xfs: consolidate xfs_inumbers

From: Jie Liu <[email protected]>

To fetch the file system number tables, we currently just ignore the errors and proceed to loop over the next AG or bump agino to the next chunk in case of btree operations failed, that is not properly because those errors might hint us potential file system problems.

This patch rework xfs_inumbers() to handle the btree operation errors as well as the loop conditions. Also, add pre-checkups for the given inode, we can save alloc/free the format buffer once against an invalid inode number.

Signed-off-by Jie Liu <[email protected]>

---
 fs/xfs/xfs_itable.c | 163 +++++++++++++++++++++++-----------------------------
 1 file changed, 72 insertions(+), 91 deletions(-)

fs/xfs/xfs_itable.c +29 -58

index 692671c..4d262f6 100644
@@ -558,12 +558,12 @@ xfs_bulkstat_single(
 int
 xfs_inumbers_fmt(
 	void			__user *ubuffer, /* buffer to write to */
-	const xfs_inogrp_t	*buffer,	/* buffer to read from */
+	const struct xfs_inogrp	*buffer,	/* buffer to read from */
 	long			count,		/* # of elements to read */
 	long			*written)	/* # of bytes written */
 {
 	if (copy_to_user(ubuffer, buffer, count * sizeof(*buffer)))
-		return -EFAULT;
+		return XFS_ERROR(EFAULT);
 	*written = count * sizeof(*buffer);
 	return 0;
 }

@@ -573,121 +573,102 @@ xfs_inumbers_fmt(
  */
 int					/* error status */
 xfs_inumbers(
-	xfs_mount_t	*mp,		/* mount point for filesystem */
-	xfs_ino_t	*lastino,	/* last inode returned */
-	int		*count,		/* size of buffer/count returned */
-	void		__user *ubuffer,/* buffer with inode descriptions */
-	inumbers_fmt_pf	formatter)
+	struct xfs_mount	*mp,/* mount point for filesystem */
+	xfs_ino_t		*lastino,/* last inode returned */
+	int			*count,/* size of buffer/count returned */
+	void			__user *ubuffer,/* buffer with inode desc */
+	inumbers_fmt_pf		formatter)
 {
-	xfs_buf_t	*agbp;
-	xfs_agino_t	agino;
-	xfs_agnumber_t	agno;
-	int		bcount;
-	xfs_inogrp_t	*buffer;
-	int		bufidx;
-	xfs_btree_cur_t	*cur;
-	int		error;
-	xfs_inobt_rec_incore_t r;
-	int		i;
-	xfs_ino_t	ino;
-	int		left;
-	int		tmp;
-
-	ino = (xfs_ino_t)*lastino;
-	agno = XFS_INO_TO_AGNO(mp, ino);
-	agino = XFS_INO_TO_AGINO(mp, ino);
-	left = *count;
+	xfs_agnumber_t		agno = XFS_INO_TO_AGNO(mp, *lastino);
+	xfs_agino_t		agino = XFS_INO_TO_AGINO(mp, *lastino);
+	int			left = *count;
+	struct xfs_btree_cur	*cur = NULL;
+	struct xfs_buf		*agbp = NULL;
+	struct xfs_inogrp	*buffer;
+	int			bcount;
+	int			bufidx;
+	int			error;
+
 	*count = 0;
+	if (agno >= mp->m_sb.sb_agcount ||
+	    *lastino != XFS_AGINO_TO_INO(mp, agno, agino))
+		return 0;
+
 	bcount = MIN(left, (int)(PAGE_SIZE / sizeof(*buffer)));
 	buffer = kmem_alloc(bcount * sizeof(*buffer), KM_SLEEP);
-	error = bufidx = 0;
-	cur = NULL;
-	agbp = NULL;
-	while (left > 0 && agno < mp->m_sb.sb_agcount) {
-		if (agbp == NULL) {
+	bufidx = error = 0;
+	do {
+		struct xfs_inobt_rec_incore	r;
+		int				stat;
+
+		if (!agbp) {
 			error = xfs_ialloc_read_agi(mp, NULL, agno, &agbp);
-			if (error) {
-				/*
-				 * If we can't read the AGI of this ag,
-				 * then just skip to the next one.
-				 */
-				ASSERT(cur == NULL);
-				agbp = NULL;
-				agno++;
-				agino = 0;
-				continue;
-			}
+			if (error)
+				break;
 			cur = xfs_inobt_init_cursor(mp, NULL, agbp, agno);
-			error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_GE,
-						 &tmp);
-			if (error) {
-				xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-				cur = NULL;
-				xfs_buf_relse(agbp);
-				agbp = NULL;
-				/*
-				 * Move up the last inode in the current
-				 * chunk.  The lookup_ge will always get
-				 * us the first inode in the next chunk.
-				 */
-				agino += XFS_INODES_PER_CHUNK - 1;
-				continue;
-			}
 		}
-		error = xfs_inobt_get_rec(cur, &r, &i);
-		if (error || i == 0) {

