xfs: add online discard support

Now that we have reliably tracking of deleted extents in a
transaction we can easily implement "online" discard support
which calls blkdev_issue_discard once a transaction commits.

The actual discard is a two stage operation as we first have
to mark the busy extent as not available for reuse before we
can start the actual discard.  Note that we don't bother
supporting discard for the non-delaylog mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

9 files changed, 90 insertions, 8 deletions

diff --git a/fs/xfs/linux-2.6/xfs_discard.c b/fs/xfs/linux-2.6/xfs_discard.c
index d61611c88012..244e797dae32 100644
--- a/fs/xfs/linux-2.6/xfs_discard.c
+++ b/fs/xfs/linux-2.6/xfs_discard.c
@@ -191,3 +191,32 @@ xfs_ioc_trim(
                 return -XFS_ERROR(EFAULT);
         return 0;
 }
+
+int
+xfs_discard_extents(
+        struct xfs_mount        *mp,
+        struct list_head        *list)
+{
+        struct xfs_busy_extent  *busyp;
+        int                     error = 0;
+
+        list_for_each_entry(busyp, list, list) {
+                trace_xfs_discard_extent(mp, busyp->agno, busyp->bno,
+                                         busyp->length);
+
+                error = -blkdev_issue_discard(mp->m_ddev_targp->bt_bdev,
+                                XFS_AGB_TO_DADDR(mp, busyp->agno, busyp->bno),
+                                XFS_FSB_TO_BB(mp, busyp->length),
+                                GFP_NOFS, 0);
+                if (error && error != EOPNOTSUPP) {
+                        xfs_info(mp,
+         "discard failed for extent [0x%llu,%u], error %d",
+                                 (unsigned long long)busyp->bno,
+                                 busyp->length,
+                                 error);
+                        return error;
+                }
+        }
+
+        return 0;
+}
diff --git a/fs/xfs/linux-2.6/xfs_discard.h b/fs/xfs/linux-2.6/xfs_discard.h
index e82b6dd3e127..344879aea646 100644
--- a/fs/xfs/linux-2.6/xfs_discard.h
+++ b/fs/xfs/linux-2.6/xfs_discard.h
@@ -2,7 +2,9 @@
 #define XFS_DISCARD_H 1
 
 struct fstrim_range;
+struct list_head;
 
 extern int      xfs_ioc_trim(struct xfs_mount *, struct fstrim_range __user *);
+extern int      xfs_discard_extents(struct xfs_mount *, struct list_head *);
 
 #endif /* XFS_DISCARD_H */
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index b0aa59e51fd0..98b9c91fcdf1 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -110,8 +110,10 @@ mempool_t *xfs_ioend_pool;
 #define MNTOPT_GQUOTANOENF "gqnoenforce"/* group quota limit enforcement */
 #define MNTOPT_PQUOTANOENF "pqnoenforce"/* project quota limit enforcement */
 #define MNTOPT_QUOTANOENF  "qnoenforce" /* same as uqnoenforce */
-#define MNTOPT_DELAYLOG   "delaylog"    /* Delayed loging enabled */
-#define MNTOPT_NODELAYLOG "nodelaylog"  /* Delayed loging disabled */
+#define MNTOPT_DELAYLOG    "delaylog"   /* Delayed logging enabled */
+#define MNTOPT_NODELAYLOG  "nodelaylog" /* Delayed logging disabled */
+#define MNTOPT_DISCARD     "discard"    /* Discard unused blocks */
+#define MNTOPT_NODISCARD   "nodiscard"  /* Do not discard unused blocks */
 
 /*
  * Table driven mount option parser.
@@ -355,6 +357,10 @@ xfs_parseargs(
                         mp->m_flags |= XFS_MOUNT_DELAYLOG;
                 } else if (!strcmp(this_char, MNTOPT_NODELAYLOG)) {
                         mp->m_flags &= ~XFS_MOUNT_DELAYLOG;
+                } else if (!strcmp(this_char, MNTOPT_DISCARD)) {
+                        mp->m_flags |= XFS_MOUNT_DISCARD;
+                } else if (!strcmp(this_char, MNTOPT_NODISCARD)) {
+                        mp->m_flags &= ~XFS_MOUNT_DISCARD;
                 } else if (!strcmp(this_char, "ihashsize")) {
                         xfs_warn(mp,
         "ihashsize no longer used, option is deprecated.");
@@ -388,6 +394,13 @@ xfs_parseargs(
                 return EINVAL;
         }
 
+        if ((mp->m_flags & XFS_MOUNT_DISCARD) &&
+            !(mp->m_flags & XFS_MOUNT_DELAYLOG)) {
+                xfs_warn(mp,
+        "the discard option is incompatible with the nodelaylog option");
+                return EINVAL;
+        }
+
 #ifndef CONFIG_XFS_QUOTA
         if (XFS_IS_QUOTA_RUNNING(mp)) {
                 xfs_warn(mp, "quota support not available in this kernel.");
@@ -488,6 +501,7 @@ xfs_showargs(
                 { XFS_MOUNT_FILESTREAMS,        "," MNTOPT_FILESTREAM },
                 { XFS_MOUNT_GRPID,              "," MNTOPT_GRPID },
                 { XFS_MOUNT_DELAYLOG,           "," MNTOPT_DELAYLOG },
+                { XFS_MOUNT_DISCARD,            "," MNTOPT_DISCARD },
                 { 0, NULL }
         };
         static struct proc_xfs_info xfs_info_unset[] = {
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index da0a561ffba2..8d52ba4c87e5 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -187,6 +187,8 @@ struct xfs_busy_extent {
         xfs_agnumber_t  agno;
         xfs_agblock_t   bno;
         xfs_extlen_t    length;
+        unsigned int    flags;
+#define XFS_ALLOC_BUSY_DISCARDED        0x01    /* undergoing a discard op. */
 };
 
