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acme: check file content before declaring file "modified since last read"

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Bad remote file systems can change mtime unexpectedly,
and then there is the problem that git rebase and similar
operations like to change the files and then change them back,
modifying the mtimes but not the content.

Avoid spurious Put errors on both of those by checking file
content.

(False positive "modified since last read" make the real ones
difficult to notice.)
This commit is contained in:
Russ Cox 2017-10-10 13:49:37 -04:00
parent 680c57a15c
commit 67dbeee5fe
23 changed files with 79 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

37
src/cmd/acme/exec.c
View file

@ -9,6 +9,7 @@
#include <frame.h>
#include <fcall.h>
#include <plumb.h>
#include <libsec.h>
#include <9pclient.h>
#include "dat.h"
#include "fns.h"
@ -635,6 +636,30 @@ get(Text *et, Text *t, Text *argt, int flag1, int _0, Rune *arg, int narg)
xfidlog(w, "get");
}
static void
checksha1(char *name, File *f, Dir *d)
{
int fd, n;
DigestState *h;
uchar out[20];
uchar *buf;
fd = open(name, OREAD);
if(fd < 0)
return;
h = sha1(nil, 0, nil, nil);
buf = emalloc(8192);
while((n = read(fd, buf, 8192)) > 0)
sha1(buf, n, nil, h);
close(fd);
sha1(nil, 0, out, h);
if(memcmp(out, f->sha1, sizeof out) == 0) {
f->dev = d->dev;
f->qidpath = d->qid.path;
f->mtime = d->mtime;
}
}
void
putfile(File *f, int q0, int q1, Rune *namer, int nname)
{
@ -646,13 +671,15 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
Dir *d, *d1;
Window *w;
int isapp;
DigestState *h;
w = f->curtext->w;
name = runetobyte(namer, nname);
d = dirstat(name);
if(d!=nil && runeeq(namer, nname, f->name, f->nname)){
/* f->mtime+1 because when talking over NFS it's often off by a second */
if(f->dev!=d->dev || f->qidpath!=d->qid.path || labs((long)(f->mtime-d->mtime)) > 1){
if(f->dev!=d->dev || f->qidpath!=d->qid.path || f->mtime != d->mtime)
checksha1(name, f, d);
if(f->dev!=d->dev || f->qidpath!=d->qid.path || f->mtime != d->mtime) {
if(f->unread)
warning(nil, "%s not written; file already exists\n", name);
else
@ -679,6 +706,7 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
s = fbufalloc();
free(d);
d = dirfstat(fd);
h = sha1(nil, 0, nil, nil);
isapp = (d!=nil && d->length>0 && (d->qid.type&QTAPPEND));
if(isapp){
warning(nil, "%s not written; file is append only\n", name);
@ -691,6 +719,7 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
n = BUFSIZE/UTFmax;
bufread(&f->b, q, r, n);
m = snprint(s, BUFSIZE+1, "%.*S", n, r);
sha1((uchar*)s, m, nil, h);
if(Bwrite(b, s, m) != m){
warning(nil, "can't write file %s: %r\n", name);
goto Rescue2;
@ -730,6 +759,8 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
f->qidpath = d->qid.path;
f->dev = d->dev;
f->mtime = d->mtime;
sha1(nil, 0, f->sha1, h);
h = nil;
f->mod = FALSE;
w->dirty = FALSE;
f->unread = FALSE;
@ -741,6 +772,7 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
}
fbuffree(s);
fbuffree(r);
free(h);
free(d);
free(namer);
free(name);
@ -753,6 +785,7 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
Bterm(b);
free(b);
}
free(h);
fbuffree(s);
fbuffree(r);
close(fd);