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Concurrent Multi-File Data Streams

In media spaces, video is often stored in a frame-per-file format.
When dealing with uncompressed realtime HD video streams in this format,
it is crucial that files do not get fragmented and that multiple files
a placed contiguously on disk.

When multiple streams are being ingested and played out at the same
time, it is critical that the filesystem does not cross the streams
and interleave them together as this creates seek and readahead
cache miss latency and prevents both ingest and playout from meeting
frame rate targets.

This patch set creates a "stream of files" concept into the allocator
to place all the data from a single stream contiguously on disk so
that RAID array readahead can be used effectively. Each additional
stream gets placed in different allocation groups within the
filesystem, thereby ensuring that we don't cross any streams. When
an AG fills up, we select a new AG for the stream that is not in
use.

The core of the functionality is the stream tracking - each inode
that we create in a directory needs to be associated with the
directories' stream. Hence every time we create a file, we look up
the directories' stream object and associate the new file with that
object.

Once we have a stream object for a file, we use the AG that the
stream object point to for allocations. If we can't allocate in that
AG (e.g. it is full) we move the entire stream to another AG. Other
inodes in the same stream are moved to the new AG on their next
allocation (i.e. lazy update).

Stream objects are kept in a cache and hold a reference on the
inode. Hence the inode cannot be reclaimed while there is an
outstanding stream reference. This means that on unlink we need to
remove the stream association and we also need to flush all the
associations on certain events that want to reclaim all unreferenced
inodes (e.g.  filesystem freeze).
Merge of xfs-linux-melb:xfs-kern:29096a by kenmcd.

  Concurrent Multi-File Data Streams feature check in.

/*
 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it would 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 the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_AG_H__
#define	__XFS_AG_H__

/*
 * Allocation group header
 * This is divided into three structures, placed in sequential 512-byte
 * buffers after a copy of the superblock (also in a 512-byte buffer).
 */

struct xfs_buf;
struct xfs_mount;
struct xfs_trans;

#define	XFS_AGF_MAGIC	0x58414746	/* 'XAGF' */
#define	XFS_AGI_MAGIC	0x58414749	/* 'XAGI' */
#define	XFS_AGF_VERSION	1
#define	XFS_AGI_VERSION	1

#define	XFS_AGF_GOOD_VERSION(v)	((v) == XFS_AGF_VERSION)
#define	XFS_AGI_GOOD_VERSION(v)	((v) == XFS_AGI_VERSION)

/*
 * Btree number 0 is bno, 1 is cnt.  This value gives the size of the
 * arrays below.
 */
#define	XFS_BTNUM_AGF	((int)XFS_BTNUM_CNTi + 1)

/*
 * The second word of agf_levels in the first a.g. overlaps the EFS
 * superblock's magic number.  Since the magic numbers valid for EFS
 * are > 64k, our value cannot be confused for an EFS superblock's.
 */

typedef struct xfs_agf {
	/*
	 * Common allocation group header information
	 */
	__be32		agf_magicnum;	/* magic number == XFS_AGF_MAGIC */
	__be32		agf_versionnum;	/* header version == XFS_AGF_VERSION */
	__be32		agf_seqno;	/* sequence # starting from 0 */
	__be32		agf_length;	/* size in blocks of a.g. */
	/*
	 * Freespace information
	 */
	__be32		agf_roots[XFS_BTNUM_AGF];	/* root blocks */
	__be32		agf_spare0;	/* spare field */
	__be32		agf_levels[XFS_BTNUM_AGF];	/* btree levels */
	__be32		agf_spare1;	/* spare field */
	__be32		agf_flfirst;	/* first freelist block's index */
	__be32		agf_fllast;	/* last freelist block's index */
	__be32		agf_flcount;	/* count of blocks in freelist */
	__be32		agf_freeblks;	/* total free blocks */
	__be32		agf_longest;	/* longest free space */
	__be32		agf_btreeblks;	/* # of blocks held in AGF btrees */
} xfs_agf_t;