 /*
diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index acdced86413c..721db22c6ec9 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -2609,6 +2609,18 @@ xfs_alloc_busy_update_extent(
         xfs_agblock_t           bend = bbno + busyp->length;
 
         /*
+         * This extent is currently being discarded.  Give the thread
+         * performing the discard a chance to mark the extent unbusy
+         * and retry.
+         */
+        if (busyp->flags & XFS_ALLOC_BUSY_DISCARDED) {
+                spin_unlock(&pag->pagb_lock);
+                delay(1);
+                spin_lock(&pag->pagb_lock);
+                return false;
+        }
+
+        /*
          * If there is a busy extent overlapping a user allocation, we have
          * no choice but to force the log and retry the search.
          *
@@ -2813,7 +2825,8 @@ restart:
                  * If this is a metadata allocation, try to reuse the busy
                  * extent instead of trimming the allocation.
                  */
-                if (!args->userdata) {
+                if (!args->userdata &&
+                    !(busyp->flags & XFS_ALLOC_BUSY_DISCARDED)) {
                         if (!xfs_alloc_busy_update_extent(args->mp, args->pag,
                                                           busyp, fbno, flen,
                                                           false))
@@ -2979,10 +2992,16 @@ xfs_alloc_busy_clear_one(
         kmem_free(busyp);
 }
 
+/*
+ * Remove all extents on the passed in list from the busy extents tree.
+ * If do_discard is set skip extents that need to be discarded, and mark
+ * these as undergoing a discard operation instead.
+ */
 void
 xfs_alloc_busy_clear(
         struct xfs_mount        *mp,
-        struct list_head        *list)
+        struct list_head        *list,
+        bool                    do_discard)
 {
         struct xfs_busy_extent  *busyp, *n;
         struct xfs_perag        *pag = NULL;
@@ -2999,7 +3018,10 @@ xfs_alloc_busy_clear(
                         agno = busyp->agno;
                 }
 
-                xfs_alloc_busy_clear_one(mp, pag, busyp);
+                if (do_discard && busyp->length)
+                        busyp->flags = XFS_ALLOC_BUSY_DISCARDED;
+                else
+                        xfs_alloc_busy_clear_one(mp, pag, busyp);
         }
 
         if (pag) {
diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h
index 240ad288f2f9..06aa8217452b 100644
--- a/fs/xfs/xfs_alloc.h
+++ b/fs/xfs/xfs_alloc.h
@@ -140,7 +140,8 @@ xfs_alloc_busy_insert(struct xfs_trans *tp, xfs_agnumber_t agno,
         xfs_agblock_t bno, xfs_extlen_t len);
 
 void
-xfs_alloc_busy_clear(struct xfs_mount *mp, struct list_head *list);
+xfs_alloc_busy_clear(struct xfs_mount *mp, struct list_head *list,
+        bool do_discard);
 
 int
 xfs_alloc_busy_search(struct xfs_mount *mp, xfs_agnumber_t agno,
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 7d56e88a3f0e..c7755d5a5fbe 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -29,6 +29,7 @@
 #include "xfs_mount.h"
 #include "xfs_error.h"
 #include "xfs_alloc.h"
+#include "xfs_discard.h"
 
 /*
  * Perform initial CIL structure initialisation. If the CIL is not
@@ -361,18 +362,28 @@ xlog_cil_committed(
         int     abort)
 {
         struct xfs_cil_ctx      *ctx = args;
+        struct xfs_mount        *mp = ctx->cil->xc_log->l_mp;
 
         xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
                                         ctx->start_lsn, abort);
 
         xfs_alloc_busy_sort(&ctx->busy_extents);
-        xfs_alloc_busy_clear(ctx->cil->xc_log->l_mp, &ctx->busy_extents);
+        xfs_alloc_busy_clear(mp, &ctx->busy_extents,
+                             (mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
 
         spin_lock(&ctx->cil->xc_cil_lock);
         list_del(&ctx->committing);
         spin_unlock(&ctx->cil->xc_cil_lock);
 
         xlog_cil_free_logvec(ctx->lv_chain);
+
+        if (!list_empty(&ctx->busy_extents)) {
+                ASSERT(mp->m_flags & XFS_MOUNT_DISCARD);
+
+                xfs_discard_extents(mp, &ctx->busy_extents);
+                xfs_alloc_busy_clear(mp, &ctx->busy_extents, false);
+        }
+
         kmem_free(ctx);
 }
 
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 19af0ab0d0c6..3d68bb267c5f 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -224,6 +224,7 @@ typedef struct xfs_mount {
 #define XFS_MOUNT_FS_SHUTDOWN   (1ULL << 4)     /* atomic stop of all filesystem
                                                    operations, typically for
                                                    disk errors in metadata */
+#define XFS_MOUNT_DISCARD       (1ULL << 5)     /* discard unused blocks */
 #define XFS_MOUNT_RETERR        (1ULL << 6)     /* return alignment errors to
                                                    user */
 #define XFS_MOUNT_NOALIGN       (1ULL << 7)     /* turn off stripe alignment
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index d1f24858ccc4..7c7bc2b786bd 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -609,7 +609,7 @@ xfs_trans_free(
         struct xfs_trans        *tp)
 {
         xfs_alloc_busy_sort(&tp->t_busy);
-        xfs_alloc_busy_clear(tp->t_mountp, &tp->t_busy);
+        xfs_alloc_busy_clear(tp->t_mountp, &tp->t_busy, false);
 
         atomic_dec(&tp->t_mountp->m_active_trans);
         xfs_trans_free_dqinfo(tp);