fs/xfs/xfs_itable.c +17 -21

+		if (!stat) {
+			/* Done, proceed to look up the next AG */
+			goto next_ag;
 		}
+
+		error = xfs_inobt_get_rec(cur, &r, &stat);
+		if (error)
+			break;
+		XFS_WANT_CORRUPTED_GOTO(stat == 1, error0);
+
 		agino = r.ir_startino + XFS_INODES_PER_CHUNK - 1;
 		buffer[bufidx].xi_startino =
 			XFS_AGINO_TO_INO(mp, agno, r.ir_startino);
 		buffer[bufidx].xi_alloccount =
 			XFS_INODES_PER_CHUNK - r.ir_freecount;
 		buffer[bufidx].xi_allocmask = ~r.ir_free;
-		bufidx++;
-		left--;
-		if (bufidx == bcount) {
-			long written;
-			if (formatter(ubuffer, buffer, bufidx, &written)) {
-				error = XFS_ERROR(EFAULT);
+		if (++bufidx == bcount) {
+			long	written;
+			error = formatter(ubuffer, buffer, bufidx, &written);
+			if (error)
 				break;
-			}
 			ubuffer += written;
 			*count += bufidx;
 			bufidx = 0;
 		}
-		if (left) {
-			error = xfs_btree_increment(cur, 0, &tmp);
-			if (error) {
-				xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-				cur = NULL;
-				xfs_buf_relse(agbp);
-				agbp = NULL;
-				/*
-				 * The agino value has already been bumped.
-				 * Just try to skip up to it.
-				 */
-				agino += XFS_INODES_PER_CHUNK;
-				continue;
-			}
+		if (!--left)
+			break;
+
+		error = xfs_btree_increment(cur, 0, &stat);

fs/xfs/xfs_itable.c +2 -4

 	if (!error) {
 		if (bufidx) {
-			long written;
-			if (formatter(ubuffer, buffer, bufidx, &written))
-				error = XFS_ERROR(EFAULT);
-			else
+			long	written;
+			error = formatter(ubuffer, buffer, bufidx, &written);

Quoted 136 lines · Jeff Liu

From: Jie Liu <[email protected]>

To fetch the file system number tables, we currently just ignore the errors and proceed to loop over the next AG or bump agino to the next chunk in case of btree operations failed, that is not properly because those errors might hint us potential file system problems.

This patch rework xfs_inumbers() to handle the btree operation errors as well as the loop conditions. Also, add pre-checkups for the given inode, we can save alloc/free the format buffer once against an invalid inode number.

Signed-off-by Jie Liu <[email protected]>

---
 fs/xfs/xfs_itable.c | 163 +++++++++++++++++++++++-----------------------------
 1 file changed, 72 insertions(+), 91 deletions(-)

fs/xfs/xfs_itable.c +29 -64

index 692671c..4d262f6 100644
@@ -558,12 +558,12 @@ xfs_bulkstat_single(
 int
 xfs_inumbers_fmt(
 	void			__user *ubuffer, /* buffer to write to */
-	const xfs_inogrp_t	*buffer,	/* buffer to read from */
+	const struct xfs_inogrp	*buffer,	/* buffer to read from */
 	long			count,		/* # of elements to read */
 	long			*written)	/* # of bytes written */
 {
 	if (copy_to_user(ubuffer, buffer, count * sizeof(*buffer)))
-		return -EFAULT;
+		return XFS_ERROR(EFAULT);
 	*written = count * sizeof(*buffer);
 	return 0;
 }

