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