Commit 0664ce8d authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Alex Elder
Browse files

xfs: clean up filestreams helpers 



Move xfs_filestream_peek_ag, xxfs_filestream_get_ag and xfs_filestream_put_ag
from xfs_filestream.h to xfs_filestream.c where it's only callers are, and
remove the inline marker while we're at it to let the compiler decide on the
inlining.  Also don't return a value from xfs_filestream_put_ag because
we don't need it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent 73523a2e

fs/xfs/xfs_filestream.c

+77 −3
Original line number Diff line number Diff line
@@ -123,6 +123,82 @@ typedef struct fstrm_item 
	xfs_inode_t	*pip;	/* Parent directory inode pointer. */

} fstrm_item_t;



/*

 * 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.

 */

static 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 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 void

xfs_filestream_put_ag(

	xfs_mount_t	*mp,

	xfs_agnumber_t	agno)

{

	struct xfs_perag *pag;



	pag = xfs_perag_get(mp, agno);

	atomic_dec(&pag->pagf_fstrms);

	xfs_perag_put(pag);

}



/*

 * Scan the AGs starting at startag looking for an AG that isn't in use and has
@@ -351,16 +427,14 @@ xfs_fstrm_free_func( 
{

	fstrm_item_t	*item  = (fstrm_item_t *)data;

	xfs_inode_t	*ip = item->ip;

	int ref;



	ASSERT(ip->i_ino == ino);



	xfs_iflags_clear(ip, XFS_IFILESTREAM);



	/* Drop the reference taken on the AG when the item was added. */

	ref = xfs_filestream_put_ag(ip->i_mount, item->ag);

	xfs_filestream_put_ag(ip->i_mount, item->ag);



	ASSERT(ref >= 0);

	TRACE_FREE(ip->i_mount, ip, item->pip, item->ag,

		xfs_filestream_peek_ag(ip->i_mount, item->ag));

fs/xfs/xfs_filestream.h

+0 −82
Original line number Diff line number Diff line
@@ -42,88 +42,6 @@ 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,

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