[PATCH v4 0/6] speculative preallocation quota throttling

[PATCH v4 0/6] speculative preallocation quota throttling

[Brian Foster]

Hi all,

Here is v4 of the speculative preallocation quota throttling set. Patch 3 of v3
is dropped due to a redundancy and a few changes are made to the threshold
management code (patch 4/6). The remaining patches are unchanged from v3.

Brian

v4:
- Drop patch 3/7 from v3 (xfs: cap prealloc size to free space before shift).
- Several updates to patch 4/6:
  - Rename xfs_dquot_init_prealloc() to xfs_dquot_set_prealloc_limits().
  - Unroll the prealloc threshold loop and remove the increment def.
  - Fix up some comments.
v3:
- Rebased on top of updated speculative preallocation algorithm.
v2:
- Fix up xfs_iomap_prealloc_size() rounding (patch 2).
- Add pre-calculated fields to xfs_dquot to support throttling.
- Move to logarithmic (shift) throttler and finer tuned trigger/throttle logic.

Brian Foster (6):
  xfs: reorganize xfs_iomap_prealloc_size to remove indentation
  xfs: push rounddown_pow_of_two() to after prealloc throttle
  xfs: pass xfs_dquot to xfs_qm_adjust_dqlimits() instead of
    xfs_disk_dquot_t
  xfs: xfs_dquot prealloc throttling watermarks and low free space
  xfs: add quota-driven speculative preallocation throttling
  xfs: xfs_iomap_prealloc_size() tracepoint

 fs/xfs/xfs_dquot.c       |   44 ++++++++++++-
 fs/xfs/xfs_dquot.h       |   14 ++++-
 fs/xfs/xfs_iomap.c       |  161 +++++++++++++++++++++++++++++++++++++---------
 fs/xfs/xfs_qm.c          |    2 +-
 fs/xfs/xfs_qm_syscalls.c |    1 +
 fs/xfs/xfs_trace.h       |   24 +++++++
 fs/xfs/xfs_trans_dquot.c |    2 +-
 7 files changed, 212 insertions(+), 36 deletions(-)

-- 
1.7.7.6

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[PATCH v4 1/6] xfs: reorganize xfs_iomap_prealloc_size to remove indentation

[Brian Foster]

The majority of xfs_iomap_prealloc_size() executes within the
check for lack of default I/O size. Reverse the logic to remove the
extra indentation.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
---
 fs/xfs/xfs_iomap.c |   63 ++++++++++++++++++++++++++-------------------------
 1 files changed, 32 insertions(+), 31 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 912d83d..d914419 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -381,42 +381,43 @@ xfs_iomap_prealloc_size(
 	int			nimaps)
 {
 	xfs_fsblock_t		alloc_blocks = 0;
+	int			shift = 0;
+	int64_t			freesp;
 
 	alloc_blocks = xfs_iomap_eof_prealloc_initial_size(mp, ip, offset,
 							   imap, nimaps);
-	if (alloc_blocks > 0) {
-		int shift = 0;
-		int64_t freesp;
-
-		alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
-					rounddown_pow_of_two(alloc_blocks));
-
-		xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
-		freesp = mp->m_sb.sb_fdblocks;
-		if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
-			shift = 2;
-			if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
-				shift++;
-			if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
-				shift++;
-			if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
-				shift++;
-			if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
-				shift++;
-		}
-		if (shift)
-			alloc_blocks >>= shift;
-
-		/*
-		 * If we are still trying to allocate more space than is
-		 * available, squash the prealloc hard. This can happen if we
-		 * have a large file on a small filesystem and the above
-		 * lowspace thresholds are smaller than MAXEXTLEN.
-		 */
-		while (alloc_blocks >= freesp)
-			alloc_blocks >>= 4;
+	if (!alloc_blocks)
+		goto check_writeio;
+
+	alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
+				rounddown_pow_of_two(alloc_blocks));
+
+	xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
+	freesp = mp->m_sb.sb_fdblocks;
+	if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
+		shift = 2;
+		if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
+			shift++;
+		if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
+			shift++;
+		if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
+			shift++;
+		if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
+			shift++;
 	}
+	if (shift)
+		alloc_blocks >>= shift;
+
+	/*
+	 * If we are still trying to allocate more space than is
+	 * available, squash the prealloc hard. This can happen if we
+	 * have a large file on a small filesystem and the above
+	 * lowspace thresholds are smaller than MAXEXTLEN.
+	 */
+	while (alloc_blocks >= freesp)
+		alloc_blocks >>= 4;
 
+check_writeio:
 	if (alloc_blocks < mp->m_writeio_blocks)
 		alloc_blocks = mp->m_writeio_blocks;
 
-- 
1.7.7.6

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[PATCH v4 2/6] xfs: push rounddown_pow_of_two() to after prealloc throttle

[Brian Foster]

The round down occurs towards the beginning of the function. Push
it down after throttling has occurred. This is to support adding
further transformations to 'alloc_blocks' that might not preserve
power-of-two alignment (and thus could lead to rounding down
multiple times).

