu(&desc->bg_free_blocks_count, group_freed);
spin_unlock(sb_bgl_lock(sbi, block_group));
percpu_counter_add(&sbi->s_freeblocks_counter, count);
/* We dirtied the bitmap block */
BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
err = ext3_journal_dirty_metadata(handle, bitmap_bh);
/* And the group descriptor block */
BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
ret = ext3_journal_dirty_metadata(handle, gd_bh);
if (!err) err = ret;
*pdquot_freed_blocks += group_freed;
if (overflow && !err) {
block += count;
count = overflow;
goto do_more;
}
error_return:
brelse(bitmap_bh);
ext3_std_error(sb, err);
return;
}
/**
* ext3_free_blocks() -- Free given blocks and update quota
* @handle: handle for this transaction
* @inode: inode
* @block: start physical block to free
* @count: number of blocks to count
*/
void ext3_free_blocks(handle_t *handle, struct inode *inode,
ext3_fsblk_t block, unsigned long count)
{
struct super_block * sb;
unsigned long dquot_freed_blocks;
sb = inode->i_sb;
if (!sb) {
printk ("ext3_free_blocks: nonexistent device");
return;
}
ext3_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
if (dquot_freed_blocks)
dquot_free_block(inode, dquot_freed_blocks);
return;
}
/**
* ext3_test_allocatable()
* @nr: given allocation block group
* @bh: bufferhead contains the bitmap of the given block group
*
* For ext3 allocations, we must not reuse any blocks which are
* allocated in the bitmap buffer's "last committed data" copy. This
* prevents deletes from freeing up the page for reuse until we have
* committed the delete transaction.
*
* If we didn't do this, then deleting something and reallocating it as
* data would allow the old block to be overwritten before the
* transaction committed (because we force data to disk before commit).
* This would lead to corruption if we crashed between overwriting the
* data and committing the delete.
*
* @@@ We may want to make this allocation behaviour conditional on
* data-writes at some point, and disable it for metadata allocations or
* sync-data inodes.
*/
static int ext3_test_allocatable(ext3_grpblk_t nr, struct buffer_head *bh)
{
int ret;
struct journal_head *jh = bh2jh(bh);
if (ext3_test_bit(nr, bh->b_data))
return 0;
jbd_lock_bh_state(bh);
if (!jh->b_committed_data)
ret = 1;
else
ret = !ext3_test_bit(nr, jh->b_committed_data);
jbd_unlock_bh_state(bh);
return ret;
}
/**
* bitmap_search_next_usable_block()
* @start: the starting block (group relative) of the search
* @bh: bufferhead contains the block group bitmap
* @maxblocks: the ending block (group relative) of the reservation
*
* The bitmap search --- search forward alternately through the actual
* bitmap on disk and the last-committed copy in journal, until we find a
* bit free in both bitmaps.
*/
static ext3_grpblk_t
bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
ext3_grpblk_t maxblocks)
{
ext3_grpblk_t next;
struct journal_head *jh = bh2jh(bh);
while (start < maxblocks) {
next = ext3_find_next_zero_bit(bh->b_data, maxblocks, start);
if (next >= maxblocks)
return -1;
if (ext3_test_allocatable(next, bh))
return next;
jbd_lock_bh_state(bh);
if (jh->b_committed_data)
start = ext3_find_next_zero_bit(jh->b_committed_data,
maxblocks, next);
jbd_unlock_bh_state(bh);
}
return -1;
}
/**
* find_next_usable_block()
* @start: the starting block (group relative) to find next
* allocatable block in bitmap.
* @bh: bufferhead contains the block group bitmap
* @maxblocks: the ending block (group relative) for the search
*
* Find an allocatable block in a bitmap. We honor both the bitmap and
* its last-committed copy (if that exists), and perform the "most
* appropriate allocation" algorithm of looking for a free block near
* the initial goal; then for a free byte somewhere in the bitmap; then
* for any free bit in the bitmap.
*/
static ext3_grpblk_t
find_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
ext3_grpblk_t maxblocks)
{
ext3_grpblk_t here, next;
char *p, *r;
if (start > 0) {
/*
* The goal was occupied; search forward for a free
* block within the next XX blocks.
*
* end_goal is more or less random, but it has to be
* less than EXT3_BLOCKS_PER_GROUP. Aligning up to the
* next 64-bit boundary is simple..
*/
ext3_grpblk_t end_goal = (start + 63) & ~63;
if (end_goal > maxblocks)
end_goal = maxblocks;
here = ext3_find_next_zero_bit(bh->b_data, end_goal, start);
if (here < end_goal && ext3_test_allocatable(here, bh))
return here;
ext3_debug("Bit not found near goal\n");
}
here = start;
if (here < 0)
here = 0;
p = bh->b_data + (here >> 3);
r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
next = (r - bh->b_data) << 3;
if (next < maxblocks && next >= start && ext3_test_allocatable(next, bh))
return next;
/*
* The bitmap search --- search forward alternately through the actual
* bitmap and the last-committed copy until we find a bit free in
* both
*/
here = bitmap_search_next_usable_block(here, bh, maxblocks);
return here;
}
/**
* claim_block()
* @lock: the spin lock for this block group
* @block: the free block (group relative) to allocate
* @bh: the buffer_head contains the block group bitmap
*
* We think we can allocate this block in this bitmap. Try to set the bit.