@@ -573,121 +573,102 @@ xfs_inumbers_fmt(
  */
 int					/* error status */
 xfs_inumbers(
-	xfs_mount_t	*mp,		/* mount point for filesystem */
-	xfs_ino_t	*lastino,	/* last inode returned */
-	int		*count,		/* size of buffer/count returned */
-	void		__user *ubuffer,/* buffer with inode descriptions */
-	inumbers_fmt_pf	formatter)
+	struct xfs_mount	*mp,/* mount point for filesystem */
+	xfs_ino_t		*lastino,/* last inode returned */
+	int			*count,/* size of buffer/count returned */
+	void			__user *ubuffer,/* buffer with inode desc */
+	inumbers_fmt_pf		formatter)
 {
-	xfs_buf_t	*agbp;
-	xfs_agino_t	agino;
-	xfs_agnumber_t	agno;
-	int		bcount;
-	xfs_inogrp_t	*buffer;
-	int		bufidx;
-	xfs_btree_cur_t	*cur;
-	int		error;
-	xfs_inobt_rec_incore_t r;
-	int		i;
-	xfs_ino_t	ino;
-	int		left;
-	int		tmp;
-
-	ino = (xfs_ino_t)*lastino;
-	agno = XFS_INO_TO_AGNO(mp, ino);
-	agino = XFS_INO_TO_AGINO(mp, ino);
-	left = *count;
+	xfs_agnumber_t		agno = XFS_INO_TO_AGNO(mp, *lastino);
+	xfs_agino_t		agino = XFS_INO_TO_AGINO(mp, *lastino);
+	int			left = *count;
+	struct xfs_btree_cur	*cur = NULL;
+	struct xfs_buf		*agbp = NULL;
+	struct xfs_inogrp	*buffer;
+	int			bcount;
+	int			bufidx;
+	int			error;
+
 	*count = 0;
+	if (agno >= mp->m_sb.sb_agcount ||
+	    *lastino != XFS_AGINO_TO_INO(mp, agno, agino))
+		return 0;
+
 	bcount = MIN(left, (int)(PAGE_SIZE / sizeof(*buffer)));
 	buffer = kmem_alloc(bcount * sizeof(*buffer), KM_SLEEP);
-	error = bufidx = 0;
-	cur = NULL;
-	agbp = NULL;
-	while (left > 0 && agno < mp->m_sb.sb_agcount) {
-		if (agbp == NULL) {
+	bufidx = error = 0;
+	do {
+		struct xfs_inobt_rec_incore	r;
+		int				stat;
+
+		if (!agbp) {
 			error = xfs_ialloc_read_agi(mp, NULL, agno, &agbp);
-			if (error) {
-				/*
-				 * If we can't read the AGI of this ag,
-				 * then just skip to the next one.
-				 */
-				ASSERT(cur == NULL);
-				agbp = NULL;
-				agno++;
-				agino = 0;
-				continue;
-			}
+			if (error)
+				break;
 			cur = xfs_inobt_init_cursor(mp, NULL, agbp, agno);
-			error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_GE,
-						 &tmp);
-			if (error) {
-				xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-				cur = NULL;
-				xfs_buf_relse(agbp);
-				agbp = NULL;
-				/*
-				 * Move up the last inode in the current
-				 * chunk.  The lookup_ge will always get
-				 * us the first inode in the next chunk.
-				 */
-				agino += XFS_INODES_PER_CHUNK - 1;
-				continue;
-			}
 		}
-		error = xfs_inobt_get_rec(cur, &r, &i);
-		if (error || i == 0) {
-			xfs_buf_relse(agbp);
-			agbp = NULL;
-			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
-			cur = NULL;
-			agno++;
-			agino = 0;

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 612

Quoted 4 lines

fs/xfs/xfs_itable.c +3 -1

-			continue;
+		error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_GE, &stat);
+		if (error)
+			break;

Isn't this lookup only needed after cursor initialization? i.e., we lookup once and increment through the records via xfs_btree_increment() below.

