summaryrefslogtreecommitdiffstats
path: root/lib
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2018-04-30 16:53:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-30 16:53:40 -0700
commitfff75eb2a08c2ac96404a2d79685668f3cf5a7a3 (patch)
tree5a52f98e5f2247e1c348f31211c4e8b7230a5fa0 /lib
parent8188fc8bef8c677d28a9dbbd2db6deaee1644180 (diff)
parentb4678df184b314a2bd47d2329feca2c2534aa12b (diff)
downloadlinux-fff75eb2a08c2ac96404a2d79685668f3cf5a7a3.tar.gz
linux-fff75eb2a08c2ac96404a2d79685668f3cf5a7a3.tar.bz2
linux-fff75eb2a08c2ac96404a2d79685668f3cf5a7a3.zip
Merge tag 'errseq-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux
Pull errseq infrastructure fix from Jeff Layton: "The PostgreSQL developers recently had a spirited discussion about the writeback error handling in Linux, and reached out to us about a behavoir change to the code that bit them when the errseq_t changes were merged. When we changed to using errseq_t for tracking writeback errors, we lost the ability for an application to see a writeback error that occurred before the open on which the fsync was issued. This was problematic for PostgreSQL which offloads fsync calls to a completely separate process from the DB writers. This patch restores that ability. If the errseq_t value in the inode does not have the SEEN flag set, then we just return 0 for the sample. That ensures that any recorded error is always delivered at least once. Note that we might still lose the error if the inode gets evicted from the cache before anything can reopen it, but that was the case before errseq_t was merged. At LSF/MM we had some discussion about keeping inodes with unreported writeback errors around in the cache for longer (possibly indefinitely), but that's really a separate problem" * tag 'errseq-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux: errseq: Always report a writeback error once
Diffstat (limited to 'lib')
-rw-r--r--lib/errseq.c23
1 files changed, 9 insertions, 14 deletions
diff --git a/lib/errseq.c b/lib/errseq.c
index df782418b333..81f9e33aa7e7 100644
--- a/lib/errseq.c
+++ b/lib/errseq.c
@@ -111,27 +111,22 @@ EXPORT_SYMBOL(errseq_set);
* errseq_sample() - Grab current errseq_t value.
* @eseq: Pointer to errseq_t to be sampled.
*
- * This function allows callers to sample an errseq_t value, marking it as
- * "seen" if required.
+ * This function allows callers to initialise their errseq_t variable.
+ * If the error has been "seen", new callers will not see an old error.
+ * If there is an unseen error in @eseq, the caller of this function will
+ * see it the next time it checks for an error.
*
+ * Context: Any context.
* Return: The current errseq value.
*/
errseq_t errseq_sample(errseq_t *eseq)
{
errseq_t old = READ_ONCE(*eseq);
- errseq_t new = old;
- /*
- * For the common case of no errors ever having been set, we can skip
- * marking the SEEN bit. Once an error has been set, the value will
- * never go back to zero.
- */
- if (old != 0) {
- new |= ERRSEQ_SEEN;
- if (old != new)
- cmpxchg(eseq, old, new);
- }
- return new;
+ /* If nobody has seen this error yet, then we can be the first. */
+ if (!(old & ERRSEQ_SEEN))
+ old = 0;
+ return old;
}
EXPORT_SYMBOL(errseq_sample);