[Cluster-devel] [GFS2 PATCH 3/4] gfs2: add new function gfs2_inpl_rsrv_ret_max_avl

[Abhi Das <adas@redhat.com>]

This is a variant of the existing gfs2_inplace_reserve() function.

If the requested number of blocks are not available to be reserved
from any of the rgrps, gfs2_inplace_reserve() return -ENOSPC.
gfs2_inpl_rsrv_ret_max_val() will also return the maximum blocks
available in an extra parameter 'max_avail'.

If acceptable to the caller logic, either of these inplace resreve
functions may be called again requesting 'max_avail' blocks to
avoid the -ENOSPC error.

Signed-off-by: Abhi Das <adas@redhat.com>
---
 fs/gfs2/rgrp.c | 13 +++++++++++--
 fs/gfs2/rgrp.h | 10 +++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 9150207..0fa9ae3 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1942,14 +1942,17 @@ static inline int fast_to_acquire(struct gfs2_rgrpd *rgd)
 }
 
 /**
- * gfs2_inplace_reserve - Reserve space in the filesystem
+ * gfs2_inpl_rsrv_ret_max_avl - Reserve space in the filesystem
  * @ip: the inode to reserve space for
  * @ap: the allocation parameters
+ * @max_avail: If non-NULL, return the max available extent if -ENOSPC
  *
  * Returns: errno
  */
 
-int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *ap)
+int gfs2_inpl_rsrv_ret_max_avl(struct gfs2_inode *ip,
+			       const struct gfs2_alloc_parms *ap,
+			       u32 *max_avail)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct gfs2_rgrpd *begin = NULL;
@@ -1958,6 +1961,7 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
 	u64 last_unlinked = NO_BLOCK;
 	int loops = 0;
 	u32 skip = 0;
+	u32 max_avlbl = 0;
 
 	if (sdp->sd_args.ar_rgrplvb)
 		flags |= GL_SKIP;
@@ -2030,6 +2034,8 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
 		if (rs->rs_rbm.rgd->rd_free_clone >= ap->target) {
 			ip->i_rgd = rs->rs_rbm.rgd;
 			return 0;
+		} else if (rs->rs_rbm.rgd->rd_free_clone > max_avlbl) {
+			max_avlbl = rs->rs_rbm.rgd->rd_free_clone;
 		}
 
 check_rgrp:
@@ -2068,6 +2074,9 @@ next_rgrp:
 			gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
 	}
 
+	if (max_avail)
+		*max_avail = max_avlbl;
+
 	return -ENOSPC;
 }
 
diff --git a/fs/gfs2/rgrp.h b/fs/gfs2/rgrp.h
index b104f4a..2adffca 100644
--- a/fs/gfs2/rgrp.h
+++ b/fs/gfs2/rgrp.h
@@ -41,7 +41,15 @@ extern void gfs2_rgrp_go_unlock(struct gfs2_holder *gh);
 extern struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip);
 
 #define GFS2_AF_ORLOV 1
-extern int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *ap);
+extern int gfs2_inpl_rsrv_ret_max_avl(struct gfs2_inode *ip,
+				      const struct gfs2_alloc_parms *ap,
+				      u32 *max_avail);
+static inline int gfs2_inplace_reserve(struct gfs2_inode *ip,
+				       const struct gfs2_alloc_parms *ap)
+{
+	return gfs2_inpl_rsrv_ret_max_avl(ip, ap, NULL);
+}
+
 extern void gfs2_inplace_release(struct gfs2_inode *ip);
 
 extern int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *n,
-- 
1.8.1.4