mem: fix freeing segments in --huge-unlink mode

When using huge_unlink we unlink the segment right
after allocation. Although we unlink the file we keep
the fd in fd_list so file still exist just the path deleted.
When freeing the hugepage we need to close the fd and assign
it with (-1) in fd_list for the page to be released.

The current flow fails rte_malloc in the following flow when working
with --huge-unlink option:
1. alloc_seg() for segment A -
    We allocate a segment, unlink the path to the segment
    and keep the file descriptor in fd_list.
2. free_seg() for segment A -
    We clear the segment metadata and return - without closing fd
    or assigning (-1) in fd list.
3. alloc_seg() for segment A again -
    We find segment A as available, try to allocate it,
    find the old fd in fd_list try to unlink it
    as part of alloc_seg() but failed because path doesn't exist.

The impact of such error is falsely failing rte_malloc()
although we have hugepages available.

Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
Cc: stable@dpdk.org
Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

diff --git a/lib/librte_eal/linux/eal_memalloc.c b/lib/librte_eal/linux/eal_memalloc.c
index 00e2662c15aed3d18fbd816a7b111b8e678260a4..0ec85422834777dbb4c9e4dba588eddc7701f503 100644 (file)
--- a/lib/librte_eal/linux/eal_memalloc.c
+++ b/lib/librte_eal/linux/eal_memalloc.c
@@ -709,7 +709,6 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
        uint64_t map_offset;
        char path[PATH_MAX];
        int fd, ret = 0;
-       bool exit_early;
        const struct internal_config *internal_conf =
                eal_get_internal_configuration();
 
@@ -725,17 +724,8 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 
        eal_mem_set_dump(ms->addr, ms->len, false);
 
-       exit_early = false;
-
        /* if we're using anonymous hugepages, nothing to be done */
-       if (internal_conf->in_memory && !memfd_create_supported)
-               exit_early = true;
-
-       /* if we've already unlinked the page, nothing needs to be done */
-       if (!internal_conf->in_memory && internal_conf->hugepage_unlink)
-               exit_early = true;
-
-       if (exit_early) {
+       if (internal_conf->in_memory && !memfd_create_supported) {
                memset(ms, 0, sizeof(*ms));
                return 0;
        }
@@ -761,7 +751,7 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
                /* if we're able to take out a write lock, we're the last one
                 * holding onto this page.
                 */
-               if (!internal_conf->in_memory) {
+               if (!internal_conf->in_memory && !internal_conf->hugepage_unlink) {
                        ret = lock(fd, LOCK_EX);
                        if (ret >= 0) {
                                /* no one else is using this page */