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
---
 fs/xfs/xfs_iomap.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index d914419..daa08f6 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -389,8 +389,15 @@ xfs_iomap_prealloc_size(
 	if (!alloc_blocks)
 		goto check_writeio;
 
-	alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
-				rounddown_pow_of_two(alloc_blocks));
+	/*
+	 * MAXEXTLEN is not a power of two value but we round the prealloc down
+	 * to the nearest power of two value after throttling. To prevent the
+	 * round down from unconditionally reducing the maximum supported prealloc
+	 * size, we round up first, apply appropriate throttling, round down and
+	 * cap the value to MAXEXTLEN.
+	 */
+	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
+				       alloc_blocks);
 
 	xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
 	freesp = mp->m_sb.sb_fdblocks;
@@ -407,6 +414,14 @@ xfs_iomap_prealloc_size(
 	}
 	if (shift)
 		alloc_blocks >>= shift;
+	/*
+	 * rounddown_pow_of_two() returns an undefined result if we pass in
+	 * alloc_blocks = 0.
+	 */
+	if (alloc_blocks)
+		alloc_blocks = rounddown_pow_of_two(alloc_blocks);
+	if (alloc_blocks > MAXEXTLEN)
+		alloc_blocks = MAXEXTLEN;
 
 	/*
 	 * If we are still trying to allocate more space than is
-- 
1.7.7.6

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[PATCH v4 3/6] xfs: pass xfs_dquot to xfs_qm_adjust_dqlimits() instead of xfs_disk_dquot_t

[Brian Foster]

Modify xfs_qm_adjust_dqlimits() to take the xfs_dquot as a
parameter instead of just the xfs_disk_dquot_t so we can update
in-memory fields if necessary.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_dquot.c       |    3 ++-
 fs/xfs/xfs_dquot.h       |    2 +-
 fs/xfs/xfs_qm.c          |    2 +-
 fs/xfs/xfs_trans_dquot.c |    2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index 8025eb2..e1833b9 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -86,9 +86,10 @@ xfs_qm_dqdestroy(
 void
 xfs_qm_adjust_dqlimits(
 	xfs_mount_t		*mp,
-	xfs_disk_dquot_t	*d)
+	struct xfs_dquot	*dq)
 {
 	xfs_quotainfo_t		*q = mp->m_quotainfo;
+	xfs_disk_dquot_t	*d = &dq->q_core;
 
 	ASSERT(d->d_id);
 
diff --git a/fs/xfs/xfs_dquot.h b/fs/xfs/xfs_dquot.h
index c694a84..69491b6 100644
--- a/fs/xfs/xfs_dquot.h
+++ b/fs/xfs/xfs_dquot.h
@@ -146,7 +146,7 @@ extern void		xfs_qm_dqunpin_wait(xfs_dquot_t *);
 extern void		xfs_qm_adjust_dqtimers(xfs_mount_t *,
 					xfs_disk_dquot_t *);
 extern void		xfs_qm_adjust_dqlimits(xfs_mount_t *,
-					xfs_disk_dquot_t *);
+					       struct xfs_dquot *);
 extern int		xfs_qm_dqget(xfs_mount_t *, xfs_inode_t *,
 					xfs_dqid_t, uint, uint, xfs_dquot_t **);
 extern void		xfs_qm_dqput(xfs_dquot_t *);
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index e5b5cf9..d0acb4e 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -1057,7 +1057,7 @@ xfs_qm_quotacheck_dqadjust(
 	 * There are no timers for the default values set in the root dquot.
 	 */
 	if (dqp->q_core.d_id) {
-		xfs_qm_adjust_dqlimits(mp, &dqp->q_core);
+		xfs_qm_adjust_dqlimits(mp, dqp);
 		xfs_qm_adjust_dqtimers(mp, &dqp->q_core);
 	}
 
diff --git a/fs/xfs/xfs_trans_dquot.c b/fs/xfs/xfs_trans_dquot.c
index 642c2d6..22d3da3 100644
--- a/fs/xfs/xfs_trans_dquot.c
+++ b/fs/xfs/xfs_trans_dquot.c
@@ -412,7 +412,7 @@ xfs_trans_apply_dquot_deltas(
 			 * Start/reset the timer(s) if needed.
 			 */
 			if (d->d_id) {
-				xfs_qm_adjust_dqlimits(tp->t_mountp, d);
+				xfs_qm_adjust_dqlimits(tp->t_mountp, dqp);
 				xfs_qm_adjust_dqtimers(tp->t_mountp, d);
 			}
 
-- 
1.7.7.6

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[PATCH v4 4/6] xfs: xfs_dquot prealloc throttling watermarks and low free space

[Brian Foster]

Enable tracking of high and low watermarks for preallocation
throttling of files under quota restrictions. These values are
calculated when the quota limit is read from disk or modified and
cached for later use by the throttling algorithm.

The high watermark specifies when preallocation is disabled, the
low watermark specifies when throttling is enabled and the low free
space data structure contains precalculated low free space limits
to serve as input to determine the level of throttling required.

Note that the low free space data structure is based on the
existing global low free space data structure with the exception of
using three stages (5%, 3% and 1%) rather than five to reduce the
impact of xfs_dquot memory overhead.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_dquot.c       |   41 +++++++++++++++++++++++++++++++++++++++--
 fs/xfs/xfs_dquot.h       |   12 ++++++++++++
 fs/xfs/xfs_qm_syscalls.c |    1 +
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index e1833b9..e3aa801 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -90,13 +90,18 @@ xfs_qm_adjust_dqlimits(
 {
 	xfs_quotainfo_t		*q = mp->m_quotainfo;
 	xfs_disk_dquot_t	*d = &dq->q_core;
+	int			prealloc = 0;
 
 	ASSERT(d->d_id);
 
