Re: No fsync on history file? I lost my history

[lilydjwg <lilydjwg@gmail.com>]

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I'm sending an updated patch.

On Sun, Sep 23, 2018 at 02:46:51PM +0000, Daniel Shahaf wrote:
> fsync() is in POSIX.  I assume we can just call it, but if somebody complains
> we'll need to use an HAVE_FSYNC guard.

I don't know how to add a HAVE_FSYNC macro to the build system, sorry.

> > +++ b/Src/hist.c
> > @@ -2933,6 +2933,9 @@ savehistfile(char *fn, int err, int writeflags)
> >  		lasthist.text = ztrdup(start);
> >  	    }
> >  	}
> > +	fflush(out); /* need to flush before fsync */
> 
> Isn't the fflush() on line 2927 sufficient?  (Even if it isn't, I would have
> expected a ret>=0 guard around this call.)

It should call write(2) to write out the buffered data. Then the kernel
can fsync the data to disk. A guard has been added.

> > +	if (fsync(fileno(out)) < 0 && ret >= 0)
> > +	    ret = -1;
> 
> fileno() can return -1.

It shouldn't matter, fsync will return EBADF for -1. Other parts of the
code don't check for this either, and I can't think a case when fileno
would fail after so many successful I/O operations on it (corrupted memory?)

> Shouldn't the ret>=0 check happen before the calls to fileno() and fsync()?

Yes, I've changed that.

-- 
Best regards,
lilydjwg

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From 3c6c07733f12176c737d1f610f0dceafd07437df Mon Sep 17 00:00:00 2001
From: lilydjwg <lilydjwg@gmail.com>
Date: Sun, 23 Sep 2018 22:12:56 +0800
Subject: [PATCH] Call fsync after writing out new histfile

to ensure the data is on disk before the rename in case of a system crash.
---
 Src/hist.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Src/hist.c b/Src/hist.c
index dbdc1e4e5..d3370252d 100644
--- a/Src/hist.c
+++ b/Src/hist.c
@@ -2933,6 +2933,10 @@ savehistfile(char *fn, int err, int writeflags)
 		lasthist.text = ztrdup(start);
 	    }
 	}
+	if (ret >= 0)
+	    ret = fflush(out); /* need to flush before fsync */
+	if (ret >= 0 && fsync(fileno(out)) < 0)
+	    ret = -1;
 	if (fclose(out) < 0 && ret >= 0)
 	    ret = -1;
 	if (ret >= 0) {
-- 
2.19.0