/*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions
   * of the GNU General Public License version 2.
   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/writeback.h>
  #include <linux/swap.h>
  #include <linux/delay.h>
  #include <linux/bio.h>
  #include <linux/gfs2_ondisk.h>
  
  #include "gfs2.h"
  #include "incore.h"
  #include "glock.h"
  #include "glops.h"
  #include "inode.h"
  #include "log.h"
  #include "lops.h"
  #include "meta_io.h"
  #include "rgrp.h"
  #include "trans.h"
  #include "util.h"
  #include "trace_gfs2.h"
  
  static int gfs2_aspace_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct buffer_head *bh, *head;
  	int nr_underway = 0;
  	int write_op = REQ_META | REQ_PRIO |
  		(wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
  
  	BUG_ON(!PageLocked(page));
  	BUG_ON(!page_has_buffers(page));
  
  	head = page_buffers(page);
  	bh = head;
  
  	do {
  		if (!buffer_mapped(bh))
  			continue;
  		/*
  		 * If it's a fully non-blocking write attempt and we cannot
  		 * lock the buffer then redirty the page.  Note that this can
  		 * potentially cause a busy-wait loop from flusher thread and kswapd
  		 * activity, but those code paths have their own higher-level
  		 * throttling.
  		 */
  		if (wbc->sync_mode != WB_SYNC_NONE) {
  			lock_buffer(bh);
  		} else if (!trylock_buffer(bh)) {
  			redirty_page_for_writepage(wbc, page);
  			continue;
  		}
  		if (test_clear_buffer_dirty(bh)) {
  			mark_buffer_async_write(bh);
  		} else {
  			unlock_buffer(bh);
  		}
  	} while ((bh = bh->b_this_page) != head);
  
  	/*
  	 * The page and its buffers are protected by PageWriteback(), so we can
  	 * drop the bh refcounts early.
  	 */
  	BUG_ON(PageWriteback(page));
  	set_page_writeback(page);
  
  	do {
  		struct buffer_head *next = bh->b_this_page;
  		if (buffer_async_write(bh)) {
  			submit_bh(write_op, bh);
  			nr_underway++;
  		}
  		bh = next;
  	} while (bh != head);
  	unlock_page(page);
  
  	if (nr_underway == 0)
  		end_page_writeback(page);
  
  	return 0;
  }
  
  const struct address_space_operations gfs2_meta_aops = {
  	.writepage = gfs2_aspace_writepage,
  	.releasepage = gfs2_releasepage,
  };
  
  const struct address_space_operations gfs2_rgrp_aops = {
  	.writepage = gfs2_aspace_writepage,
  	.releasepage = gfs2_releasepage,
  };
  
  /**
   * gfs2_getbuf - Get a buffer with a given address space
   * @gl: the glock
   * @blkno: the block number (filesystem scope)
   * @create: 1 if the buffer should be created
   *
   * Returns: the buffer
   */
  
  struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno, int create)
  {
  	struct address_space *mapping = gfs2_glock2aspace(gl);
  	struct gfs2_sbd *sdp = gl->gl_sbd;
  	struct page *page;
  	struct buffer_head *bh;
  	unsigned int shift;
  	unsigned long index;
  	unsigned int bufnum;
  
  	if (mapping == NULL)
  		mapping = &sdp->sd_aspace;
  
  	shift = PAGE_CACHE_SHIFT - sdp->sd_sb.sb_bsize_shift;
  	index = blkno >> shift;             /* convert block to page */
  	bufnum = blkno - (index << shift);  /* block buf index within page */
  
  	if (create) {
  		for (;;) {
  			page = grab_cache_page(mapping, index);
  			if (page)
  				break;
  			yield();
  		}
  	} else {
  		page = find_lock_page(mapping, index);
  		if (!page)
  			return NULL;
  	}
  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, sdp->sd_sb.sb_bsize, 0);
  
