nilfs2: checkpoint file (29619809) · Commits · e / devices / android_kernel_teracube_emerald

fs/nilfs2/cpfile.c

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			/*
			* cpfile.c - NILFS checkpoint file.
			*
			* Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
			*
			* This program is free software; you can redistribute it and/or modify
			* it under the terms of the GNU General Public License as published by
			* the Free Software Foundation; either version 2 of the License, or
			* (at your option) any later version.
			*
			* This program is distributed in the hope that it will be useful,
			* but WITHOUT ANY WARRANTY; without even the implied warranty of
			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
			* GNU General Public License for more details.
			*
			* You should have received a copy of the GNU General Public License
			* along with this program; if not, write to the Free Software
			* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
			*
			* Written by Koji Sato <koji@osrg.net>.
			*/

			#include <linux/kernel.h>
			#include <linux/fs.h>
			#include <linux/string.h>
			#include <linux/buffer_head.h>
			#include <linux/errno.h>
			#include <linux/nilfs2_fs.h>
			#include "mdt.h"
			#include "cpfile.h"


			static inline unsigned long
			nilfs_cpfile_checkpoints_per_block(const struct inode *cpfile)
			{
			return NILFS_MDT(cpfile)->mi_entries_per_block;
			}

			/* block number from the beginning of the file */
			static unsigned long
			nilfs_cpfile_get_blkoff(const struct inode *cpfile, __u64 cno)
			{
			__u64 tcno;

			BUG_ON(cno == 0); /* checkpoint number 0 is invalid */
			tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
			do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
			return (unsigned long)tcno;
			}

			/* offset in block */
			static unsigned long
			nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
			{
			__u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
			return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
			}

			static unsigned long
			nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
			__u64 curr,
			__u64 max)
			{
			return min_t(__u64,
			nilfs_cpfile_checkpoints_per_block(cpfile) -
			nilfs_cpfile_get_offset(cpfile, curr),
			max - curr);
			}

			static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
			__u64 cno)
			{
			return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
			}

			static unsigned int
			nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
			struct buffer_head *bh,
			void *kaddr,
			unsigned int n)
			{
			struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
			unsigned int count;

			count = le32_to_cpu(cp->cp_checkpoints_count) + n;
			cp->cp_checkpoints_count = cpu_to_le32(count);
			return count;
			}

			static unsigned int
			nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
			struct buffer_head *bh,
			void *kaddr,
			unsigned int n)
			{
			struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
			unsigned int count;

			BUG_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
			count = le32_to_cpu(cp->cp_checkpoints_count) - n;
			cp->cp_checkpoints_count = cpu_to_le32(count);
			return count;
			}

			static inline struct nilfs_cpfile_header *
			nilfs_cpfile_block_get_header(const struct inode *cpfile,
			struct buffer_head *bh,
			void *kaddr)
			{
			return kaddr + bh_offset(bh);
			}

			static struct nilfs_checkpoint *
			nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
			struct buffer_head *bh,
			void *kaddr)
			{
			return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
			NILFS_MDT(cpfile)->mi_entry_size;
			}

			static void nilfs_cpfile_block_init(struct inode *cpfile,
			struct buffer_head *bh,
			void *kaddr)
			{
			struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
			size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
			int n = nilfs_cpfile_checkpoints_per_block(cpfile);

			while (n-- > 0) {
			nilfs_checkpoint_set_invalid(cp);
			cp = (void *)cp + cpsz;
			}
			}

			static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
			struct buffer_head **bhp)
			{
			return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
			}

			static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
			__u64 cno,
			int create,
			struct buffer_head **bhp)
			{
			return nilfs_mdt_get_block(cpfile,
			nilfs_cpfile_get_blkoff(cpfile, cno),
			create, nilfs_cpfile_block_init, bhp);
			}

			static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
			__u64 cno)
			{
			return nilfs_mdt_delete_block(cpfile,
			nilfs_cpfile_get_blkoff(cpfile, cno));
			}