#define	XFS_AGF_MAGICNUM	0x00000001
#define	XFS_AGF_VERSIONNUM	0x00000002
#define	XFS_AGF_SEQNO		0x00000004
#define	XFS_AGF_LENGTH		0x00000008
#define	XFS_AGF_ROOTS		0x00000010
#define	XFS_AGF_LEVELS		0x00000020
#define	XFS_AGF_FLFIRST		0x00000040
#define	XFS_AGF_FLLAST		0x00000080
#define	XFS_AGF_FLCOUNT		0x00000100
#define	XFS_AGF_FREEBLKS	0x00000200
#define	XFS_AGF_LONGEST		0x00000400
#define	XFS_AGF_BTREEBLKS	0x00000800
#define	XFS_AGF_NUM_BITS	12
#define	XFS_AGF_ALL_BITS	((1 << XFS_AGF_NUM_BITS) - 1)

/* disk block (xfs_daddr_t) in the AG */
#define XFS_AGF_DADDR(mp)	((xfs_daddr_t)(1 << (mp)->m_sectbb_log))
#define	XFS_AGF_BLOCK(mp)	XFS_HDR_BLOCK(mp, XFS_AGF_DADDR(mp))
#define	XFS_BUF_TO_AGF(bp)	((xfs_agf_t *)XFS_BUF_PTR(bp))


/*
 * Size of the unlinked inode hash table in the agi.
 */
#define	XFS_AGI_UNLINKED_BUCKETS	64

typedef struct xfs_agi {
	/*
	 * Common allocation group header information
	 */
	__be32		agi_magicnum;	/* magic number == XFS_AGI_MAGIC */
	__be32		agi_versionnum;	/* header version == XFS_AGI_VERSION */
	__be32		agi_seqno;	/* sequence # starting from 0 */
	__be32		agi_length;	/* size in blocks of a.g. */
	/*
	 * Inode information
	 * Inodes are mapped by interpreting the inode number, so no
	 * mapping data is needed here.
	 */
	__be32		agi_count;	/* count of allocated inodes */
	__be32		agi_root;	/* root of inode btree */
	__be32		agi_level;	/* levels in inode btree */
	__be32		agi_freecount;	/* number of free inodes */
	__be32		agi_newino;	/* new inode just allocated */
	__be32		agi_dirino;	/* last directory inode chunk */
	/*
	 * Hash table of inodes which have been unlinked but are
	 * still being referenced.
	 */
	__be32		agi_unlinked[XFS_AGI_UNLINKED_BUCKETS];
} xfs_agi_t;

#define	XFS_AGI_MAGICNUM	0x00000001
#define	XFS_AGI_VERSIONNUM	0x00000002
#define	XFS_AGI_SEQNO		0x00000004
#define	XFS_AGI_LENGTH		0x00000008
#define	XFS_AGI_COUNT		0x00000010
#define	XFS_AGI_ROOT		0x00000020
#define	XFS_AGI_LEVEL		0x00000040
#define	XFS_AGI_FREECOUNT	0x00000080
#define	XFS_AGI_NEWINO		0x00000100
#define	XFS_AGI_DIRINO		0x00000200
#define	XFS_AGI_UNLINKED	0x00000400
#define	XFS_AGI_NUM_BITS	11
#define	XFS_AGI_ALL_BITS	((1 << XFS_AGI_NUM_BITS) - 1)

/* disk block (xfs_daddr_t) in the AG */
#define XFS_AGI_DADDR(mp)	((xfs_daddr_t)(2 << (mp)->m_sectbb_log))
#define	XFS_AGI_BLOCK(mp)	XFS_HDR_BLOCK(mp, XFS_AGI_DADDR(mp))
#define	XFS_BUF_TO_AGI(bp)	((xfs_agi_t *)XFS_BUF_PTR(bp))

/*
 * The third a.g. block contains the a.g. freelist, an array
 * of block pointers to blocks owned by the allocation btree code.
 */
#define XFS_AGFL_DADDR(mp)	((xfs_daddr_t)(3 << (mp)->m_sectbb_log))
#define	XFS_AGFL_BLOCK(mp)	XFS_HDR_BLOCK(mp, XFS_AGFL_DADDR(mp))
#define XFS_AGFL_SIZE(mp)	((mp)->m_sb.sb_sectsize / sizeof(xfs_agblock_t))
#define	XFS_BUF_TO_AGFL(bp)	((xfs_agfl_t *)XFS_BUF_PTR(bp))

typedef struct xfs_agfl {
	__be32		agfl_bno[1];	/* actually XFS_AGFL_SIZE(mp) */
} xfs_agfl_t;