Quoted 59 lines

fs/xfs/xfs_itable.c +25 -21

+		if (!stat) {
+			/* Done, proceed to look up the next AG */
+			goto next_ag;
 		}
+
+		error = xfs_inobt_get_rec(cur, &r, &stat);
+		if (error)
+			break;
+		XFS_WANT_CORRUPTED_GOTO(stat == 1, error0);
+
 		agino = r.ir_startino + XFS_INODES_PER_CHUNK - 1;
 		buffer[bufidx].xi_startino =
 			XFS_AGINO_TO_INO(mp, agno, r.ir_startino);
 		buffer[bufidx].xi_alloccount =
 			XFS_INODES_PER_CHUNK - r.ir_freecount;
 		buffer[bufidx].xi_allocmask = ~r.ir_free;
-		bufidx++;
-		left--;
-		if (bufidx == bcount) {
-			long written;
-			if (formatter(ubuffer, buffer, bufidx, &written)) {
-				error = XFS_ERROR(EFAULT);
+		if (++bufidx == bcount) {
+			long	written;
+			error = formatter(ubuffer, buffer, bufidx, &written);
+			if (error)
 				break;
-			}
 			ubuffer += written;
 			*count += bufidx;
 			bufidx = 0;
 		}
-		if (left) {
-			error = xfs_btree_increment(cur, 0, &tmp);
-			if (error) {
-				xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-				cur = NULL;
-				xfs_buf_relse(agbp);
-				agbp = NULL;
-				/*
-				 * The agino value has already been bumped.
-				 * Just try to skip up to it.
-				 */
-				agino += XFS_INODES_PER_CHUNK;
-				continue;
-			}
+		if (!--left)
+			break;
+
+		error = xfs_btree_increment(cur, 0, &stat);
+		if (error)
+			break;
+		if (stat) {
+			/*
+			 * The agino value has already been bumped, just try
+			 * to skip up to it.
+			 */
+			agino += XFS_INODES_PER_CHUNK;

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 651

Quoted 2 lines

fs/xfs/xfs_itable.c +1 -0

+			continue;
 		}

Maybe it's just me, but this reads a little funny to me. In particular because we only get here if stat == 1. I wonder if this would look a bit cleaner if we pulled the next_ag labeled block below up into the goto, since that appears to be the only reference. Then just let the loop fall through.

Also, I think the agino addition here becomes unnecessary when the lookup issue above is addressed.

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 660

Quoted 10 lines

fs/xfs/xfs_itable.c +9 -1

-	}
+
+next_ag:
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+		xfs_buf_relse(agbp);
+		agbp = NULL;
+		agino = 0;
+	} while (++agno < mp->m_sb.sb_agcount);
+

... and just thinking about the logic that way highlights the bug here, where we bump agno due to the continue above (where IIUC, we intend to only move forward within the ag). Perhaps the ++agno should be part of the broken off 'next_ag' logic as well.

Quoted 22 lines · Brian Foster

Quoted 21 lines · Jeff Liu

From: Jie Liu <[email protected]>

To fetch the file system number tables, we currently just ignore the errors and proceed to loop over the next AG or bump agino to the next chunk in case of btree operations failed, that is not properly because those errors might hint us potential file system problems.

This patch rework xfs_inumbers() to handle the btree operation errors as well as the loop conditions. Also, add pre-checkups for the given inode, we can save alloc/free the format buffer once against an invalid inode number.

Signed-off-by Jie Liu <[email protected]>

---
 fs/xfs/xfs_itable.c | 163 +++++++++++++++++++++++-----------------------------
 1 file changed, 72 insertions(+), 91 deletions(-)

fs/xfs/xfs_itable.c +0 -0

index 692671c..4d262f6 100644

Quoted 8 lines

Quoted 8 lines

fs/xfs/xfs_itable.c +0 -8

-		error = xfs_inobt_get_rec(cur, &r, &i);
-		if (error || i == 0) {
-			xfs_buf_relse(agbp);
-			agbp = NULL;
-			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
-			cur = NULL;
-			agno++;
-			agino = 0;

Quoted 8 lines

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 612

Quoted 4 lines

fs/xfs/xfs_itable.c +3 -1

-			continue;
+		error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_GE, &stat);
+		if (error)
+			break;

Isn't this lookup only needed after cursor initialization? i.e., we lookup once and increment through the records via xfs_btree_increment() below.

Yes, but please see my comments below.

Quoted 1 line

Quoted 12 lines

Quoted 12 lines

fs/xfs/xfs_itable.c +12 -0

+		if (!--left)
+			break;
+
+		error = xfs_btree_increment(cur, 0, &stat);
+		if (error)
+			break;
+		if (stat) {
+			/*
+			 * The agino value has already been bumped, just try
+			 * to skip up to it.
+			 */
+			agino += XFS_INODES_PER_CHUNK;

Quoted 8 lines

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 651

Quoted 2 lines

fs/xfs/xfs_itable.c +1 -0

+			continue;
 		}

Maybe it's just me, but this reads a little funny to me. In particular because we only get here if stat == 1. I wonder if this would look a bit cleaner if we pulled the next_ag labeled block below up into the goto, since that appears to be the only reference. Then just let the loop fall through.

