From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 3 May 2012 22:34:12 +0000 (+0200)
Subject: readahead: store inode numbers in pack file
X-Git-Tag: v183~160
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=189455ab08a70f0c80a11847b65ce38563b9332a;ds=inline

readahead: store inode numbers in pack file

If the inode nr for each file is available in the pack file we can
easily detect replaced files (like they result from package upgrades)
which we can then skip to readahead.
---

diff --git a/TODO b/TODO
index f2c5dd6cc..db422c008 100644
--- a/TODO
+++ b/TODO
@@ -254,8 +254,6 @@ Features:
 
 * drop /.readahead on bigger upgrades with yum
 
-* add inode nr check to readahead to suppress preloading changed files
-
 * add support for /bin/mount -s
 
 * GC unreferenced jobs (such as .device jobs)
diff --git a/src/readahead/readahead-collect.c b/src/readahead/readahead-collect.c
index a88e7f2d7..359b97bf0 100644
--- a/src/readahead/readahead-collect.c
+++ b/src/readahead/readahead-collect.c
@@ -86,6 +86,7 @@ static int pack_file(FILE *pack, const char *fn, bool on_btrfs) {
         void *start = MAP_FAILED;
         uint8_t *vec;
         uint32_t b, c;
+        uint64_t inode;
         size_t l, pages;
         bool mapped;
         int r = 0, fd = -1, k;
@@ -93,7 +94,8 @@ static int pack_file(FILE *pack, const char *fn, bool on_btrfs) {
         assert(pack);
         assert(fn);
 
-        if ((fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW)) < 0) {
+        fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0) {
 
                 if (errno == ENOENT)
                         return 0;
@@ -106,7 +108,8 @@ static int pack_file(FILE *pack, const char *fn, bool on_btrfs) {
                 goto finish;
         }
 
-        if ((k = file_verify(fd, fn, arg_file_size_max, &st)) <= 0) {
+        k = file_verify(fd, fn, arg_file_size_max, &st);
+        if (k <= 0) {
                 r = k;
                 goto finish;
         }
@@ -115,14 +118,14 @@ static int pack_file(FILE *pack, const char *fn, bool on_btrfs) {
                 btrfs_defrag(fd);
 
         l = PAGE_ALIGN(st.st_size);
-        if ((start = mmap(NULL, l, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
+        start = mmap(NULL, l, PROT_READ, MAP_SHARED, fd, 0);
+        if (start == MAP_FAILED) {
                 log_warning("mmap(%s) failed: %m", fn);
                 r = -errno;
                 goto finish;
         }
 
         pages = l / page_size();
-
         vec = alloca(pages);
         memset(vec, 0, pages);
         if (mincore(start, l, vec) < 0) {
@@ -134,6 +137,10 @@ static int pack_file(FILE *pack, const char *fn, bool on_btrfs) {
         fputs(fn, pack);
         fputc('\n', pack);
 
+        /* Store the inode, so that we notice when the file is deleted */
+        inode = (uint64_t) st.st_ino;
+        fwrite(&inode, sizeof(inode), 1, pack);
+
         mapped = false;
         for (c = 0; c < pages; c++) {
                 bool new_mapped = !!(vec[c] & 1);
@@ -479,13 +486,14 @@ done:
                 goto finish;
         }
 
-        if (!(pack = fopen(pack_fn_new, "we"))) {
+        pack = fopen(pack_fn_new, "we");
+        if (!pack) {
                 log_error("Failed to open pack file: %m");
                 r = -errno;
                 goto finish;
         }
 
-        fputs(CANONICAL_HOST "\n", pack);
+        fputs(CANONICAL_HOST ";VERSION=2\n", pack);
         putc(on_ssd ? 'S' : 'R', pack);
 
         if (on_ssd || on_btrfs) {
diff --git a/src/readahead/readahead-replay.c b/src/readahead/readahead-replay.c
index a6529f8ba..886e16f29 100644
--- a/src/readahead/readahead-replay.c
+++ b/src/readahead/readahead-replay.c
@@ -53,6 +53,7 @@ static int unpack_file(FILE *pack) {
         int r = 0, fd = -1;
         bool any = false;
         struct stat st;
+        uint64_t inode;
 
         assert(pack);
 
@@ -62,7 +63,8 @@ static int unpack_file(FILE *pack) {
         char_array_0(fn);
         truncate_nl(fn);
 
-        if ((fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW)) < 0) {
+        fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0) {
 
                 if (errno != ENOENT && errno != EPERM && errno != EACCES)
                         log_warning("open(%s) failed: %m", fn);
@@ -72,6 +74,21 @@ static int unpack_file(FILE *pack) {
                 fd = -1;
         }
 
+        if (fread(&inode, sizeof(inode), 1, pack) != 1) {
+                log_error("Premature end of pack file.");
+                r = -EIO;
+                goto finish;
+        }
+
+        if (fd >= 0) {
+                /* If the inode changed the file got deleted, so just
+                 * ignore this entry */
+                if (st.st_ino != (uint64_t) inode) {
+                        close_nointr_nofail(fd);
+                        fd = -1;
+                }
+        }
+
         for (;;) {
                 uint32_t b, c;
 
@@ -166,8 +183,8 @@ static int replay(const char *root) {
 
         char_array_0(line);
 
-        if (!streq(line, CANONICAL_HOST "\n")) {
-                log_debug("Pack file host type mismatch.");
+        if (!streq(line, CANONICAL_HOST ";VERSION=2\n")) {
+                log_debug("Pack file host or version type mismatch.");
                 goto finish;
         }