-	if (q->qi_bsoftlimit && !d->d_blk_softlimit)
+	if (q->qi_bsoftlimit && !d->d_blk_softlimit) {
 		d->d_blk_softlimit = cpu_to_be64(q->qi_bsoftlimit);
-	if (q->qi_bhardlimit && !d->d_blk_hardlimit)
+		prealloc = 1;
+	}
+	if (q->qi_bhardlimit && !d->d_blk_hardlimit) {
 		d->d_blk_hardlimit = cpu_to_be64(q->qi_bhardlimit);
+		prealloc = 1;
+	}
 	if (q->qi_isoftlimit && !d->d_ino_softlimit)
 		d->d_ino_softlimit = cpu_to_be64(q->qi_isoftlimit);
 	if (q->qi_ihardlimit && !d->d_ino_hardlimit)
@@ -105,6 +110,9 @@ xfs_qm_adjust_dqlimits(
 		d->d_rtb_softlimit = cpu_to_be64(q->qi_rtbsoftlimit);
 	if (q->qi_rtbhardlimit && !d->d_rtb_hardlimit)
 		d->d_rtb_hardlimit = cpu_to_be64(q->qi_rtbhardlimit);
+
+	if (prealloc)
+		xfs_dquot_set_prealloc_limits(dq);
 }
 
 /*
@@ -249,6 +257,32 @@ xfs_qm_init_dquot_blk(
 	xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1);
 }
 
+/*
+ * Initialize the dynamic speculative preallocation thresholds. The lo/hi
+ * watermarks correspond to the soft and hard limits by default. If a soft limit
+ * is not specified, we use 95% of the hard limit.
+ */
+void
+xfs_dquot_set_prealloc_limits(struct xfs_dquot *dqp)
+{
+	__uint64_t space;
+
+	dqp->q_prealloc_hi_wmark = be64_to_cpu(dqp->q_core.d_blk_hardlimit);
+	dqp->q_prealloc_lo_wmark = be64_to_cpu(dqp->q_core.d_blk_softlimit);
+	if (!dqp->q_prealloc_lo_wmark) {
+		dqp->q_prealloc_lo_wmark = dqp->q_prealloc_hi_wmark;
+		do_div(dqp->q_prealloc_lo_wmark, 100);
+		dqp->q_prealloc_lo_wmark *= 95;
+	}
+
+	space = dqp->q_prealloc_hi_wmark;
+
+	do_div(space, 100);
+	dqp->q_low_space[XFS_QLOWSP_1_PCNT] = space;
+	dqp->q_low_space[XFS_QLOWSP_3_PCNT] = space * 3;
+	dqp->q_low_space[XFS_QLOWSP_5_PCNT] = space * 5;
+}
+
 static void
 xfs_dquot_buf_verify(
 	struct xfs_buf		*bp)
@@ -649,6 +683,9 @@ xfs_qm_dqread(
 	dqp->q_res_icount = be64_to_cpu(ddqp->d_icount);
 	dqp->q_res_rtbcount = be64_to_cpu(ddqp->d_rtbcount);
 
+	/* initialize the dquot speculative prealloc thresholds */
+	xfs_dquot_set_prealloc_limits(dqp);
+
 	/* Mark the buf so that this will stay incore a little longer */
 	xfs_buf_set_ref(bp, XFS_DQUOT_REF);
 
diff --git a/fs/xfs/xfs_dquot.h b/fs/xfs/xfs_dquot.h
index 69491b6..4263f33 100644
--- a/fs/xfs/xfs_dquot.h
+++ b/fs/xfs/xfs_dquot.h
@@ -32,6 +32,13 @@
 struct xfs_mount;
 struct xfs_trans;
 
+enum {
+	XFS_QLOWSP_1_PCNT = 0,
+	XFS_QLOWSP_3_PCNT,
+	XFS_QLOWSP_5_PCNT,
+	XFS_QLOWSP_MAX
+};
+
 /*
  * The incore dquot structure
  */
@@ -51,6 +58,9 @@ typedef struct xfs_dquot {
 	xfs_qcnt_t	 q_res_bcount;	/* total regular nblks used+reserved */
 	xfs_qcnt_t	 q_res_icount;	/* total inos allocd+reserved */
 	xfs_qcnt_t	 q_res_rtbcount;/* total realtime blks used+reserved */
+	xfs_qcnt_t	 q_prealloc_lo_wmark;/* prealloc throttle wmark */
+	xfs_qcnt_t	 q_prealloc_hi_wmark;/* prealloc disabled wmark */
+	int64_t		 q_low_space[XFS_QLOWSP_MAX];
 	struct mutex	 q_qlock;	/* quota lock */
 	struct completion q_flush;	/* flush completion queue */
 	atomic_t          q_pincount;	/* dquot pin count */
@@ -153,6 +163,8 @@ extern void		xfs_qm_dqput(xfs_dquot_t *);
 
 extern void		xfs_dqlock2(struct xfs_dquot *, struct xfs_dquot *);
 
+extern void		xfs_dquot_set_prealloc_limits(struct xfs_dquot *);
+
 static inline struct xfs_dquot *xfs_qm_dqhold(struct xfs_dquot *dqp)
 {
 	xfs_dqlock(dqp);
diff --git a/fs/xfs/xfs_qm_syscalls.c b/fs/xfs/xfs_qm_syscalls.c
index cf9a340..6096eed 100644
--- a/fs/xfs/xfs_qm_syscalls.c
+++ b/fs/xfs/xfs_qm_syscalls.c
@@ -529,6 +529,7 @@ xfs_qm_scall_setqlim(
 	if (hard == 0 || hard >= soft) {
 		ddq->d_blk_hardlimit = cpu_to_be64(hard);
 		ddq->d_blk_softlimit = cpu_to_be64(soft);
+		xfs_dquot_set_prealloc_limits(dqp);
 		if (id == 0) {
 			q->qi_bhardlimit = hard;
 			q->qi_bsoftlimit = soft;
-- 
1.7.7.6