* If that succeeds then check that nobody has allocated and then freed the
* block since we saw that is was not marked in b_committed_data. If it _was_
* allocated and freed then clear the bit in the bitmap again and return
* zero (failure).
*/
static inline int
claim_block(spinlock_t *lock, ext3_grpblk_t block, struct buffer_head *bh)
{
struct journal_head *jh = bh2jh(bh);
int ret;
if (ext3_set_bit_atomic(lock, block, bh->b_data))
return 0;
jbd_lock_bh_state(bh);
if (jh->b_committed_data && ext3_test_bit(block,jh->b_committed_data)) {
ext3_clear_bit_atomic(lock, block, bh->b_data);
ret = 0;
} else {
ret = 1;
}
jbd_unlock_bh_state(bh);
return ret;
}
/**
* ext3_try_to_allocate()
* @sb: superblock
* @handle: handle to this transaction
* @group: given allocation block group
* @bitmap_bh: bufferhead holds the block bitmap
* @grp_goal: given target block within the group
* @count: target number of blocks to allocate
* @my_rsv: reservation window
*
* Attempt to allocate blocks within a give range. Set the range of allocation
* first, then find the first free bit(s) from the bitmap (within the range),
* and at last, allocate the blocks by claiming the found free bit as allocated.
*
* To set the range of this allocation:
* if there is a reservation window, only try to allocate block(s) from the
* file's own reservation window;
* Otherwise, the allocation range starts from the give goal block, ends at
* the block group's last block.
*
* If we failed to allocate the desired block then we may end up crossing to a
* new bitmap. In that case we must release write access to the old one via
* ext3_journal_release_buffer(), else we'll run out of credits.
*/
static ext3_grpblk_t
ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
struct buffer_head *bitmap_bh, ext3_grpblk_t grp_goal,
unsigned long *count, struct ext3_reserve_window *my_rsv)
{
ext3_fsblk_t group_first_block;
ext3_grpblk_t start, end;
unsigned long num = 0;
/* we do allocation within the reservation window if we have a window */
if (my_rsv) {
group_first_block = ext3_group_first_block_no(sb, group);
if (my_rsv->_rsv_start >= group_first_block)
start = my_rsv->_rsv_start - group_first_block;
else
/* reservation window cross group boundary */
start = 0;
end = my_rsv->_rsv_end - group_first_block + 1;
if (end > EXT3_BLOCKS_PER_GROUP(sb))
/* reservation window crosses group boundary */
end = EXT3_BLOCKS_PER_GROUP(sb);
if ((start <= grp_goal) && (grp_goal < end))
start = grp_goal;
else
grp_goal = -1;
} else {
if (grp_goal > 0)
start = grp_goal;
else
start = 0;
end = EXT3_BLOCKS_PER_GROUP(sb);
}
BUG_ON(start > EXT3_BLOCKS_PER_GROUP(sb));
repeat:
if (grp_goal < 0 || !ext3_test_allocatable(grp_goal, bitmap_bh)) {
grp_goal = find_next_usable_block(start, bitmap_bh, end);
if (grp_goal < 0)
goto fail_access;
if (!my_rsv) {
int i;
for (i = 0; i < 7 && grp_goal > start &&
ext3_test_allocatable(grp_goal - 1,
bitmap_bh);
i++, grp_goal--)
;
}
}
start = grp_goal;
if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group),
grp_goal, bitmap_bh)) {
/*
* The block was allocated by another thread, or it was
* allocated and then freed by another thread
*/
start++;
grp_goal++;
if (start >= end)
goto fail_access;
goto repeat;
}
num++;
grp_goal++;
while (num < *count && grp_goal < end
&& ext3_test_allocatable(grp_goal, bitmap_bh)
&& claim_block(sb_bgl_lock(EXT3_SB(sb), group),
grp_goal, bitmap_bh)) {
num++;
grp_goal++;
}
*count = num;
return grp_goal - num;
fail_access:
*count = num;
return -1;
}
/**
* find_next_reservable_window():
* find a reservable space within the given range.
* It does not allocate the reservation window for now:
* alloc_new_reservation() will do the work later.
*
* @search_head: the head of the searching list;
* This is not necessarily the list head of the whole filesystem
*
* We have both head and start_block to assist the search
* for the reservable space. The list starts from head,
* but we will shift to the place where start_block is,
* then start from there, when looking for a reservable space.
*
* @my_rsv: the reservation window
*
* @sb: the super block
*
* @start_block: the first block we consider to start
* the real search from
*
* @last_block:
* the maximum block number that our goal reservable space
* could start from. This is normally the last block in this
* group. The search will end when we found the start of next
* possible reservable space is out of this boundary.
* This could handle the cross boundary reservation window
* request.
*
* basically we search from the given range, rather than the whole
* reservation double linked list, (start_block, last_block)
* to find a free region that is of my size and has not
* been reserved.
*
*/
static int find_next_reservable_window(
struct ext3_reserve_window_node *search_head,
struct ext3_reserve_window_node *my_rsv,
struct super_block * sb,