minix/servers/ext2/ialloc.c

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/* This files manages inodes allocation and deallocation.
*
* The entry points into this file are:
* alloc_inode: allocate a new, unused inode.
* free_inode: mark an inode as available for a new file.
*
* Created (alloc_inode/free_inode/wipe_inode are from MFS):
* June 2010 (Evgeniy Ivanov)
*/
#include "fs.h"
#include <string.h>
#include <stdlib.h>
#include <minix/com.h>
#include <minix/u64.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include "const.h"
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static bit_t alloc_inode_bit(struct super_block *sp, struct inode
*parent, int is_dir);
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static void free_inode_bit(struct super_block *sp, bit_t bit_returned,
int is_dir);
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static void wipe_inode(struct inode *rip);
/*===========================================================================*
* alloc_inode *
*===========================================================================*/
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struct inode *alloc_inode(struct inode *parent, mode_t bits)
{
/* Allocate a free inode on parent's dev, and return a pointer to it. */
register struct inode *rip;
register struct super_block *sp;
int inumb;
bit_t b;
static int print_oos_msg = 1;
sp = get_super(parent->i_dev); /* get pointer to super_block */
if (sp->s_rd_only) { /* can't allocate an inode on a read only device. */
err_code = EROFS;
return(NULL);
}
/* Acquire an inode from the bit map. */
b = alloc_inode_bit(sp, parent, (bits & I_TYPE) == I_DIRECTORY);
if (b == NO_BIT) {
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err_code = ENOSPC;
if (print_oos_msg)
ext2_debug("Out of i-nodes on device %d/%d\n",
major(sp->s_dev), minor(sp->s_dev));
print_oos_msg = 0; /* Don't repeat message */
return(NULL);
}
print_oos_msg = 1;
inumb = (int) b; /* be careful not to pass unshort as param */
/* Try to acquire a slot in the inode table. */
if ((rip = get_inode(NO_DEV, inumb)) == NULL) {
/* No inode table slots available. Free the inode just allocated. */
free_inode_bit(sp, b, (bits & I_TYPE) == I_DIRECTORY);
} else {
/* An inode slot is available. Put the inode just allocated into it. */
rip->i_mode = bits; /* set up RWX bits */
rip->i_links_count = NO_LINK; /* initial no links */
rip->i_uid = caller_uid; /* file's uid is owner's */
rip->i_gid = caller_gid; /* ditto group id */
rip->i_dev = parent->i_dev; /* mark which device it is on */
rip->i_sp = sp; /* pointer to super block */
/* Fields not cleared already are cleared in wipe_inode(). They have
* been put there because truncate() needs to clear the same fields if
* the file happens to be open while being truncated. It saves space
* not to repeat the code twice.
*/
wipe_inode(rip);
}
return(rip);
}
/*===========================================================================*
* free_inode *
*===========================================================================*/
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void free_inode(
register struct inode *rip /* inode to free */
)
{
/* Return an inode to the pool of unallocated inodes. */
register struct super_block *sp;
dev_t dev = rip->i_dev;
bit_t b = rip->i_num;
u16_t mode = rip->i_mode;
/* Locate the appropriate super_block. */
sp = get_super(dev);
if (b <= NO_ENTRY || b > sp->s_inodes_count)
return;
free_inode_bit(sp, b, (mode & I_TYPE) == I_DIRECTORY);
rip->i_mode = I_NOT_ALLOC; /* clear I_TYPE field */
}
static int find_group_dir(struct super_block *sp);
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static int find_group_hashalloc(struct super_block *sp, struct inode
*parent);
static int find_group_any(struct super_block *sp);
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static int find_group_orlov(struct super_block *sp, struct inode
*parent);
/*===========================================================================*
* alloc_inode_bit *
*===========================================================================*/
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static bit_t alloc_inode_bit(sp, parent, is_dir)
struct super_block *sp; /* the filesystem to allocate from */
struct inode *parent; /* parent of newly allocated inode */
int is_dir; /* inode will be a directory if it is TRUE */
{
int group;
ino_t inumber = NO_BIT;
bit_t bit;
struct buf *bp;
struct group_desc *gd;
if (sp->s_rd_only)
panic("can't alloc inode on read-only filesys.");
if (opt.mfsalloc) {
group = find_group_any(sp);
} else {
if (is_dir) {
if (opt.use_orlov) {
group = find_group_orlov(sp, parent);
} else {
group = find_group_dir(sp);
}
} else {
group = find_group_hashalloc(sp, parent);
}
}
/* Check if we have a group where to allocate an inode */
if (group == -1)
return(NO_BIT); /* no bit could be allocated */
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc block");
/* find_group_* should always return either a group with
* a free inode slot or -1, which we checked earlier.