			/**
			* nilfs_cpfile_get_checkpoint - get a checkpoint
			* @cpfile: inode of checkpoint file
			* @cno: checkpoint number
			* @create: create flag
			* @cpp: pointer to a checkpoint
			* @bhp: pointer to a buffer head
			*
			* Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
			* specified by @cno. A new checkpoint will be created if @cno is the current
			* checkpoint number and @create is nonzero.
			*
			* Return Value: On success, 0 is returned, and the checkpoint and the
			* buffer head of the buffer on which the checkpoint is located are stored in
			* the place pointed by @cpp and @bhp, respectively. On error, one of the
			* following negative error codes is returned.
			*
			* %-EIO - I/O error.
			*
			* %-ENOMEM - Insufficient amount of memory available.
			*
			* %-ENOENT - No such checkpoint.
			*/
			int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
			__u64 cno,
			int create,
			struct nilfs_checkpoint **cpp,
			struct buffer_head **bhp)
			{
			struct buffer_head header_bh, cp_bh;
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			void *kaddr;
			int ret;

			BUG_ON(cno < 1 \|\| cno > nilfs_mdt_cno(cpfile) \|\|
			(cno < nilfs_mdt_cno(cpfile) && create));

			down_write(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
			if (ret < 0)
			goto out_sem;
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, create, &cp_bh);
			if (ret < 0)
			goto out_header;
			kaddr = kmap(cp_bh->b_page);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
			if (nilfs_checkpoint_invalid(cp)) {
			if (!create) {
			kunmap(cp_bh->b_page);
			brelse(cp_bh);
			ret = -ENOENT;
			goto out_header;
			}
			/* a newly-created checkpoint */
			nilfs_checkpoint_clear_invalid(cp);
			if (!nilfs_cpfile_is_in_first(cpfile, cno))
			nilfs_cpfile_block_add_valid_checkpoints(cpfile, cp_bh,
			kaddr, 1);
			nilfs_mdt_mark_buffer_dirty(cp_bh);

			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, header_bh,
			kaddr);
			le64_add_cpu(&header->ch_ncheckpoints, 1);
			kunmap_atomic(kaddr, KM_USER0);
			nilfs_mdt_mark_buffer_dirty(header_bh);
			nilfs_mdt_mark_dirty(cpfile);
			}

			if (cpp != NULL)
			*cpp = cp;
			*bhp = cp_bh;

			out_header:
			brelse(header_bh);

			out_sem:
			up_write(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			/**
			* nilfs_cpfile_put_checkpoint - put a checkpoint
			* @cpfile: inode of checkpoint file
			* @cno: checkpoint number
			* @bh: buffer head
			*
			* Description: nilfs_cpfile_put_checkpoint() releases the checkpoint
			* specified by @cno. @bh must be the buffer head which has been returned by
			* a previous call to nilfs_cpfile_get_checkpoint() with @cno.
			*/
			void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
			struct buffer_head *bh)
			{
			kunmap(bh->b_page);
			brelse(bh);
			}

			/**
			* nilfs_cpfile_delete_checkpoints - delete checkpoints
			* @cpfile: inode of checkpoint file
			* @start: start checkpoint number
			* @end: end checkpoint numer
			*
			* Description: nilfs_cpfile_delete_checkpoints() deletes the checkpoints in
			* the period from @start to @end, excluding @end itself. The checkpoints
			* which have been already deleted are ignored.
			*
			* Return Value: On success, 0 is returned. On error, one of the following
			* negative error codes is returned.
			*
			* %-EIO - I/O error.
			*
			* %-ENOMEM - Insufficient amount of memory available.
			*
			* %-EINVAL - invalid checkpoints.
			*/
			int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
			__u64 start,
			__u64 end)
			{
			struct buffer_head header_bh, cp_bh;
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
			__u64 cno;
			void *kaddr;
			unsigned long tnicps;
			int ret, ncps, nicps, count, i;

			if ((start == 0) \|\| (start > end)) {
			printk(KERN_CRIT "%s: start = %llu, end = %llu\n",
			__func__,
			(unsigned long long)start,
			(unsigned long long)end);
			BUG();
			}