  	/* Locate header for our buffer within our page */
  	for (bh = page_buffers(page); bufnum--; bh = bh->b_this_page)
  		/* Do nothing */;
  	get_bh(bh);
  
  	if (!buffer_mapped(bh))
  		map_bh(bh, sdp->sd_vfs, blkno);
  
  	unlock_page(page);
  	mark_page_accessed(page);
  	page_cache_release(page);
  
  	return bh;
  }
  
  static void meta_prep_new(struct buffer_head *bh)
  {
  	struct gfs2_meta_header *mh = (struct gfs2_meta_header *)bh->b_data;
  
  	lock_buffer(bh);
  	clear_buffer_dirty(bh);
  	set_buffer_uptodate(bh);
  	unlock_buffer(bh);
  
  	mh->mh_magic = cpu_to_be32(GFS2_MAGIC);
  }
  
  /**
   * gfs2_meta_new - Get a block
   * @gl: The glock associated with this block
   * @blkno: The block number
   *
   * Returns: The buffer
   */
  
  struct buffer_head *gfs2_meta_new(struct gfs2_glock *gl, u64 blkno)
  {
  	struct buffer_head *bh;
  	bh = gfs2_getbuf(gl, blkno, CREATE);
  	meta_prep_new(bh);
  	return bh;
  }
  
  /**
   * gfs2_meta_read - Read a block from disk
   * @gl: The glock covering the block
   * @blkno: The block number
   * @flags: flags
   * @bhp: the place where the buffer is returned (NULL on failure)
   *
   * Returns: errno
   */
  
  int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags,
  		   struct buffer_head **bhp)
  {
  	struct gfs2_sbd *sdp = gl->gl_sbd;
  	struct buffer_head *bh;
  
  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
  		*bhp = NULL;
  		return -EIO;
  	}
  
  	*bhp = bh = gfs2_getbuf(gl, blkno, CREATE);
  
  	lock_buffer(bh);
  	if (buffer_uptodate(bh)) {
  		unlock_buffer(bh);
  		return 0;
  	}
  	bh->b_end_io = end_buffer_read_sync;
  	get_bh(bh);
  	submit_bh(READ_SYNC | REQ_META | REQ_PRIO, bh);
  	if (!(flags & DIO_WAIT))
  		return 0;
  
  	wait_on_buffer(bh);
  	if (unlikely(!buffer_uptodate(bh))) {
  		struct gfs2_trans *tr = current->journal_info;
  		if (tr && tr->tr_touched)
  			gfs2_io_error_bh(sdp, bh);
  		brelse(bh);
  		*bhp = NULL;
  		return -EIO;
  	}
  
  	return 0;
  }
  
  /**
   * gfs2_meta_wait - Reread a block from disk
   * @sdp: the filesystem
   * @bh: The block to wait for
   *
   * Returns: errno
   */
  
  int gfs2_meta_wait(struct gfs2_sbd *sdp, struct buffer_head *bh)
  {
  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
  		return -EIO;
  
  	wait_on_buffer(bh);
  
  	if (!buffer_uptodate(bh)) {
  		struct gfs2_trans *tr = current->journal_info;
  		if (tr && tr->tr_touched)
  			gfs2_io_error_bh(sdp, bh);
  		return -EIO;
  	}
  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
  		return -EIO;
  
  	return 0;
  }
  
  void gfs2_remove_from_journal(struct buffer_head *bh, struct gfs2_trans *tr, int meta)
  {
  	struct address_space *mapping = bh->b_page->mapping;
  	struct gfs2_sbd *sdp = gfs2_mapping2sbd(mapping);
  	struct gfs2_bufdata *bd = bh->b_private;
  	int was_pinned = 0;
  
