[SSSD] [PATCH] mmap_cache: Store corrupted mmap cache before reset
Jakub Hrozek
jhrozek at redhat.com
Thu Aug 22 17:48:04 UTC 2013
On Thu, Aug 22, 2013 at 10:45:40AM +0200, Pavel Březina wrote:
> On 08/22/2013 01:20 AM, Michal Židek wrote:
> >On 08/21/2013 04:47 PM, Michal Židek wrote:
> >>On 08/21/2013 02:01 PM, Jakub Hrozek wrote:
> >>>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?
> >>
> >>sss_atomic_write_s is probably better. I though that the function
> >>is only useful for non-blocking sockets, but after reading it's code I
> >>see it is good to use it here too.
> >>
> >>>>>>+ 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.
> >>
> >>Ok. I added unlink() call for the case if write returns -1. If the
> >>file was only partially written (for whatever reason) it can still
> >>hold some useful information, so I would prefer to keep it.
> >>
> >>>>>
> >>>>>>+
> >>>>>>+ 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.
> >>
> >>Since the original patch was already pushed, this one just adds the
> >>requested changes.
> >>
> >>Thanks
> >>Michal
> >>
> >
> >Since this was not yet pushed I did one more cosmetic change. I think
> >calling the close() before unlink() is more readable. If the fd != -1 we
> >already know that we want to close it, so the conditional check for
> >unlink() just makes noise before it. And this order is probably more
> >natural for most cases.
> >
> >Michal
>
> Ack.
Pushed to master.
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