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[PATCH v4 5/6] xfs: add quota-driven speculative preallocation throttling

[Brian Foster]

Introduce the need_throttle() and calc_throttle() functions to
independently check whether throttling is required for a particular
dquot and if so, calculate the associated throttling metrics based
on the state of the quota. We use the same general algorithm to
calculate the throttle shift as for global free space with the
exception of using three stages rather than five.

Update xfs_iomap_prealloc_size() to use the smallest available
prealloc size based on each of the constraints and apply the
maximum shift to obtain the throttled preallocation size.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_iomap.c |   82 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 82 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index daa08f6..34640a3f 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -42,6 +42,8 @@
 #include "xfs_iomap.h"
 #include "xfs_trace.h"
 #include "xfs_icache.h"
+#include "xfs_dquot_item.h"
+#include "xfs_dquot.h"
 
 
 #define XFS_WRITEIO_ALIGN(mp,off)	(((off) >> mp->m_writeio_log) \
@@ -366,6 +368,61 @@ xfs_iomap_eof_prealloc_initial_size(
 	return XFS_B_TO_FSB(mp, offset);
 }
 
+STATIC bool
+xfs_quota_need_throttle(
+	struct xfs_inode *ip,
+	int type,
+	xfs_fsblock_t alloc_blocks)
+{
+	struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
+
+	if (!dq || !xfs_this_quota_on(ip->i_mount, type))
+		return false;
+
+	/* no hi watermark, no throttle */
+	if (!dq->q_prealloc_hi_wmark)
+		return false;
+
+	/* under the lo watermark, no throttle */
+	if (dq->q_res_bcount + alloc_blocks < dq->q_prealloc_lo_wmark)
+		return false;
+
+	return true;
+}
+
+STATIC void
+xfs_quota_calc_throttle(
+	struct xfs_inode *ip,
+	int type,
+	xfs_fsblock_t *qblocks,
+	int *qshift)
+{
+	int64_t freesp;
+	int shift = 0;
+	struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
+
+	/* over hi wmark, squash the prealloc completely */
+	if (dq->q_res_bcount >= dq->q_prealloc_hi_wmark) {
+		*qblocks = 0;
+		return;
+	}
+
+	freesp = dq->q_prealloc_hi_wmark - dq->q_res_bcount;
+	if (freesp < dq->q_low_space[XFS_QLOWSP_5_PCNT]) {
+		shift = 2;
+		if (freesp < dq->q_low_space[XFS_QLOWSP_3_PCNT])
+			shift += 2;
+		if (freesp < dq->q_low_space[XFS_QLOWSP_1_PCNT])
+			shift += 2;
+	}
+
+	/* only overwrite the throttle values if we are more aggressive */
+	if ((freesp >> shift) < (*qblocks >> *qshift)) {
+		*qblocks = freesp;
+		*qshift = shift;
+	}
+}
+
 /*
  * If we don't have a user specified preallocation size, dynamically increase
  * the preallocation size as the size of the file grows. Cap the maximum size
@@ -383,11 +440,14 @@ xfs_iomap_prealloc_size(
 	xfs_fsblock_t		alloc_blocks = 0;
 	int			shift = 0;
 	int64_t			freesp;
+	xfs_fsblock_t		qblocks;
+	int			qshift = 0;
 
 	alloc_blocks = xfs_iomap_eof_prealloc_initial_size(mp, ip, offset,
 							   imap, nimaps);
 	if (!alloc_blocks)
 		goto check_writeio;
+	qblocks = alloc_blocks;
 
 	/*
 	 * MAXEXTLEN is not a power of two value but we round the prealloc down
@@ -412,6 +472,28 @@ xfs_iomap_prealloc_size(
 		if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
 			shift++;
 	}
+
+	/*
+	 * Check each quota to cap the prealloc size and provide a shift
+	 * value to throttle with.
+	 */
+	if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQ_USER, &qblocks, &qshift);
+	if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQ_GROUP, &qblocks, &qshift);
+	if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQ_PROJ, &qblocks, &qshift);
+
+	/*
+	 * The final prealloc size is set to the minimum of free space available
+	 * in each of the quotas and the overall filesystem.
+	 *
+	 * The shift throttle value is set to the maximum value as determined by
+	 * the global low free space values and per-quota low free space values.
+	 */
+	alloc_blocks = MIN(alloc_blocks, qblocks);
+	shift = MAX(shift, qshift);
+
 	if (shift)
 		alloc_blocks >>= shift;
 	/*
-- 
1.7.7.6

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[PATCH v4 6/6] xfs: xfs_iomap_prealloc_size() tracepoint

[Brian Foster]

Add a tracepoint to provide some feedback on preallocation size
calculation.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_iomap.c |    3 +++
 fs/xfs/xfs_trace.h |   24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 34640a3f..d5f800c 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -518,6 +518,9 @@ check_writeio:
 	if (alloc_blocks < mp->m_writeio_blocks)
 		alloc_blocks = mp->m_writeio_blocks;
 
