[XFS] Fix block reservation mechanism.
The block reservation mechanism has been broken since the per-cpu
superblock counters were introduced. Make the block reservation code work
with the per-cpu counters by syncing the counters, snapshotting the amount
of available space and then doing a modifcation of the counter state
according to the result. Continue in a loop until we either have no space
available or we reserve some space.
SGI-PV: 956323
SGI-Modid: xfs-linux-melb:xfs-kern:27895a
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index c064e72..bfde9e6 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -460,7 +460,7 @@
{
unsigned long s;
- xfs_icsb_sync_counters_lazy(mp);
+ xfs_icsb_sync_counters_flags(mp, XFS_ICSB_LAZY_COUNT);
s = XFS_SB_LOCK(mp);
cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
cnt->freertx = mp->m_sb.sb_frextents;
@@ -491,7 +491,7 @@
__uint64_t *inval,
xfs_fsop_resblks_t *outval)
{
- __int64_t lcounter, delta;
+ __int64_t lcounter, delta, fdblks_delta;
__uint64_t request;
unsigned long s;
@@ -504,17 +504,35 @@
}
request = *inval;
+
+ /*
+ * With per-cpu counters, this becomes an interesting
+ * problem. we needto work out if we are freeing or allocation
+ * blocks first, then we can do the modification as necessary.
+ *
+ * We do this under the XFS_SB_LOCK so that if we are near
+ * ENOSPC, we will hold out any changes while we work out
+ * what to do. This means that the amount of free space can
+ * change while we do this, so we need to retry if we end up
+ * trying to reserve more space than is available.
+ *
+ * We also use the xfs_mod_incore_sb() interface so that we
+ * don't have to care about whether per cpu counter are
+ * enabled, disabled or even compiled in....
+ */
+retry:
s = XFS_SB_LOCK(mp);
+ xfs_icsb_sync_counters_flags(mp, XFS_ICSB_SB_LOCKED);
/*
* If our previous reservation was larger than the current value,
* then move any unused blocks back to the free pool.
*/
-
+ fdblks_delta = 0;
if (mp->m_resblks > request) {
lcounter = mp->m_resblks_avail - request;
if (lcounter > 0) { /* release unused blocks */
- mp->m_sb.sb_fdblocks += lcounter;
+ fdblks_delta = lcounter;
mp->m_resblks_avail -= lcounter;
}
mp->m_resblks = request;
@@ -522,24 +540,50 @@
__int64_t free;
free = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
+ if (!free)
+ goto out; /* ENOSPC and fdblks_delta = 0 */
+
delta = request - mp->m_resblks;
lcounter = free - delta;
if (lcounter < 0) {
/* We can't satisfy the request, just get what we can */
mp->m_resblks += free;
mp->m_resblks_avail += free;
+ fdblks_delta = -free;
mp->m_sb.sb_fdblocks = XFS_ALLOC_SET_ASIDE(mp);
} else {
+ fdblks_delta = -delta;
mp->m_sb.sb_fdblocks =
lcounter + XFS_ALLOC_SET_ASIDE(mp);
mp->m_resblks = request;
mp->m_resblks_avail += delta;
}
}
-
+out:
outval->resblks = mp->m_resblks;
outval->resblks_avail = mp->m_resblks_avail;
XFS_SB_UNLOCK(mp, s);
+
+ if (fdblks_delta) {
+ /*
+ * If we are putting blocks back here, m_resblks_avail is
+ * already at it's max so this will put it in the free pool.
+ *
+ * If we need space, we'll either succeed in getting it
+ * from the free block count or we'll get an enospc. If
+ * we get a ENOSPC, it means things changed while we were
+ * calculating fdblks_delta and so we should try again to
+ * see if there is anything left to reserve.
+ *
+ * Don't set the reserved flag here - we don't want to reserve
+ * the extra reserve blocks from the reserve.....
+ */
+ int error;
+ error = xfs_mod_incore_sb(mp, XFS_SBS_FDBLOCKS, fdblks_delta, 0);
+ if (error == ENOSPC)
+ goto retry;
+ }
+
return 0;
}
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 0df07c1..30a5781 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1979,8 +1979,8 @@
xfs_icsb_unlock_all_counters(mp);
}
-STATIC void
-xfs_icsb_sync_counters_int(
+void
+xfs_icsb_sync_counters_flags(
xfs_mount_t *mp,
int flags)
{
@@ -2012,17 +2012,7 @@
xfs_icsb_sync_counters(
xfs_mount_t *mp)
{
- xfs_icsb_sync_counters_int(mp, 0);
-}
-
-/*
- * lazy addition used for things like df, background sb syncs, etc
- */
-void
-xfs_icsb_sync_counters_lazy(
- xfs_mount_t *mp)
-{
- xfs_icsb_sync_counters_int(mp, XFS_ICSB_LAZY_COUNT);
+ xfs_icsb_sync_counters_flags(mp, 0);
}
/*
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 9a8e715..b65dae6 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -307,7 +307,7 @@
#define XFS_ICSB_LAZY_COUNT (1 << 1) /* accuracy not needed */
extern int xfs_icsb_init_counters(struct xfs_mount *);
-extern void xfs_icsb_sync_counters_lazy(struct xfs_mount *);
+extern void xfs_icsb_sync_counters_flags(struct xfs_mount *, int);
#else
#define xfs_icsb_init_counters(mp) (0)
diff --git a/fs/xfs/xfs_vfsops.c b/fs/xfs/xfs_vfsops.c
index aec4e8d..f5ea74b 100644
--- a/fs/xfs/xfs_vfsops.c
+++ b/fs/xfs/xfs_vfsops.c
@@ -806,7 +806,7 @@
statp->f_type = XFS_SB_MAGIC;
- xfs_icsb_sync_counters_lazy(mp);
+ xfs_icsb_sync_counters_flags(mp, XFS_ICSB_LAZY_COUNT);
s = XFS_SB_LOCK(mp);
statp->f_bsize = sbp->sb_blocksize;
lsize = sbp->sb_logstart ? sbp->sb_logblocks : 0;