Actually, we would never hint xfs_btree_increment() at all no matter the default or with my current change, because the left variable value is 1 as per the user space imap implementation, thus, it should be decreased to 0 in this point.

The problem is, how we define the user call interface originally, why it does not support a 2nd argument which can be used to specified a desired icount to return a limited number of inode mapping tables? i.e,

imap_f() {

        if (argc != 2)
                nent = 1;
        else
                nent = atoi(argv[1]);

	....
}

The imap command does not support another options but initialize bulkreq.icount = nent = 1; In kernel, the bcount is evaluated to 1 and if (bufidx == bcount) should be true anyway as below code logic:

bcount = MIN(left, (int)(PAGE_SIZE / sizeof(*buffer)));

if (bufidx == bcount) {
	....
	formatter();
	....
}

But, if the left value could be specified from the user progs, maybe we cannot simply assuming "stat == 1" is always be true, in particular, in next path for implementing per AG inumber mechanism, xfs_btree_increment() would probably succeed but "stat == 0" if there is no right neighbors, and if the user could specified the 2nd imap option.

Hence, in this patch, I only intended to fix the btree error handling mechanism as a preparation step to implement per AG inumber.

Quoted 4 lines

Also, I think the agino addition here becomes unnecessary when the lookup issue above is addressed.

Quoted 15 lines

fs/xfs/xfs_itable.c xfs_inumbers_fmt( · line 660

Quoted 10 lines

fs/xfs/xfs_itable.c +9 -1

-	}
+
+next_ag:
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+		xfs_buf_relse(agbp);
+		agbp = NULL;
+		agino = 0;
+	} while (++agno < mp->m_sb.sb_agcount);
+

... and just thinking about the logic that way highlights the bug here, where we bump agno due to the continue above (where IIUC, we intend to only move forward within the ag). Perhaps the ++agno should be part of the broken off 'next_ag' logic as well.

Can you please point out a bit more about the bug? We bump agno due to current run out of the current AG but the user want to show more imaps.

Thanks,
-Jeff

Quoted 23 lines · Jeff Liu

Quoted 22 lines · Brian Foster

Quoted 21 lines · Jeff Liu

From: Jie Liu <[email protected]>

To fetch the file system number tables, we currently just ignore the errors and proceed to loop over the next AG or bump agino to the next chunk in case of btree operations failed, that is not properly because those errors might hint us potential file system problems.

This patch rework xfs_inumbers() to handle the btree operation errors as well as the loop conditions. Also, add pre-checkups for the given inode, we can save alloc/free the format buffer once against an invalid inode number.

Signed-off-by Jie Liu <[email protected]>

---
 fs/xfs/xfs_itable.c | 163 +++++++++++++++++++++++-----------------------------
 1 file changed, 72 insertions(+), 91 deletions(-)

fs/xfs/xfs_itable.c +0 -0

index 692671c..4d262f6 100644

...

Quoted 19 lines

Quoted 8 lines

Quoted 8 lines

fs/xfs/xfs_itable.c +0 -8

-		error = xfs_inobt_get_rec(cur, &r, &i);
-		if (error || i == 0) {
-			xfs_buf_relse(agbp);
-			agbp = NULL;
-			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
-			cur = NULL;
-			agno++;
-			agino = 0;

Quoted 8 lines

fs/xfs/xfs_itable.c

Quoted 4 lines

fs/xfs/xfs_itable.c +3 -1

-			continue;
+		error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_GE, &stat);
+		if (error)
+			break;

Isn't this lookup only needed after cursor initialization? i.e., we lookup once and increment through the records via xfs_btree_increment() below.

Yes, but please see my comments below.

Quoted 1 line

...