			/* cannot delete the latest checkpoint */
			if (start == nilfs_mdt_cno(cpfile) - 1)
			return -EPERM;

			down_write(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
			if (ret < 0)
			goto out_sem;
			tnicps = 0;

			for (cno = start; cno < end; cno += ncps) {
			ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
			if (ret < 0) {
			if (ret != -ENOENT)
			goto out_sem;
			/* skip hole */
			ret = 0;
			continue;
			}

			kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(
			cpfile, cno, cp_bh, kaddr);
			nicps = 0;
			for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
			BUG_ON(nilfs_checkpoint_snapshot(cp));
			if (!nilfs_checkpoint_invalid(cp)) {
			nilfs_checkpoint_set_invalid(cp);
			nicps++;
			}
			}
			if (nicps > 0) {
			tnicps += nicps;
			nilfs_mdt_mark_buffer_dirty(cp_bh);
			nilfs_mdt_mark_dirty(cpfile);
			if (!nilfs_cpfile_is_in_first(cpfile, cno) &&
			(count = nilfs_cpfile_block_sub_valid_checkpoints(
			cpfile, cp_bh, kaddr, nicps)) == 0) {
			/* make hole */
			kunmap_atomic(kaddr, KM_USER0);
			brelse(cp_bh);
			ret = nilfs_cpfile_delete_checkpoint_block(
			cpfile, cno);
			if (ret == 0)
			continue;
			printk(KERN_ERR "%s: cannot delete block\n",
			__func__);
			goto out_sem;
			}
			}

			kunmap_atomic(kaddr, KM_USER0);
			brelse(cp_bh);
			}

			if (tnicps > 0) {
			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, header_bh,
			kaddr);
			le64_add_cpu(&header->ch_ncheckpoints, -tnicps);
			nilfs_mdt_mark_buffer_dirty(header_bh);
			nilfs_mdt_mark_dirty(cpfile);
			kunmap_atomic(kaddr, KM_USER0);
			}
			brelse(header_bh);

			out_sem:
			up_write(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
			struct nilfs_checkpoint *cp,
			struct nilfs_cpinfo *ci)
			{
			ci->ci_flags = le32_to_cpu(cp->cp_flags);
			ci->ci_cno = le64_to_cpu(cp->cp_cno);
			ci->ci_create = le64_to_cpu(cp->cp_create);
			ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
			ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
			ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
			ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
			}

			static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 cno,
			struct nilfs_cpinfo *ci, size_t nci)
			{
			struct nilfs_checkpoint *cp;
			struct buffer_head *bh;
			size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
			__u64 cur_cno = nilfs_mdt_cno(cpfile);
			void *kaddr;
			int n, ret;
			int ncps, i;

			down_read(&NILFS_MDT(cpfile)->mi_sem);

			for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
			ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
			if (ret < 0) {
			if (ret != -ENOENT)
			goto out;
			continue; /* skip hole */
			}

			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
			for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
			if (!nilfs_checkpoint_invalid(cp))
			nilfs_cpfile_checkpoint_to_cpinfo(
			cpfile, cp, &ci[n++]);
			}
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);
			}

			ret = n;

			out:
			up_read(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 cno,
			struct nilfs_cpinfo *ci, size_t nci)
			{
			struct buffer_head *bh;
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			__u64 curr, next;
			unsigned long curr_blkoff, next_blkoff;
			void *kaddr;
			int n, ret;

			down_read(&NILFS_MDT(cpfile)->mi_sem);