*/
ASSERT(gd->free_inodes_count);
bp = get_block(sp->s_dev, gd->inode_bitmap, NORMAL);
bit = setbit(bp->b_bitmap, sp->s_inodes_per_group, 0);
ASSERT(bit != -1); /* group definitly contains free inode */
inumber = group * sp->s_inodes_per_group + bit + 1;
/* Extra checks before real allocation.
* Only major bug can cause problems. Since setbit changed
* bp->b_bitmap there is no way to recover from this bug.
* Should never happen.
*/
if (inumber > sp->s_inodes_count) {
panic("ext2: allocator returned inum greater, than\
total number of inodes.\n");
}
if (inumber < EXT2_FIRST_INO(sp)) {
panic("ext2: allocator tryed to use reserved inode.\n");
}
bp->b_dirt = DIRTY;
put_block(bp, MAP_BLOCK);
gd->free_inodes_count--;
sp->s_free_inodes_count--;
if (is_dir) {
gd->used_dirs_count++;
sp->s_dirs_counter++;
}
group_descriptors_dirty = DIRTY;
/* Almost the same as previous 'group' ASSERT */
ASSERT(inumber != NO_BIT);
return inumber;
}
/*===========================================================================*
* free_inode_bit *
*===========================================================================*/
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static void free_inode_bit(struct super_block *sp, bit_t bit_returned,
int is_dir)
{
/* Return an inode by turning off its bitmap bit. */
int group; /* group number of bit_returned */
int bit; /* bit_returned number within its group */
struct buf *bp;
struct group_desc *gd;
if (sp->s_rd_only)
panic("can't free bit on read-only filesys.");
/* At first search group, to which bit_returned belongs to
* and figure out in what word bit is stored.
*/
if (bit_returned > sp->s_inodes_count ||
bit_returned < EXT2_FIRST_INO(sp))
panic("trying to free inode %d beyond inodes scope.", bit_returned);
group = (bit_returned - 1) / sp->s_inodes_per_group;
bit = (bit_returned - 1) % sp->s_inodes_per_group; /* index in bitmap */
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc block");
bp = get_block(sp->s_dev, gd->inode_bitmap, NORMAL);
if (unsetbit(bp->b_bitmap, bit))
panic("Tried to free unused inode", bit_returned);
bp->b_dirt = DIRTY;
put_block(bp, MAP_BLOCK);
gd->free_inodes_count++;
sp->s_free_inodes_count++;
if (is_dir) {
gd->used_dirs_count--;
sp->s_dirs_counter--;
}
group_descriptors_dirty = DIRTY;
if (group < sp->s_igsearch)
sp->s_igsearch = group;
}
/* it's implemented very close to the linux' find_group_dir() */
static int find_group_dir(struct super_block *sp)
{
int avefreei = sp->s_free_inodes_count / sp->s_groups_count;
struct group_desc *gd, *best_gd = NULL;
int group, best_group = -1;
for (group = 0; group < sp->s_groups_count; ++group) {
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count == 0)
continue;
if (gd->free_inodes_count < avefreei)
continue;
if (!best_gd ||
gd->free_blocks_count > best_gd->free_blocks_count) {
best_gd = gd;
best_group = group;
}
}
return best_group; /* group or -1 */
}
/* Analog of ffs_hashalloc() from *BSD.
* 1) Check parent's for free inodes and blocks.
* 2) Quadradically rehash on the group number.
* 3) Make a linear search for free inode.
*/
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static int find_group_hashalloc(struct super_block *sp, struct inode *parent)
{
int ngroups = sp->s_groups_count;
struct group_desc *gd;
int group, i;
int parent_group = (parent->i_num - 1) / sp->s_inodes_per_group;
/* Try to place new inode in its parent group */
gd = get_group_desc(parent_group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count && gd->free_blocks_count)
return parent_group;
/* We can't allocate inode in the parent's group.
* Now we will try to place it in another blockgroup.