  	if (test_clear_buffer_pinned(bh)) {
  		trace_gfs2_pin(bd, 0);
  		atomic_dec(&sdp->sd_log_pinned);
  		list_del_init(&bd->bd_list);
  		if (meta) {
  			gfs2_assert_warn(sdp, sdp->sd_log_num_buf);
  			sdp->sd_log_num_buf--;
  			tr->tr_num_buf_rm++;
  		} else {
  			gfs2_assert_warn(sdp, sdp->sd_log_num_databuf);
  			sdp->sd_log_num_databuf--;
  			tr->tr_num_databuf_rm++;
  		}
  		tr->tr_touched = 1;
  		was_pinned = 1;
  		brelse(bh);
  	}
  	if (bd) {
  		spin_lock(&sdp->sd_ail_lock);
  		if (bd->bd_tr) {
  			gfs2_trans_add_revoke(sdp, bd);
  		} else if (was_pinned) {
  			bh->b_private = NULL;
  			kmem_cache_free(gfs2_bufdata_cachep, bd);
  		}
  		spin_unlock(&sdp->sd_ail_lock);
  	}
  	clear_buffer_dirty(bh);
  	clear_buffer_uptodate(bh);
  }
  
  /**
   * gfs2_meta_wipe - make inode's buffers so they aren't dirty/pinned anymore
   * @ip: the inode who owns the buffers
   * @bstart: the first buffer in the run
   * @blen: the number of buffers in the run
   *
   */
  
  void gfs2_meta_wipe(struct gfs2_inode *ip, u64 bstart, u32 blen)
  {
  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
  	struct buffer_head *bh;
  
  	while (blen) {
  		bh = gfs2_getbuf(ip->i_gl, bstart, NO_CREATE);
  		if (bh) {
  			lock_buffer(bh);
  			gfs2_log_lock(sdp);
  			gfs2_remove_from_journal(bh, current->journal_info, 1);
  			gfs2_log_unlock(sdp);
  			unlock_buffer(bh);
  			brelse(bh);
  		}
  
  		bstart++;
  		blen--;
  	}
  }
  
  /**
   * gfs2_meta_indirect_buffer - Get a metadata buffer
   * @ip: The GFS2 inode
   * @height: The level of this buf in the metadata (indir addr) tree (if any)
   * @num: The block number (device relative) of the buffer
   * @bhp: the buffer is returned here
   *
   * Returns: errno
   */
  
  int gfs2_meta_indirect_buffer(struct gfs2_inode *ip, int height, u64 num,
  			      struct buffer_head **bhp)
  {
  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
  	struct gfs2_glock *gl = ip->i_gl;
  	struct buffer_head *bh;
  	int ret = 0;
  	u32 mtype = height ? GFS2_METATYPE_IN : GFS2_METATYPE_DI;
  
  	ret = gfs2_meta_read(gl, num, DIO_WAIT, &bh);
  	if (ret == 0 && gfs2_metatype_check(sdp, bh, mtype)) {
  		brelse(bh);
  		ret = -EIO;
  	}
  	*bhp = bh;
  	return ret;
  }
  
  /**
   * gfs2_meta_ra - start readahead on an extent of a file
   * @gl: the glock the blocks belong to
   * @dblock: the starting disk block
   * @extlen: the number of blocks in the extent
   *
   * returns: the first buffer in the extent
   */
  
  struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen)
  {
  	struct gfs2_sbd *sdp = gl->gl_sbd;
  	struct buffer_head *first_bh, *bh;
  	u32 max_ra = gfs2_tune_get(sdp, gt_max_readahead) >>
  			  sdp->sd_sb.sb_bsize_shift;
  
  	BUG_ON(!extlen);
  
  	if (max_ra < 1)
  		max_ra = 1;
  	if (extlen > max_ra)
  		extlen = max_ra;
  
  	first_bh = gfs2_getbuf(gl, dblock, CREATE);
  
  	if (buffer_uptodate(first_bh))
  		goto out;
  	if (!buffer_locked(first_bh))
  		ll_rw_block(READ_SYNC | REQ_META, 1, &first_bh);
  
  	dblock++;
  	extlen--;
  
  	while (extlen) {
  		bh = gfs2_getbuf(gl, dblock, CREATE);
  
  		if (!buffer_uptodate(bh) && !buffer_locked(bh))
  			ll_rw_block(READA | REQ_META, 1, &bh);
  		brelse(bh);
  		dblock++;
  		extlen--;
  		if (!buffer_locked(first_bh) && buffer_uptodate(first_bh))
  			goto out;
  	}
  
  	wait_on_buffer(first_bh);
  out:
  	return first_bh;
  }