			if (cno == 0) {
			ret = nilfs_cpfile_get_header_block(cpfile, &bh);
			if (ret < 0)
			goto out;
			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
			curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);
			if (curr == 0) {
			ret = 0;
			goto out;
			}
			} else
			curr = cno;
			curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
			if (ret < 0)
			goto out;
			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			for (n = 0; n < nci; n++) {
			cp = nilfs_cpfile_block_get_checkpoint(
			cpfile, curr, bh, kaddr);
			nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, &ci[n]);
			next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
			if (next == 0) {
			curr = next;
			n++;
			break;
			}
			next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
			if (curr_blkoff != next_blkoff) {
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
			0, &bh);
			if (ret < 0)
			goto out;
			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			}
			curr = next;
			curr_blkoff = next_blkoff;
			}
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);
			ret = n;

			out:
			up_read(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			/**
			* nilfs_cpfile_get_cpinfo -
			* @cpfile:
			* @cno:
			* @ci:
			* @nci:
			*/
			ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile,
			__u64 cno, int mode,
			struct nilfs_cpinfo *ci, size_t nci)
			{
			switch (mode) {
			case NILFS_CHECKPOINT:
			return nilfs_cpfile_do_get_cpinfo(cpfile, cno, ci, nci);
			case NILFS_SNAPSHOT:
			return nilfs_cpfile_do_get_ssinfo(cpfile, cno, ci, nci);
			default:
			return -EINVAL;
			}
			}

			/**
			* nilfs_cpfile_delete_checkpoint -
			* @cpfile:
			* @cno:
			*/
			int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
			{
			struct nilfs_cpinfo ci;
			ssize_t nci;
			int ret;

			/* checkpoint number 0 is invalid */
			if (cno == 0)
			return -ENOENT;
			nci = nilfs_cpfile_do_get_cpinfo(cpfile, cno, &ci, 1);
			if (nci < 0)
			return nci;
			else if (nci == 0 \|\| ci.ci_cno != cno)
			return -ENOENT;

			/* cannot delete the latest checkpoint nor snapshots */
			ret = nilfs_cpinfo_snapshot(&ci);
			if (ret < 0)
			return ret;
			else if (ret > 0 \|\| cno == nilfs_mdt_cno(cpfile) - 1)
			return -EPERM;

			return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
			}

			static struct nilfs_snapshot_list *
			nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
			__u64 cno,
			struct buffer_head *bh,
			void *kaddr)
			{
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			struct nilfs_snapshot_list *list;

			if (cno != 0) {
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
			list = &cp->cp_snapshot_list;
			} else {
			header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
			list = &header->ch_snapshot_list;
			}
			return list;
			}

			static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
			{
			struct buffer_head header_bh, curr_bh, prev_bh, cp_bh;
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			struct nilfs_snapshot_list *list;
			__u64 curr, prev;
			unsigned long curr_blkoff, prev_blkoff;
			void *kaddr;
			int ret;

			down_write(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
			if (ret < 0)
			goto out_sem;
			kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
			if (nilfs_checkpoint_invalid(cp)) {
			ret = -ENOENT;
			kunmap_atomic(kaddr, KM_USER0);
			goto out_cp;
			}
			if (nilfs_checkpoint_snapshot(cp)) {
			ret = 0;
			kunmap_atomic(kaddr, KM_USER0);
			goto out_cp;
			}
			kunmap_atomic(kaddr, KM_USER0);

			ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
			if (ret < 0)
			goto out_cp;
			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
			list = &header->ch_snapshot_list;
			curr_bh = header_bh;
			get_bh(curr_bh);
			curr = 0;
			curr_blkoff = 0;
			prev = le64_to_cpu(list->ssl_prev);
			while (prev > cno) {
			prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
			curr = prev;
			if (curr_blkoff != prev_blkoff) {
			kunmap_atomic(kaddr, KM_USER0);
			brelse(curr_bh);
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
			0, &curr_bh);
			if (ret < 0)
			goto out_header;
			kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
			}
			curr_blkoff = prev_blkoff;
			cp = nilfs_cpfile_block_get_checkpoint(
			cpfile, curr, curr_bh, kaddr);
			list = &cp->cp_snapshot_list;
			prev = le64_to_cpu(list->ssl_prev);
			}
			kunmap_atomic(kaddr, KM_USER0);

