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Merge branch 'ps/midx-negative-packfile-cache' 

When a stale .midx file refers to .pack files that no longer exist,
we ended up checking for these non-existent files repeatedly, which
has been optimized by memoizing the non-existence.

* ps/midx-negative-packfile-cache:
  midx: stop repeatedly looking up nonexistent packfiles
  packfile: explain ordering of how we look up auxiliary pack files
maint
Junio C Hamano 2025-05-30 11:59:18 -07:00
parent 1a140c870d 1f34bf3e08
commit 9a43523dc3
2 changed files with 21 additions and 2 deletions
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12
midx.c
View File

@ -13,6 +13,8 @@
#include "pack-bitmap.h" #include "pack-bitmap.h"
#include "pack-revindex.h" #include "pack-revindex.h"


#define MIDX_PACK_ERROR ((void *)(intptr_t)-1)

int midx_checksum_valid(struct multi_pack_index *m); int midx_checksum_valid(struct multi_pack_index *m);
void clear_midx_files_ext(const char *object_dir, const char *ext, void clear_midx_files_ext(const char *object_dir, const char *ext,
const char *keep_hash); const char *keep_hash);
@ -405,7 +407,7 @@ void close_midx(struct multi_pack_index *m)
munmap((unsigned char *)m->data, m->data_len); munmap((unsigned char *)m->data, m->data_len);


for (i = 0; i < m->num_packs; i++) { for (i = 0; i < m->num_packs; i++) {
if (m->packs[i]) if (m->packs[i] && m->packs[i] != MIDX_PACK_ERROR)
m->packs[i]->multi_pack_index = 0; m->packs[i]->multi_pack_index = 0;
} }
FREE_AND_NULL(m->packs); FREE_AND_NULL(m->packs);
@ -458,6 +460,8 @@ int prepare_midx_pack(struct repository *r, struct multi_pack_index *m,


pack_int_id = midx_for_pack(&m, pack_int_id); pack_int_id = midx_for_pack(&m, pack_int_id);


if (m->packs[pack_int_id] == MIDX_PACK_ERROR)
return 1;
if (m->packs[pack_int_id]) if (m->packs[pack_int_id])
return 0; return 0;


@ -482,8 +486,10 @@ int prepare_midx_pack(struct repository *r, struct multi_pack_index *m,
strbuf_release(&pack_name); strbuf_release(&pack_name);
strbuf_release(&key); strbuf_release(&key);


if (!p) if (!p) {
m->packs[pack_int_id] = MIDX_PACK_ERROR;
return 1; return 1;
}


p->multi_pack_index = 1; p->multi_pack_index = 1;
m->packs[pack_int_id] = p; m->packs[pack_int_id] = p;
@ -495,6 +501,8 @@ struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
uint32_t pack_int_id) uint32_t pack_int_id)
{ {
uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id); uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id);
if (m->packs[local_pack_int_id] == MIDX_PACK_ERROR)
return NULL;
return m->packs[local_pack_int_id]; return m->packs[local_pack_int_id];
} }



11
packfile.c
View File

@ -737,6 +737,17 @@ struct packed_git *add_packed_git(struct repository *r, const char *path,
p = alloc_packed_git(r, alloc); p = alloc_packed_git(r, alloc);
memcpy(p->pack_name, path, path_len); memcpy(p->pack_name, path, path_len);


/*
* Note that we have to check auxiliary data structures before we check
* for the ".pack" file to exist to avoid races with a packfile that is
* in the process of being deleted. The ".pack" file is unlinked before
* its auxiliary data structures, so we know that we either get a
* consistent snapshot of all data structures or that we'll fail to
* stat(3p) the packfile itself and thus return `NULL`.
*
* As such, we cannot bail out before the access(3p) calls in case the
* packfile doesn't exist without doing two stat(3p) calls for it.
*/
xsnprintf(p->pack_name + path_len, alloc - path_len, ".keep"); xsnprintf(p->pack_name + path_len, alloc - path_len, ".keep");
if (!access(p->pack_name, F_OK)) if (!access(p->pack_name, F_OK))
p->pack_keep = 1; p->pack_keep = 1;