Since use_pack() can already safely munmap packs to respect core.packedGitLimit, attempt to gracefully handle ENOMEM errors the same way by unmapping a window and retrying. This benefits unprivileged users who lack permissions to raise the `sys.vm.max_map_count' sysctl and/or RLIMIT_DATA resource limit. I've also verified it is safe to release a pack here by unconditionally calling unuse_one_window() before xmmap_gently(): --- a/packfile.c +++ b/packfile.c @@ -649,6 +649,7 @@ unsigned char *use_pack(struct packed_git *p, && unuse_one_window(p)) ; /* nothing */ do { + unuse_one_window(p); win->base = xmmap_gently(NULL, win->len, PROT_READ, MAP_PRIVATE, p->pack_fd, win->offset); Signed-off-by: Eric Wong <e@xxxxxxxxx> --- packfile.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/packfile.c b/packfile.c index 755aa7aec5..a0da790fb4 100644 --- a/packfile.c +++ b/packfile.c @@ -648,9 +648,12 @@ unsigned char *use_pack(struct packed_git *p, while (packed_git_limit < pack_mapped && unuse_one_window(p)) ; /* nothing */ - win->base = xmmap_gently(NULL, win->len, - PROT_READ, MAP_PRIVATE, - p->pack_fd, win->offset); + do { + win->base = xmmap_gently(NULL, win->len, + PROT_READ, MAP_PRIVATE, + p->pack_fd, win->offset); + } while (win->base == MAP_FAILED && errno == ENOMEM + && unuse_one_window(p)); if (win->base == MAP_FAILED) die_errno("packfile %s cannot be mapped", p->pack_name);