			if (prev != 0) {
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
			&prev_bh);
			if (ret < 0)
			goto out_curr;
			} else {
			prev_bh = header_bh;
			get_bh(prev_bh);
			}

			kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
			list = nilfs_cpfile_block_get_snapshot_list(
			cpfile, curr, curr_bh, kaddr);
			list->ssl_prev = cpu_to_le64(cno);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
			cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
			cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
			nilfs_checkpoint_set_snapshot(cp);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
			list = nilfs_cpfile_block_get_snapshot_list(
			cpfile, prev, prev_bh, kaddr);
			list->ssl_next = cpu_to_le64(cno);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
			le64_add_cpu(&header->ch_nsnapshots, 1);
			kunmap_atomic(kaddr, KM_USER0);

			nilfs_mdt_mark_buffer_dirty(prev_bh);
			nilfs_mdt_mark_buffer_dirty(curr_bh);
			nilfs_mdt_mark_buffer_dirty(cp_bh);
			nilfs_mdt_mark_buffer_dirty(header_bh);
			nilfs_mdt_mark_dirty(cpfile);

			brelse(prev_bh);

			out_curr:
			brelse(curr_bh);

			out_header:
			brelse(header_bh);

			out_cp:
			brelse(cp_bh);

			out_sem:
			up_write(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
			{
			struct buffer_head header_bh, next_bh, prev_bh, cp_bh;
			struct nilfs_cpfile_header *header;
			struct nilfs_checkpoint *cp;
			struct nilfs_snapshot_list *list;
			__u64 next, prev;
			void *kaddr;
			int ret;

			down_write(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
			if (ret < 0)
			goto out_sem;
			kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
			if (nilfs_checkpoint_invalid(cp)) {
			ret = -ENOENT;
			kunmap_atomic(kaddr, KM_USER0);
			goto out_cp;
			}
			if (!nilfs_checkpoint_snapshot(cp)) {
			ret = 0;
			kunmap_atomic(kaddr, KM_USER0);
			goto out_cp;
			}

			list = &cp->cp_snapshot_list;
			next = le64_to_cpu(list->ssl_next);
			prev = le64_to_cpu(list->ssl_prev);
			kunmap_atomic(kaddr, KM_USER0);

			ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
			if (ret < 0)
			goto out_cp;
			if (next != 0) {
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
			&next_bh);
			if (ret < 0)
			goto out_header;
			} else {
			next_bh = header_bh;
			get_bh(next_bh);
			}
			if (prev != 0) {
			ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
			&prev_bh);
			if (ret < 0)
			goto out_next;
			} else {
			prev_bh = header_bh;
			get_bh(prev_bh);
			}

			kaddr = kmap_atomic(next_bh->b_page, KM_USER0);
			list = nilfs_cpfile_block_get_snapshot_list(
			cpfile, next, next_bh, kaddr);
			list->ssl_prev = cpu_to_le64(prev);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
			list = nilfs_cpfile_block_get_snapshot_list(
			cpfile, prev, prev_bh, kaddr);
			list->ssl_next = cpu_to_le64(next);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
			cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
			cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
			nilfs_checkpoint_clear_snapshot(cp);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
			le64_add_cpu(&header->ch_nsnapshots, -1);
			kunmap_atomic(kaddr, KM_USER0);

			nilfs_mdt_mark_buffer_dirty(next_bh);
			nilfs_mdt_mark_buffer_dirty(prev_bh);
			nilfs_mdt_mark_buffer_dirty(cp_bh);
			nilfs_mdt_mark_buffer_dirty(header_bh);
			nilfs_mdt_mark_dirty(cpfile);