+	trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
+				      mp->m_writeio_blocks);
+
 	return alloc_blocks;
 }
 
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 16a8129..aa4db33 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -619,6 +619,30 @@ DECLARE_EVENT_CLASS(xfs_iref_class,
 		  (char *)__entry->caller_ip)
 )
 
+TRACE_EVENT(xfs_iomap_prealloc_size,
+	TP_PROTO(struct xfs_inode *ip, xfs_fsblock_t blocks, int shift,
+		 unsigned int writeio_blocks),
+	TP_ARGS(ip, blocks, shift, writeio_blocks),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_ino_t, ino)
+		__field(xfs_fsblock_t, blocks)
+		__field(int, shift)
+		__field(unsigned int, writeio_blocks)
+	),
+	TP_fast_assign(
+		__entry->dev = VFS_I(ip)->i_sb->s_dev;
+		__entry->ino = ip->i_ino;
+		__entry->blocks = blocks;
+		__entry->shift = shift;
+		__entry->writeio_blocks = writeio_blocks;
+	),
+	TP_printk("dev %d:%d ino 0x%llx prealloc blocks %llu shift %d "
+		  "m_writeio_blocks %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino,
+		  __entry->blocks, __entry->shift, __entry->writeio_blocks)
+)
+
 #define DEFINE_IREF_EVENT(name) \
 DEFINE_EVENT(xfs_iref_class, name, \
 	TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip), \
-- 
1.7.7.6

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Re: [PATCH v4 1/6] xfs: reorganize xfs_iomap_prealloc_size to remove indentation

[Mark Tinguely]

On 02/20/13 09:10, Brian Foster wrote:
> The majority of xfs_iomap_prealloc_size() executes within the
> check for lack of default I/O size. Reverse the logic to remove the
> extra indentation.
>
> Signed-off-by: Brian Foster<bfoster@redhat.com>
> Reviewed-by: Dave Chinner<dchinner@redhat.com>
> Reviewed-by: Ben Myers<bpm@sgi.com>
> ---
>   fs/xfs/xfs_iomap.c |   63 ++++++++++++++++++++++++++-------------------------
>   1 files changed, 32 insertions(+), 31 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 912d83d..d914419 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -381,42 +381,43 @@ xfs_iomap_prealloc_size(
>   	int			nimaps)
>   {
>   	xfs_fsblock_t		alloc_blocks = 0;
> +	int			shift = 0;
> +	int64_t			freesp;

...

> +	freesp = mp->m_sb.sb_fdblocks;

...

> +	/*
> +	 * If we are still trying to allocate more space than is
> +	 * available, squash the prealloc hard. This can happen if we
> +	 * have a large file on a small filesystem and the above
> +	 * lowspace thresholds are smaller than MAXEXTLEN.
> +	 */
> +	while (alloc_blocks>= freesp)
> +		alloc_blocks>>= 4;


Hi Brian, I am looking at your speculative preallocation quota 
throttling series.

I know this code is from commit 4d559a3b. would this not be bad of 
freesp == 0?

--Mark.

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Re: [PATCH v4 1/6] xfs: reorganize xfs_iomap_prealloc_size to remove indentation

[Brian Foster]

On 02/22/2013 12:07 PM, Mark Tinguely wrote:
> On 02/20/13 09:10, Brian Foster wrote:
>> The majority of xfs_iomap_prealloc_size() executes within the
>> check for lack of default I/O size. Reverse the logic to remove the
>> extra indentation.
>>
>> Signed-off-by: Brian Foster<bfoster@redhat.com>
>> Reviewed-by: Dave Chinner<dchinner@redhat.com>
>> Reviewed-by: Ben Myers<bpm@sgi.com>
>> ---
>>   fs/xfs/xfs_iomap.c |   63
>> ++++++++++++++++++++++++++-------------------------
>>   1 files changed, 32 insertions(+), 31 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
>> index 912d83d..d914419 100644
>> --- a/fs/xfs/xfs_iomap.c
>> +++ b/fs/xfs/xfs_iomap.c
>> @@ -381,42 +381,43 @@ xfs_iomap_prealloc_size(
>>       int            nimaps)
>>   {
>>       xfs_fsblock_t        alloc_blocks = 0;
>> +    int            shift = 0;
>> +    int64_t            freesp;
> 
> ...
> 
>> +    freesp = mp->m_sb.sb_fdblocks;
> 
> ...
> 
>> +    /*
>> +     * If we are still trying to allocate more space than is
>> +     * available, squash the prealloc hard. This can happen if we
>> +     * have a large file on a small filesystem and the above
>> +     * lowspace thresholds are smaller than MAXEXTLEN.
>> +     */
>> +    while (alloc_blocks>= freesp)
>> +        alloc_blocks>>= 4;
> 
> 
> Hi Brian, I am looking at your speculative preallocation quota
> throttling series.
> 
> I know this code is from commit 4d559a3b. would this not be bad of
> freesp == 0?
> 

Thanks. Hmm, I guess if freesp is 0 we'd hit an infinite loop
(irrespective of this patchset). We could change the comparison to >,
but I think the following would be more clear:

	while (alloc_blocks && alloc_blocks >= freesp)
		alloc_blocks >>= 4;

Thoughts? I'll send out a one-liner to bat around if that looks
reasonable. Good catch.