* The main idea is still to keep files from the same
* directory together and use different blockgroups for
* files from another directory, which lives in the same
* blockgroup as our parent.
* Thus we will spread things on the disk.
*/
group = (parent_group + parent->i_num) % ngroups;
/* Make quadratic probing to find a group with free inodes and blocks. */
for (i = 1; i < ngroups; i <<= 1) {
group += i;
if (group >= ngroups)
group -= ngroups;
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count && gd->free_blocks_count)
return group;
}
/* Still no group for new inode, try linear search.
* Also check parent again (but for free inodes only).
*/
group = parent_group;
for (i = 0; i < ngroups; i++, group++) {
if (group >= ngroups)
group = 0;
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count)
return group;
}
return -1;
}
/* Find first group which has free inode slot.
* This is similar to what MFS does.
*/
static int find_group_any(struct super_block *sp)
{
int ngroups = sp->s_groups_count;
struct group_desc *gd;
int group = sp->s_igsearch;
for (; group < ngroups; group++) {
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count) {
sp->s_igsearch = group;
return group;
}
}
return -1;
}
/* We try to spread first-level directories (i.e. directories in the root
* or in the directory marked as TOPDIR).
* If there are blockgroups with counts for blocks and inodes less than average
* we return a group with lowest directory count. Otherwise we either
* return a group with good free inodes and blocks counts or just a group
* with free inode.
*
* For other directories we try to find a 'good' group, we consider a group as
* a 'good' if it has enough blocks and inodes (greater than min_blocks and
* min_inodes).
*
*/
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static int find_group_orlov(struct super_block *sp, struct inode *parent)
{
int avefreei = sp->s_free_inodes_count / sp->s_groups_count;
int avefreeb = sp->s_free_blocks_count / sp->s_groups_count;
int group = -1;
int fallback_group = -1; /* Group with at least 1 free inode */
struct group_desc *gd;
int i;
if (parent->i_num == ROOT_INODE ||
parent->i_flags & EXT2_TOPDIR_FL) {
int best_group = -1;
int best_avefree_group = -1; /* Best value of avefreei/avefreeb */
int best_ndir = sp->s_inodes_per_group;
group = (unsigned int)random();
for (i = 0; i < sp->s_groups_count; i++, group++) {
if (group >= sp->s_groups_count)
group = 0;
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count == 0)
continue;
fallback_group = group;
if (gd->free_inodes_count < avefreei ||
gd->free_blocks_count < avefreeb)
continue;
best_avefree_group = group;
if (gd->used_dirs_count >= best_ndir)
continue;
best_ndir = gd->used_dirs_count;
best_group = group;
}
if (best_group >= 0)
return best_group;
if (best_avefree_group >= 0)
return best_avefree_group;
return fallback_group;
} else {
int parent_group = (parent->i_num - 1) / sp->s_inodes_per_group;
/* 2 is kind of random thing for now,
* but performance results are still good.
*/
int min_blocks = avefreeb / 2;
int min_inodes = avefreei / 2;
group = parent_group;
for (i = 0; i < sp->s_groups_count; i++, group++) {
if (group >= sp->s_groups_count)
group = 0;
gd = get_group_desc(group);
if (gd == NULL)
panic("can't get group_desc to alloc inode");
if (gd->free_inodes_count == 0)
continue;
fallback_group = group;
if (gd->free_inodes_count >= min_inodes &&
gd->free_blocks_count >= min_blocks)
return group;
}
return fallback_group;
}
return -1;
}
/*===========================================================================*
* wipe_inode *
*===========================================================================*/
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static void wipe_inode(
register struct inode *rip /* the inode to be erased */
)
{
/* Erase some fields in the inode. This function is called from alloc_inode()
* when a new inode is to be allocated, and from truncate(), when an existing
* inode is to be truncated.
*/
register int i;
rip->i_size = 0;
rip->i_update = ATIME | CTIME | MTIME; /* update all times later */
rip->i_blocks = 0;
rip->i_flags = 0;
rip->i_generation = 0;
rip->i_file_acl = 0;
rip->i_dir_acl = 0;
rip->i_faddr = 0;
for (i = 0; i < EXT2_N_BLOCKS; i++)
rip->i_block[i] = NO_BLOCK;
rip->i_block[0] = NO_BLOCK;
rip->i_dirt = DIRTY;
}