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/*
* Copyright (c) 2006-2007 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_FILESTREAM_H__
#define __XFS_FILESTREAM_H__
#ifdef __KERNEL__
struct xfs_mount;
struct xfs_inode;
struct xfs_perag;
struct xfs_bmalloca;
#ifdef XFS_FILESTREAMS_TRACE
#define XFS_FSTRM_KTRACE_INFO 1
#define XFS_FSTRM_KTRACE_AGSCAN 2
#define XFS_FSTRM_KTRACE_AGPICK1 3
#define XFS_FSTRM_KTRACE_AGPICK2 4
#define XFS_FSTRM_KTRACE_UPDATE 5
#define XFS_FSTRM_KTRACE_FREE 6
#define XFS_FSTRM_KTRACE_ITEM_LOOKUP 7
#define XFS_FSTRM_KTRACE_ASSOCIATE 8
#define XFS_FSTRM_KTRACE_MOVEAG 9
#define XFS_FSTRM_KTRACE_ORPHAN 10
#define XFS_FSTRM_KTRACE_SIZE 16384
extern ktrace_t *xfs_filestreams_trace_buf;
#endif
/*
* Allocation group filestream associations are tracked with per-ag atomic
* counters. These counters allow _xfs_filestream_pick_ag() to tell whether a
* particular AG already has active filestreams associated with it. The mount
* point's m_peraglock is used to protect these counters from per-ag array
* re-allocation during a growfs operation. When xfs_growfs_data_private() is
* about to reallocate the array, it calls xfs_filestream_flush() with the
* m_peraglock held in write mode.
*
* Since xfs_mru_cache_flush() guarantees that all the free functions for all
* the cache elements have finished executing before it returns, it's safe for
* the free functions to use the atomic counters without m_peraglock protection.
* This allows the implementation of xfs_fstrm_free_func() to be agnostic about
* whether it was called with the m_peraglock held in read mode, write mode or
* not held at all. The race condition this addresses is the following:
*
* - The work queue scheduler fires and pulls a filestream directory cache
* element off the LRU end of the cache for deletion, then gets pre-empted.
* - A growfs operation grabs the m_peraglock in write mode, flushes all the
* remaining items from the cache and reallocates the mount point's per-ag
* array, resetting all the counters to zero.
* - The work queue thread resumes and calls the free function for the element
* it started cleaning up earlier. In the process it decrements the
* filestreams counter for an AG that now has no references.
*
* With a shrinkfs feature, the above scenario could panic the system.
*
* All other uses of the following macros should be protected by either the
* m_peraglock held in read mode, or the cache's internal locking exposed by the
* interval between a call to xfs_mru_cache_lookup() and a call to
* xfs_mru_cache_done(). In addition, the m_peraglock must be held in read mode
* when new elements are added to the cache.
*
* Combined, these locking rules ensure that no associations will ever exist in
* the cache that reference per-ag array elements that have since been
* reallocated.
*/
/*
* xfs_filestream_peek_ag is only used in tracing code
*/
static inline int
xfs_filestream_peek_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ret;
pag = xfs_perag_get(mp, agno);
ret = atomic_read(&pag->pagf_fstrms);
xfs_perag_put(pag);
return ret;
}
static inline int
xfs_filestream_get_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ret;
pag = xfs_perag_get(mp, agno);
ret = atomic_inc_return(&pag->pagf_fstrms);
xfs_perag_put(pag);
return ret;
}
static inline int
xfs_filestream_put_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ret;
pag = xfs_perag_get(mp, agno);
ret = atomic_dec_return(&pag->pagf_fstrms);
xfs_perag_put(pag);
return ret;
}
/* allocation selection flags */
typedef enum xfs_fstrm_alloc {
XFS_PICK_USERDATA = 1,
XFS_PICK_LOWSPACE = 2,
} xfs_fstrm_alloc_t;
/* prototypes for filestream.c */
int xfs_filestream_init(void);
void xfs_filestream_uninit(void);
int xfs_filestream_mount(struct xfs_mount *mp);
void xfs_filestream_unmount(struct xfs_mount *mp);
xfs_agnumber_t xfs_filestream_lookup_ag(struct xfs_inode *ip);
int xfs_filestream_associate(struct xfs_inode *dip, struct xfs_inode *ip);
void xfs_filestream_deassociate(struct xfs_inode *ip);
int xfs_filestream_new_ag(struct xfs_bmalloca *ap, xfs_agnumber_t *agp);
/* filestreams for the inode? */
static inline int
xfs_inode_is_filestream(
struct xfs_inode *ip)
{
return (ip->i_mount->m_flags & XFS_MOUNT_FILESTREAMS) ||
xfs_iflags_test(ip, XFS_IFILESTREAM) ||
(ip->i_d.di_flags & XFS_DIFLAG_FILESTREAM);
}
#endif /* __KERNEL__ */
#endif /* __XFS_FILESTREAM_H__ */
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