Brian

> --Mark.
> 

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Re: [PATCH v4 1/6] xfs: reorganize xfs_iomap_prealloc_size to remove indentation

[Mark Tinguely]

On 02/22/13 12:08, Brian Foster wrote:
> On 02/22/2013 12:07 PM, Mark Tinguely wrote:
>> On 02/20/13 09:10, Brian Foster wrote:
>>> The majority of xfs_iomap_prealloc_size() executes within the
>>> check for lack of default I/O size. Reverse the logic to remove the
>>> extra indentation.
>>>
>>> Signed-off-by: Brian Foster<bfoster@redhat.com>
>>> Reviewed-by: Dave Chinner<dchinner@redhat.com>
>>> Reviewed-by: Ben Myers<bpm@sgi.com>
>>> ---
>>>    fs/xfs/xfs_iomap.c |   63
>>> ++++++++++++++++++++++++++-------------------------
>>>    1 files changed, 32 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
>>> index 912d83d..d914419 100644
>>> --- a/fs/xfs/xfs_iomap.c
>>> +++ b/fs/xfs/xfs_iomap.c
>>> @@ -381,42 +381,43 @@ xfs_iomap_prealloc_size(
>>>        int            nimaps)
>>>    {
>>>        xfs_fsblock_t        alloc_blocks = 0;
>>> +    int            shift = 0;
>>> +    int64_t            freesp;
>>
>> ...
>>
>>> +    freesp = mp->m_sb.sb_fdblocks;
>>
>> ...
>>
>>> +    /*
>>> +     * If we are still trying to allocate more space than is
>>> +     * available, squash the prealloc hard. This can happen if we
>>> +     * have a large file on a small filesystem and the above
>>> +     * lowspace thresholds are smaller than MAXEXTLEN.
>>> +     */
>>> +    while (alloc_blocks>= freesp)
>>> +        alloc_blocks>>= 4;
>>
>>
>> Hi Brian, I am looking at your speculative preallocation quota
>> throttling series.
>>
>> I know this code is from commit 4d559a3b. would this not be bad of
>> freesp == 0?
>>
>
> Thanks. Hmm, I guess if freesp is 0 we'd hit an infinite loop
> (irrespective of this patchset). We could change the comparison to>,
> but I think the following would be more clear:
>
> 	while (alloc_blocks&&  alloc_blocks>= freesp)
> 		alloc_blocks>>= 4;
>
> Thoughts? I'll send out a one-liner to bat around if that looks
> reasonable. Good catch.
>
> Brian
>
>> --Mark.


That looks reasonable to me.

Thanks,

--Mark.

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Re: [PATCH v4 0/6] speculative preallocation quota throttling

[Mark Tinguely]

On 02/20/13 09:10, Brian Foster wrote:
> Hi all,
>
> Here is v4 of the speculative preallocation quota throttling set. Patch 3 of v3
> is dropped due to a redundancy and a few changes are made to the threshold
> management code (patch 4/6). The remaining patches are unchanged from v3.
>
> Brian
>
> v4:
> - Drop patch 3/7 from v3 (xfs: cap prealloc size to free space before shift).
> - Several updates to patch 4/6:
>    - Rename xfs_dquot_init_prealloc() to xfs_dquot_set_prealloc_limits().
>    - Unroll the prealloc threshold loop and remove the increment def.
>    - Fix up some comments.
> v3:
> - Rebased on top of updated speculative preallocation algorithm.
> v2:
> - Fix up xfs_iomap_prealloc_size() rounding (patch 2).
> - Add pre-calculated fields to xfs_dquot to support throttling.
> - Move to logarithmic (shift) throttler and finer tuned trigger/throttle logic.
>
> Brian Foster (6):
>    xfs: reorganize xfs_iomap_prealloc_size to remove indentation
>    xfs: push rounddown_pow_of_two() to after prealloc throttle
>    xfs: pass xfs_dquot to xfs_qm_adjust_dqlimits() instead of
>      xfs_disk_dquot_t
>    xfs: xfs_dquot prealloc throttling watermarks and low free space
>    xfs: add quota-driven speculative preallocation throttling
>    xfs: xfs_iomap_prealloc_size() tracepoint
>
>   fs/xfs/xfs_dquot.c       |   44 ++++++++++++-
>   fs/xfs/xfs_dquot.h       |   14 ++++-
>   fs/xfs/xfs_iomap.c       |  161 +++++++++++++++++++++++++++++++++++++---------
>   fs/xfs/xfs_qm.c          |    2 +-
>   fs/xfs/xfs_qm_syscalls.c |    1 +
>   fs/xfs/xfs_trace.h       |   24 +++++++
>   fs/xfs/xfs_trans_dquot.c |    2 +-
>   7 files changed, 212 insertions(+), 36 deletions(-)
>

The rest of the series looks good to me. Consider it Review-by: me.

The tracing in patch 6 says how much, but not why, BUT I think the why
would require multiple tracepoints, so I okay with it.

	-- since I am being a grouch ... ---
I wish I had caught in the review for commit a1e16c26 that 
xfs_iomap_eof_prealloc_initial_size() is returning an int rather than 
xfs_fsblock_t for consistency.

--Mark.

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Re: [PATCH v4 0/6] speculative preallocation quota throttling

[Dave Chinner]

On Fri, Feb 22, 2013 at 02:09:04PM -0600, Mark Tinguely wrote:
> 
> 	-- since I am being a grouch ... ---
> I wish I had caught in the review for commit a1e16c26 that
> xfs_iomap_eof_prealloc_initial_size() is returning an int rather
> than xfs_fsblock_t for consistency.

