LU-9679 osc: simplify osc_extent_find()

osc_extent_find() contains some code with the same functionality as
osc_extent_merge().  So replace that code with a call to
osc_extent_merge().

This requires that we set cur->oe_grants earlier, as
osc_extent_merge() needs that.

Also:

 - fix a pre-existing bug - osc_extent_merge() should never try to
   merge two extends with different ->oe_mppr as later alignment
   checks can get confused.
 - Remove a redundant list_del_init() which is already included in
   __osc_extent_remove().

Linux-Commit: 85ebb57ddc5b ("lustre: osc: simplify osc_extent_find()")

Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: I5fa56e04ed707ee91f99179030dae4bd45456061
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Reviewed-on: https://review.whamcloud.com/37607
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/osc/osc_cache.c b/lustre/osc/osc_cache.c
index 613a056..e0c9901 100644 (file)
--- a/lustre/osc/osc_cache.c
+++ b/lustre/osc/osc_cache.c
@@ -537,6 +537,14 @@ static int osc_extent_merge(const struct lu_env *env, struct osc_extent *cur,
        if (cur->oe_max_end != victim->oe_max_end)
                return -ERANGE;
 
+       /*
+        * In the rare case max_pages_per_rpc (mppr) is changed, don't
+        * merge extents until after old ones have been sent, or the
+        * "extents are aligned to RPCs" checks are unhappy.
+        */
+       if (cur->oe_mppr != victim->oe_mppr)
+               return -ERANGE;
+
        LASSERT(cur->oe_dlmlock == victim->oe_dlmlock);
        ppc_bits = osc_cli(obj)->cl_chunkbits - PAGE_SHIFT;
        chunk_start = cur->oe_start >> ppc_bits;
@@ -562,7 +570,6 @@ static int osc_extent_merge(const struct lu_env *env, struct osc_extent *cur,
        cur->oe_urgent   |= victim->oe_urgent;
        cur->oe_memalloc |= victim->oe_memalloc;
        list_splice_init(&victim->oe_pages, &cur->oe_pages);
-       list_del_init(&victim->oe_link);
        victim->oe_nr_pages = 0;
 
        osc_extent_get(victim);
@@ -690,7 +697,7 @@ static struct osc_extent *osc_extent_find(const struct lu_env *env,
                cur->oe_start = descr->cld_start;
        if (cur->oe_end > max_end)
                cur->oe_end = max_end;
-       cur->oe_grants  = 0;
+       cur->oe_grants  = chunksize + cli->cl_grant_extent_tax;
        cur->oe_mppr    = max_pages;
        if (olck->ols_dlmlock != NULL) {
                LASSERT(olck->ols_hold);
@@ -758,54 +765,21 @@ restart:
                         * flushed, try next one. */
                        continue;
 
-               /* check if they belong to the same rpc slot before trying to
-                * merge. the extents are not overlapped and contiguous at
-                * chunk level to get here. */
-               if (ext->oe_max_end != max_end)
-                       /* if they don't belong to the same RPC slot or
-                        * max_pages_per_rpc has ever changed, do not merge. */
-                       continue;
-
-               /* check whether maximum extent size will be hit */
-               if ((ext_chk_end - ext_chk_start + 1 + 1) << ppc_bits >
-                   cli->cl_max_extent_pages)
-                       continue;
-
-               /* it's required that an extent must be contiguous at chunk
-                * level so that we know the whole extent is covered by grant
-                * (the pages in the extent are NOT required to be contiguous).
-                * Otherwise, it will be too much difficult to know which
-                * chunks have grants allocated. */
-
-               /* try to do front merge - extend ext's start */
-               if (chunk + 1 == ext_chk_start) {
-                       /* ext must be chunk size aligned */
-                       EASSERT((ext->oe_start & ~chunk_mask) == 0, ext);
-
-                       /* pull ext's start back to cover cur */
-                       ext->oe_start   = cur->oe_start;
-                       ext->oe_grants += chunksize;
+               if (osc_extent_merge(env, ext, cur) == 0) {
                        LASSERT(*grants >= chunksize);
                        *grants -= chunksize;
-
                        found = osc_extent_hold(ext);
-               } else if (chunk == ext_chk_end + 1) {
-                       /* rear merge */
-                       ext->oe_end     = cur->oe_end;
-                       ext->oe_grants += chunksize;
-                       LASSERT(*grants >= chunksize);
-                       *grants -= chunksize;
 
-                       /* try to merge with the next one because we just fill
-                        * in a gap */
+                       /*
+                        * Try to merge with the next one too because we
+                        * might have just filled in a gap.
+                        */
                        if (osc_extent_merge(env, ext, next_extent(ext)) == 0)
                                /* we can save extent tax from next extent */
                                *grants += cli->cl_grant_extent_tax;
 
-                       found = osc_extent_hold(ext);
-               }
-               if (found != NULL)
                        break;
+               }
        }
 
        osc_extent_tree_dump(D_CACHE, obj);
@@ -819,7 +793,6 @@ restart:
        } else if (conflict == NULL) {
                /* create a new extent */
                EASSERT(osc_extent_is_overlapped(obj, cur) == 0, cur);
-               cur->oe_grants = chunksize + cli->cl_grant_extent_tax;
                LASSERT(*grants >= cur->oe_grants);
                *grants -= cur->oe_grants;