/*
 * Busy block/extent entry.  Used in perag to mark blocks that have been freed
 * but whose transactions aren't committed to disk yet.
 */
typedef struct xfs_perag_busy {
	xfs_agblock_t	busy_start;
	xfs_extlen_t	busy_length;
	struct xfs_trans *busy_tp;	/* transaction that did the free */
} xfs_perag_busy_t;

/*
 * Per-ag incore structure, copies of information in agf and agi,
 * to improve the performance of allocation group selection.
 *
 * pick sizes which fit in allocation buckets well
 */
#if (BITS_PER_LONG == 32)
#define XFS_PAGB_NUM_SLOTS	84
#elif (BITS_PER_LONG == 64)
#define XFS_PAGB_NUM_SLOTS	128
#endif

typedef struct xfs_perag
{
	char		pagf_init;	/* this agf's entry is initialized */
	char		pagi_init;	/* this agi's entry is initialized */
	char		pagf_metadata;	/* the agf is preferred to be metadata */
	char		pagi_inodeok;	/* The agi is ok for inodes */
	__uint8_t	pagf_levels[XFS_BTNUM_AGF];
					/* # of levels in bno & cnt btree */
	__uint32_t	pagf_flcount;	/* count of blocks in freelist */
	xfs_extlen_t	pagf_freeblks;	/* total free blocks */
	xfs_extlen_t	pagf_longest;	/* longest free space */
	__uint32_t	pagf_btreeblks;	/* # of blocks held in AGF btrees */
	xfs_agino_t	pagi_freecount;	/* number of free inodes */
	xfs_agino_t	pagi_count;	/* number of allocated inodes */
	int		pagb_count;	/* pagb slots in use */
#ifdef __KERNEL__
	lock_t		pagb_lock;	/* lock for pagb_list */
#endif
	xfs_perag_busy_t *pagb_list;	/* unstable blocks */
	atomic_t        pagf_fstrms;    /* # of filestreams active in this AG */
} xfs_perag_t;

#define	XFS_AG_MAXLEVELS(mp)		((mp)->m_ag_maxlevels)
#define	XFS_MIN_FREELIST_RAW(bl,cl,mp)	\
	(MIN(bl + 1, XFS_AG_MAXLEVELS(mp)) + MIN(cl + 1, XFS_AG_MAXLEVELS(mp)))
#define	XFS_MIN_FREELIST(a,mp)		\
	(XFS_MIN_FREELIST_RAW(		\
		be32_to_cpu((a)->agf_levels[XFS_BTNUM_BNOi]), \
		be32_to_cpu((a)->agf_levels[XFS_BTNUM_CNTi]), mp))
#define	XFS_MIN_FREELIST_PAG(pag,mp)	\
	(XFS_MIN_FREELIST_RAW(		\
		(uint_t)(pag)->pagf_levels[XFS_BTNUM_BNOi], \
		(uint_t)(pag)->pagf_levels[XFS_BTNUM_CNTi], mp))

#define XFS_AGB_TO_FSB(mp,agno,agbno)	\
	(((xfs_fsblock_t)(agno) << (mp)->m_sb.sb_agblklog) | (agbno))
#define	XFS_FSB_TO_AGNO(mp,fsbno)	\
	((xfs_agnumber_t)((fsbno) >> (mp)->m_sb.sb_agblklog))
#define	XFS_FSB_TO_AGBNO(mp,fsbno)	\
	((xfs_agblock_t)((fsbno) & XFS_MASK32LO((mp)->m_sb.sb_agblklog)))
#define	XFS_AGB_TO_DADDR(mp,agno,agbno)	\
	((xfs_daddr_t)XFS_FSB_TO_BB(mp, \
		(xfs_fsblock_t)(agno) * (mp)->m_sb.sb_agblocks + (agbno)))
#define	XFS_AG_DADDR(mp,agno,d)		(XFS_AGB_TO_DADDR(mp, agno, 0) + (d))

/*
 * For checking for bad ranges of xfs_daddr_t's, covering multiple
 * allocation groups or a single xfs_daddr_t that's a superblock copy.
 */
#define	XFS_AG_CHECK_DADDR(mp,d,len)	\
	((len) == 1 ? \
	    ASSERT((d) == XFS_SB_DADDR || \
		   XFS_DADDR_TO_AGBNO(mp, d) != XFS_SB_DADDR) : \
	    ASSERT(XFS_DADDR_TO_AGNO(mp, d) == \
		   XFS_DADDR_TO_AGNO(mp, (d) + (len) - 1)))

#endif	/* __XFS_AG_H__ */