			brelse(prev_bh);

			out_next:
			brelse(next_bh);

			out_header:
			brelse(header_bh);

			out_cp:
			brelse(cp_bh);

			out_sem:
			up_write(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			/**
			* nilfs_cpfile_is_snapshot -
			* @cpfile: inode of checkpoint file
			* @cno: checkpoint number
			*
			* Description:
			*
			* Return Value: On success, 1 is returned if the checkpoint specified by
			* @cno is a snapshot, or 0 if not. On error, one of the following negative
			* error codes is returned.
			*
			* %-EIO - I/O error.
			*
			* %-ENOMEM - Insufficient amount of memory available.
			*
			* %-ENOENT - No such checkpoint.
			*/
			int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
			{
			struct buffer_head *bh;
			struct nilfs_checkpoint *cp;
			void *kaddr;
			int ret;

			down_read(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
			if (ret < 0)
			goto out;
			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
			ret = nilfs_checkpoint_snapshot(cp);
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);

			out:
			up_read(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

			/**
			* nilfs_cpfile_change_cpmode - change checkpoint mode
			* @cpfile: inode of checkpoint file
			* @cno: checkpoint number
			* @status: mode of checkpoint
			*
			* Description: nilfs_change_cpmode() changes the mode of the checkpoint
			* specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
			*
			* Return Value: On success, 0 is returned. On error, one of the following
			* negative error codes is returned.
			*
			* %-EIO - I/O error.
			*
			* %-ENOMEM - Insufficient amount of memory available.
			*
			* %-ENOENT - No such checkpoint.
			*/
			int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
			{
			struct the_nilfs *nilfs;
			int ret;

			nilfs = NILFS_MDT(cpfile)->mi_nilfs;

			switch (mode) {
			case NILFS_CHECKPOINT:
			/*
			* Check for protecting existing snapshot mounts:
			* bd_mount_sem is used to make this operation atomic and
			* exclusive with a new mount job. Though it doesn't cover
			* umount, it's enough for the purpose.
			*/
			down(&nilfs->ns_bdev->bd_mount_sem);
			if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
			/* Current implementation does not have to protect
			plain read-only mounts since they are exclusive
			with a read/write mount and are protected from the
			cleaner. */
			ret = -EBUSY;
			} else
			ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
			up(&nilfs->ns_bdev->bd_mount_sem);
			return ret;
			case NILFS_SNAPSHOT:
			return nilfs_cpfile_set_snapshot(cpfile, cno);
			default:
			return -EINVAL;
			}
			}

			/**
			* nilfs_cpfile_get_stat - get checkpoint statistics
			* @cpfile: inode of checkpoint file
			* @stat: pointer to a structure of checkpoint statistics
			*
			* Description: nilfs_cpfile_get_stat() returns information about checkpoints.
			*
			* Return Value: On success, 0 is returned, and checkpoints information is
			* stored in the place pointed by @stat. On error, one of the following
			* negative error codes is returned.
			*
			* %-EIO - I/O error.
			*
			* %-ENOMEM - Insufficient amount of memory available.
			*/
			int nilfs_cpfile_get_stat(struct inode cpfile, struct nilfs_cpstat cpstat)
			{
			struct buffer_head *bh;
			struct nilfs_cpfile_header *header;
			void *kaddr;
			int ret;

			down_read(&NILFS_MDT(cpfile)->mi_sem);

			ret = nilfs_cpfile_get_header_block(cpfile, &bh);
			if (ret < 0)
			goto out_sem;
			kaddr = kmap_atomic(bh->b_page, KM_USER0);
			header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
			cpstat->cs_cno = nilfs_mdt_cno(cpfile);
			cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
			cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
			kunmap_atomic(kaddr, KM_USER0);
			brelse(bh);

			out_sem:
			up_read(&NILFS_MDT(cpfile)->mi_sem);
			return ret;
			}

fs/nilfs2/cpfile.h

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