Which is a bug, not an inconsistency. It means that alloc_blocks may
not return the right thing at the 2^31/2^32 FSB boundary.

Don't grouch like you can't possibly fix it, just send a patch. :P
The code isn't upstream yet, so we've got the entire 3.9-rc cycle to
fix it... :)

Cheers,

Dave.
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Re: [PATCH v4 0/6] speculative preallocation quota throttling

[Brian Foster]

[CC list]

On 02/25/2013 03:26 PM, Mark Tinguely wrote:
> On 02/20/13 09:10, Brian Foster wrote:
>> Hi all,
>>
>> Here is v4 of the speculative preallocation quota throttling set.
>> Patch 3 of v3
>> is dropped due to a redundancy and a few changes are made to the
>> threshold
>> management code (patch 4/6). The remaining patches are unchanged from v3.
>>
>> Brian
>>
...
>>
> 
> Since you are doing a v5 repost, you can clean up the typedefs in the
> routines that you touch:
> 

Sure, I'll make a pass through the set for such clean ups.

Brian

> For example in patch 3:
> 
> 
>         xfs_quotainfo_t         *q = mp->m_quotainfo;
> +       xfs_disk_dquot_t        *d = &dq->q_core;
>         ^^^^^^^^^
>     struct xfs_disk_dquot    d = &dq->q_core;
> ---
> patch 4:
> 
> xfs_disk_dquot_t
> 
>         xfs_quotainfo_t         *q = mp->m_quotainfo;
>         xfs_disk_dquot_t        *d = &dq->q_core;
> +       int                     prealloc = 0;
> 
> clean up the xfs_quotainfo_t and xfs_disk_dquot_t
> 
> --Mark.
> 

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Re: [PATCH v4 5/6] xfs: add quota-driven speculative preallocation throttling

[Mark Tinguely]

On 02/20/13 09:10, Brian Foster wrote:
> Introduce the need_throttle() and calc_throttle() functions to
> independently check whether throttling is required for a particular
> dquot and if so, calculate the associated throttling metrics based
> on the state of the quota. We use the same general algorithm to
> calculate the throttle shift as for global free space with the
> exception of using three stages rather than five.
>
> Update xfs_iomap_prealloc_size() to use the smallest available
> prealloc size based on each of the constraints and apply the
> maximum shift to obtain the throttled preallocation size.
>
> Signed-off-by: Brian Foster<bfoster@redhat.com>
> ---

>   	/*
>   	 * MAXEXTLEN is not a power of two value but we round the prealloc down
> @@ -412,6 +472,28 @@ xfs_iomap_prealloc_size(
>   		if (freesp<  mp->m_low_space[XFS_LOWSP_1_PCNT])
>   			shift++;
>   	}
> +
> +	/*
> +	 * Check each quota to cap the prealloc size and provide a shift
> +	 * value to throttle with.
> +	 */
> +	if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
> +		xfs_quota_calc_throttle(ip, XFS_DQ_USER,&qblocks,&qshift);
> +	if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
> +		xfs_quota_calc_throttle(ip, XFS_DQ_GROUP,&qblocks,&qshift);
> +	if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
> +		xfs_quota_calc_throttle(ip, XFS_DQ_PROJ,&qblocks,&qshift);
> +
> +	/*
> +	 * The final prealloc size is set to the minimum of free space available
> +	 * in each of the quotas and the overall filesystem.
> +	 *
> +	 * The shift throttle value is set to the maximum value as determined by
> +	 * the global low free space values and per-quota low free space values.
> +	 */
> +	alloc_blocks = MIN(alloc_blocks, qblocks);
> +	shift = MAX(shift, qshift);
> +
>   	if (shift)
>   		alloc_blocks>>= shift;
>   	/*

All the limits are applied from previous extents, quota and then the 
code from commit 055388a3 is applied:
	if (alloc_blocks < mp->m_writeio_blocks)
		alloc_blocks = mp->m_writeio_blocks;

                        ^^^^
we may not have mp->m_writeio_blocks left in the filesytem.
Doesn't the following make more sense?:

	if (alloc_blocks < mp->m_writeio_blocks)
		alloc_blocks = 0;

Thank-you,

--Mark

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Re: [PATCH v4 5/6] xfs: add quota-driven speculative preallocation throttling

[Dave Chinner]