Quoted 45 lines

Quoted 12 lines

Quoted 12 lines

fs/xfs/xfs_itable.c +12 -0

+		if (!--left)
+			break;
+
+		error = xfs_btree_increment(cur, 0, &stat);
+		if (error)
+			break;
+		if (stat) {
+			/*
+			 * The agino value has already been bumped, just try
+			 * to skip up to it.
+			 */
+			agino += XFS_INODES_PER_CHUNK;

Quoted 8 lines

fs/xfs/xfs_itable.c

Quoted 2 lines

fs/xfs/xfs_itable.c +1 -0

+			continue;
 		}

Maybe it's just me, but this reads a little funny to me. In particular because we only get here if stat == 1. I wonder if this would look a bit cleaner if we pulled the next_ag labeled block below up into the goto, since that appears to be the only reference. Then just let the loop fall through.

Actually, we would never hint xfs_btree_increment() at all no matter the default or with my current change, because the left variable value is 1 as per the user space imap implementation, thus, it should be decreased to 0 in this point.

The problem is, how we define the user call interface originally, why it does not support a 2nd argument which can be used to specified a desired icount to return a limited number of inode mapping tables? i.e,

imap_f() {

        if (argc != 2)
                nent = 1;
        else
                nent = atoi(argv[1]);

	....
}

The imap command does not support another options but initialize bulkreq.icount = nent = 1; In kernel, the bcount is evaluated to 1 and if (bufidx == bcount) should be true anyway as below code logic:

bcount = MIN(left, (int)(PAGE_SIZE / sizeof(*buffer)));

Quoted 5 lines

if (bufidx == bcount) {
	....
	formatter();
	....
}

Hi Jeff,

I see, but this is just a characteristic of the imap command in xfs_io. I can use an argument just by changing argmax from 0 to 1. Perhaps this is just a bug, since 'help imap' provides syntax that allows a parameter:

xfs_io> help imap
imap [nentries] -- inode map for filesystem of current file

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But, if the left value could be specified from the user progs, maybe we cannot simply assuming "stat == 1" is always be true, in particular, in next path for implementing per AG inumber mechanism, xfs_btree_increment() would probably succeed but "stat == 0" if there is no right neighbors, and if the user could specified the 2nd imap option.

Hmm, that looked odd to me as well once you pointed that out. A quick printk check shows that xfs_btree_increment() does not fail in this scenario, but the subsequent xfs_inobt_get_rec() in the following iteration sets i == 0 and skips to the next ag appropriately. I agree that a tmp == 0 check in this scenario would be slightly more intuitive though.

But either way, we should probably maintain the general algorithm of walking the btree explicitly rather than incrementing agino and issuing the lookup each iteration of the loop.

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Hence, in this patch, I only intended to fix the btree error handling mechanism as a preparation step to implement per AG inumber.

Right... I see that the following patches clean this up further (though I haven't looked in detail yet).

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Also, I think the agino addition here becomes unnecessary when the lookup issue above is addressed.

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fs/xfs/xfs_itable.c

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fs/xfs/xfs_itable.c +9 -1

-	}
+
+next_ag:
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+		xfs_buf_relse(agbp);
+		agbp = NULL;
+		agino = 0;
+	} while (++agno < mp->m_sb.sb_agcount);
+

... and just thinking about the logic that way highlights the bug here, where we bump agno due to the continue above (where IIUC, we intend to only move forward within the ag). Perhaps the ++agno should be part of the broken off 'next_ag' logic as well.

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Can you please point out a bit more about the bug? We bump agno due to current run out of the current AG but the user want to show more imaps.

agno is bumped in the while condition at the end of the loop. This will also be executed in the following block if xfs_btree_increment() succeeds and finds a record to the right:

                error = xfs_btree_increment(cur, 0, &stat);
                if (error)
                        break;
                if (stat) {
                        ...
                        agino += XFS_INODES_PER_CHUNK;
------>                 continue;
                }

The continue statement will execute the loop condition to determine whether it should iterate the loop again or break. In this case, you're still moving along the original AG, but agno has been bumped erroneously. This error looks to be hidden by the non-looping scenario where nentries is 1, but make the xfsprogs fix I described above and you'll probably see what I'm describing. I only see a subset of the original imap output using a record count of 10 on an fs with a couple thousand inodes spread across a couple AGs.

FWIW, it does look like the following patch fixes this particular problem via the introduction of xfs_perag_inumbers(), but we shouldn't introduce transient errors into the patch stream if we can help it.

It looks like the comments about the repeated inobt lookups still apply though (and the implementation as of patch 4 is still skipping inodes with nentries > 1, perhaps due to advancing agino multiple times per iteration..?).