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Commit 23253068 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: improve smp scalability for inode generation 



->s_next_generation is protected by s_next_gen_lock but its usage
pattern is very primitive.  We don't actually need sequentially
increasing new generation numbers, so let's use prandom_u32() instead.

Reported-by: default avatarDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent d77147ff

fs/ext4/ext4.h

+0 −2
Original line number Original line Diff line number Diff line
@@ -1355,8 +1355,6 @@ struct ext4_sb_info { 
	int s_first_ino;

	int s_first_ino;

	unsigned int s_inode_readahead_blks;

	unsigned int s_inode_readahead_blks;

	unsigned int s_inode_goal;

	unsigned int s_inode_goal;

	spinlock_t s_next_gen_lock;

	u32 s_next_generation;

	u32 s_hash_seed[4];

	u32 s_hash_seed[4];

	int s_def_hash_version;

	int s_def_hash_version;

	int s_hash_unsigned;	/* 3 if hash should be signed, 0 if not */

	int s_hash_unsigned;	/* 3 if hash should be signed, 0 if not */

fs/ext4/ialloc.c

+1 −3
Original line number Original line Diff line number Diff line
@@ -1138,9 +1138,7 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir, 
			   inode->i_ino);

			   inode->i_ino);

		goto out;

		goto out;

	}

	}

	spin_lock(&sbi->s_next_gen_lock);

	inode->i_generation = prandom_u32();

	inode->i_generation = sbi->s_next_generation++;

	spin_unlock(&sbi->s_next_gen_lock);





	/* Precompute checksum seed for inode metadata */

	/* Precompute checksum seed for inode metadata */

	if (ext4_has_metadata_csum(sb)) {

	if (ext4_has_metadata_csum(sb)) {

fs/ext4/ioctl.c

+3 −5
Original line number Original line Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/mount.h>

#include <linux/mount.h>

#include <linux/file.h>

#include <linux/file.h>

#include <linux/quotaops.h>

#include <linux/quotaops.h>

#include <linux/random.h>

#include <linux/uuid.h>

#include <linux/uuid.h>

#include <linux/uaccess.h>

#include <linux/uaccess.h>

#include <linux/delay.h>

#include <linux/delay.h>
@@ -98,7 +99,6 @@ static long swap_inode_boot_loader(struct super_block *sb, 
	int err;

	int err;

	struct inode *inode_bl;

	struct inode *inode_bl;

	struct ext4_inode_info *ei_bl;

	struct ext4_inode_info *ei_bl;

	struct ext4_sb_info *sbi = EXT4_SB(sb);





	if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode))

	if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode))

		return -EINVAL;

		return -EINVAL;
@@ -157,10 +157,8 @@ static long swap_inode_boot_loader(struct super_block *sb, 




	inode->i_ctime = inode_bl->i_ctime = current_time(inode);

	inode->i_ctime = inode_bl->i_ctime = current_time(inode);





	spin_lock(&sbi->s_next_gen_lock);

	inode->i_generation = prandom_u32();

	inode->i_generation = sbi->s_next_generation++;

	inode_bl->i_generation = prandom_u32();

	inode_bl->i_generation = sbi->s_next_generation++;

	spin_unlock(&sbi->s_next_gen_lock);





	ext4_discard_preallocations(inode);

	ext4_discard_preallocations(inode);

fs/ext4/super.c

+0 −2
Original line number Original line Diff line number Diff line
@@ -3982,8 +3982,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 
	}

	}





	sbi->s_gdb_count = db_count;

	sbi->s_gdb_count = db_count;

	get_random_bytes(&sbi->s_next_generation, sizeof(u32));

	spin_lock_init(&sbi->s_next_gen_lock);





	timer_setup(&sbi->s_err_report, print_daily_error_info, 0);

	timer_setup(&sbi->s_err_report, print_daily_error_info, 0);