On Mon, Feb 25, 2013 at 03:44:10PM -0600, Mark Tinguely wrote:
> On 02/20/13 09:10, Brian Foster wrote:
> >Introduce the need_throttle() and calc_throttle() functions to
> >independently check whether throttling is required for a particular
> >dquot and if so, calculate the associated throttling metrics based
> >on the state of the quota. We use the same general algorithm to
> >calculate the throttle shift as for global free space with the
> >exception of using three stages rather than five.
> >
> >Update xfs_iomap_prealloc_size() to use the smallest available
> >prealloc size based on each of the constraints and apply the
> >maximum shift to obtain the throttled preallocation size.
> >
> >Signed-off-by: Brian Foster<bfoster@redhat.com>
> >---
> 
> >  	/*
> >  	 * MAXEXTLEN is not a power of two value but we round the prealloc down
> >@@ -412,6 +472,28 @@ xfs_iomap_prealloc_size(
> >  		if (freesp<  mp->m_low_space[XFS_LOWSP_1_PCNT])
> >  			shift++;
> >  	}
> >+
> >+	/*
> >+	 * Check each quota to cap the prealloc size and provide a shift
> >+	 * value to throttle with.
> >+	 */
> >+	if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
> >+		xfs_quota_calc_throttle(ip, XFS_DQ_USER,&qblocks,&qshift);
> >+	if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
> >+		xfs_quota_calc_throttle(ip, XFS_DQ_GROUP,&qblocks,&qshift);
> >+	if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
> >+		xfs_quota_calc_throttle(ip, XFS_DQ_PROJ,&qblocks,&qshift);
> >+
> >+	/*
> >+	 * The final prealloc size is set to the minimum of free space available
> >+	 * in each of the quotas and the overall filesystem.
> >+	 *
> >+	 * The shift throttle value is set to the maximum value as determined by
> >+	 * the global low free space values and per-quota low free space values.
> >+	 */
> >+	alloc_blocks = MIN(alloc_blocks, qblocks);
> >+	shift = MAX(shift, qshift);
> >+
> >  	if (shift)
> >  		alloc_blocks>>= shift;
> >  	/*
> 
> All the limits are applied from previous extents, quota and then the
> code from commit 055388a3 is applied:
> 	if (alloc_blocks < mp->m_writeio_blocks)
> 		alloc_blocks = mp->m_writeio_blocks;
> 
>                        ^^^^
> we may not have mp->m_writeio_blocks left in the filesytem.
> Doesn't the following make more sense?:
> 
> 	if (alloc_blocks < mp->m_writeio_blocks)
> 		alloc_blocks = 0;

No. This is for prealloc, and we alwys try to prealloc the minimum
configured. If we can't prealloc that amount, then preallocation
fails and we'll try a single block.

Remember, the freesp calculation is done unlocked and hence freesp
is only an estimate. It may change between the reading of it and the
actual allocation attempt, and so the only real determination of
ENOSPC is the failure ot the allocation attempt.....

Cheers,

Dave.
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Re: [PATCH v4 5/6] xfs: add quota-driven speculative preallocation throttling

[Mark Tinguely]

On 02/25/13 16:14, Dave Chinner wrote:
> On Mon, Feb 25, 2013 at 03:44:10PM -0600, Mark Tinguely wrote:
>> On 02/20/13 09:10, Brian Foster wrote:
>>> Introduce the need_throttle() and calc_throttle() functions to
>>> independently check whether throttling is required for a particular
>>> dquot and if so, calculate the associated throttling metrics based
>>> on the state of the quota. We use the same general algorithm to
>>> calculate the throttle shift as for global free space with the
>>> exception of using three stages rather than five.
>>>
>>> Update xfs_iomap_prealloc_size() to use the smallest available
>>> prealloc size based on each of the constraints and apply the
>>> maximum shift to obtain the throttled preallocation size.
>>>
>>> Signed-off-by: Brian Foster<bfoster@redhat.com>
>>> ---
>>
>>>   	/*
>>>   	 * MAXEXTLEN is not a power of two value but we round the prealloc down
>>> @@ -412,6 +472,28 @@ xfs_iomap_prealloc_size(
>>>   		if (freesp<   mp->m_low_space[XFS_LOWSP_1_PCNT])
>>>   			shift++;
>>>   	}
>>> +
>>> +	/*
>>> +	 * Check each quota to cap the prealloc size and provide a shift
>>> +	 * value to throttle with.
>>> +	 */
>>> +	if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
>>> +		xfs_quota_calc_throttle(ip, XFS_DQ_USER,&qblocks,&qshift);
>>> +	if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
>>> +		xfs_quota_calc_throttle(ip, XFS_DQ_GROUP,&qblocks,&qshift);
>>> +	if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
>>> +		xfs_quota_calc_throttle(ip, XFS_DQ_PROJ,&qblocks,&qshift);
>>> +
>>> +	/*
>>> +	 * The final prealloc size is set to the minimum of free space available
>>> +	 * in each of the quotas and the overall filesystem.
>>> +	 *
>>> +	 * The shift throttle value is set to the maximum value as determined by
>>> +	 * the global low free space values and per-quota low free space values.
>>> +	 */
>>> +	alloc_blocks = MIN(alloc_blocks, qblocks);
>>> +	shift = MAX(shift, qshift);
>>> +
>>>   	if (shift)
>>>   		alloc_blocks>>= shift;
>>>   	/*
>>
>> All the limits are applied from previous extents, quota and then the
>> code from commit 055388a3 is applied:
>> 	if (alloc_blocks<  mp->m_writeio_blocks)
>> 		alloc_blocks = mp->m_writeio_blocks;
>>
>>                         ^^^^
>> we may not have mp->m_writeio_blocks left in the filesytem.
>> Doesn't the following make more sense?:
>>
>> 	if (alloc_blocks<  mp->m_writeio_blocks)
>> 		alloc_blocks = 0;
>
> No. This is for prealloc, and we alwys try to prealloc the minimum
> configured. If we can't prealloc that amount, then preallocation
> fails and we'll try a single block.
>
> Remember, the freesp calculation is done unlocked and hence freesp
> is only an estimate. It may change between the reading of it and the
> actual allocation attempt, and so the only real determination of
> ENOSPC is the failure ot the allocation attempt.....
>
> Cheers,
>
> Dave.

Thank-you for the information.

And without the minimum, it will immediately trip the assert:

Assertion failed: last_fsb > offset_fsb, file: 
/root/xfs/fs/xfs/xfs_iomap.c, line: 590

Sorry for the noise.

--Mark.


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