From 997778e332e9f6d3d1c42e9a222fcab8d4732c40 Mon Sep 17 00:00:00 2001 From: Michal Sekletar Date: Fri, 27 May 2016 14:29:17 +0200 Subject: [PATCH] readahead: do not increase nr_requests for root fs block device Having nr_requests can cause system lockups. Arguably, this should get fixed somehow in kernel. For now we just stop changing the value. Note that not bumping a value may cause that posix_fadvise call will block in case there is no room in a request queue. See: http://article.gmane.org/gmane.linux.kernel/1072356 RHEL-only Resolves: #1314559 --- src/readahead/readahead-common.c | 64 ---------------------------------------- src/readahead/readahead-common.h | 2 -- src/readahead/readahead-replay.c | 2 -- 3 files changed, 68 deletions(-) diff --git a/src/readahead/readahead-common.c b/src/readahead/readahead-common.c index 3ca48a7..6cf33f7 100644 --- a/src/readahead/readahead-common.c +++ b/src/readahead/readahead-common.c @@ -253,70 +253,6 @@ ReadaheadShared *shared_get(void) { return m; } -/* We use 20K instead of the more human digestable 16K here. Why? - Simply so that it is more unlikely that users end up picking this - value too so that we can recognize better whether the user changed - the value while we had it temporarily bumped. */ -#define BUMP_REQUEST_NR (20*1024u) - -int block_bump_request_nr(const char *p) { - struct stat st; - uint64_t u; - char *ap = NULL, *line = NULL; - int r; - dev_t d; - - assert(p); - - if (stat(p, &st) < 0) - return -errno; - - if (major(st.st_dev) == 0) - return 0; - - d = st.st_dev; - block_get_whole_disk(d, &d); - - if (asprintf(&ap, "/sys/dev/block/%u:%u/queue/nr_requests", major(d), minor(d)) < 0) { - r= -ENOMEM; - goto finish; - } - - r = read_one_line_file(ap, &line); - if (r < 0) { - if (r == -ENOENT) - r = 0; - goto finish; - } - - r = safe_atou64(line, &u); - if (r >= 0 && u >= BUMP_REQUEST_NR) { - r = 0; - goto finish; - } - - free(line); - line = NULL; - - if (asprintf(&line, "%u", BUMP_REQUEST_NR) < 0) { - r = -ENOMEM; - goto finish; - } - - r = write_string_file(ap, line); - if (r < 0) - goto finish; - - log_info("Bumped block_nr parameter of %u:%u to %u. This is a temporary hack and should be removed one day.", major(d), minor(d), BUMP_REQUEST_NR); - r = 1; - -finish: - free(ap); - free(line); - - return r; -} - int block_get_readahead(const char *p, uint64_t *bytes) { struct stat st; char *ap = NULL, *line = NULL; diff --git a/src/readahead/readahead-common.h b/src/readahead/readahead-common.h index b34f3aa..cc2ea81 100644 --- a/src/readahead/readahead-common.h +++ b/src/readahead/readahead-common.h @@ -51,8 +51,6 @@ typedef struct ReadaheadShared { ReadaheadShared *shared_get(void); -int block_bump_request_nr(const char *p); - int block_get_readahead(const char *p, uint64_t *bytes); int block_set_readahead(const char *p, uint64_t bytes); diff --git a/src/readahead/readahead-replay.c b/src/readahead/readahead-replay.c index f81e0fe..c2e2816 100644 --- a/src/readahead/readahead-replay.c +++ b/src/readahead/readahead-replay.c @@ -134,8 +134,6 @@ static int replay(const char *root) { assert(root); - block_bump_request_nr(root); - if (asprintf(&pack_fn, "%s/.readahead", root) < 0) return log_oom();