[SSSD] [PATCH] mmap_cache: Store corrupted mmap cache before reset

Jakub Hrozek jhrozek at redhat.com
Wed Aug 21 12:01:21 UTC 2013


On Wed, Aug 21, 2013 at 10:27:38AM +0200, Lukas Slebodnik wrote:
> On (21/08/13 09:50), Pavel Březina wrote:
> >On 08/19/2013 09:56 PM, Michal Židek wrote:
> >>+static void  sss_mc_save_corrupted(struct sss_mc_ctx *mc_ctx)
> >>+{
> >>+    int err;
> >>+    int fd = -1;
> >>+    ssize_t written;
> >>+    char *file = NULL;
> >>+    TALLOC_CTX *tmp_ctx;
> >>+
> >>+    if (mc_ctx == NULL) {
> >>+        DEBUG(SSSDBG_TRACE_FUNC,
> >>+              ("Cannot store uninitialized cache. Nothing to do.\n"));
> >>+        return;
> >>+    }
> >>+
> >>+    tmp_ctx = talloc_new(NULL);
> >>+    if (tmp_ctx == NULL) {
> >>+        DEBUG(SSSDBG_CRIT_FAILURE, ("Out of memory.\n"));
> >>+        return;
> >>+    }
> >>+
> >>+    file = talloc_asprintf(tmp_ctx, "%s_%s",
> >>+                           mc_ctx->file, "corrupted");
> >>+    if (file == NULL) {
> >>+        DEBUG(SSSDBG_CRIT_FAILURE, ("Out of memory.\n"));
> >>+        goto done;
> >>+    }
> >>+
> >>+    /* We will always store only the last problematic cache state */
> >>+    fd = creat(file, 0600);
> >>+    if (fd == -1) {
> >>+        err = errno;
> >>+        DEBUG(SSSDBG_CRIT_FAILURE,
> >>+              ("Failed to open file '%s' [%d]: %s\n",
> >>+               file, err, strerror(err)));
> >>+        goto done;
> >>+    }
> >>+
> >>+    written = write(fd, mc_ctx->mmap_base, mc_ctx->mmap_size);
> >
> >Shouldn't sss_atomic_write_s() be used?
> >
> >>+    if (written != mc_ctx->mmap_size) {
> >>+        if (written == -1) {
> >>+            err = errno;
> >>+            DEBUG(SSSDBG_CRIT_FAILURE,
> >>+                  ("write() failed [%d]: %s\n", err, strerror(err)));
> >>+        } else {
> >>+            DEBUG(SSSDBG_CRIT_FAILURE,
> >>+                  ("write() returned %zd (expected (%zd))\n",
> >>+                   written, mc_ctx->mmap_size));
> >>+        }
> >>+        goto done;
> >>+    }
> >
> >I think the file should be unlinked in case of error.
> >
> >>+
> >>+    sss_log(SSS_LOG_NOTICE,
> >>+            "Stored copy of corrupted mmap cache in file '%s\n'", file);
> >>+done:
> >>+    if (fd != -1) {
> >>+        close(fd);
> >>+    }
> >>+    talloc_free(tmp_ctx);
> >>+}
> 
> I think that function sss_mc_save_corrupted will never be called with patches
> from thread "[PATCHES] mmap_cache: Skip records which doesn't have same hash"
> 
> It is very likely that it is a dead code. I would prefer to ignore this
> nitpicks, because patches have already been pushed.
> 
> LS

No, sorry, I would prefer to always fix and improve code. At the very
least, existing code acts as a reference when developing new code.



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