Date: Thu, 29 May 2008 23:43:05 +0300 From: Diomidis Spinellis <dds@aueb.gr> To: Andriy Gapon <avg@icyb.net.ua> Cc: Harti Brandt <harti@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: cp(1) and mmap Message-ID: <483F1559.2020600@aueb.gr> In-Reply-To: <483D5DF8.4020504@icyb.net.ua> References: <20080528110003.Q24259@beagle.kn.op.dlr.de> <483D5DF8.4020504@icyb.net.ua>
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Andriy Gapon wrote:
> on 28/05/2008 12:02 Harti Brandt said the following:
>> Hi all,
>>
>> it looks like there is no fallback in cp(1) when mmaping the source file
>> fails. I'm mounting SMB shares via smbnetfs (which in turn uses fuse)
>> and it seems not to support mmaping files. Shouldn't cp just fallback to
>> a normal read()/write() loop in this case?
>
> I would think that it should.
> This topic was brought up several times, but no resolution so far.
> I think that I've even seen patches.
>
I've not seen the patches, but the fix is trivial (see the attached
patch). If there are no objections, I can commit it.
I also think we should use mmap for larger files, mmapping and writing
them out in several chunks.
Diomidis - dds@
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Index: utils.c
===================================================================
RCS file: /home/ncvs/src/bin/cp/utils.c,v
retrieving revision 1.53
diff -u -r1.53 utils.c
--- utils.c 10 Mar 2008 19:58:41 -0000 1.53
+++ utils.c 29 May 2008 20:39:38 -0000
@@ -137,41 +137,39 @@
* Mmap and write if less than 8M (the limit is so we don't totally
* trash memory on big files. This is really a minor hack, but it
* wins some CPU back.
+ * Some filesystems, such as smbnetfs, don't support mmap,
+ * so this is a best-effort attempt.
*/
#ifdef VM_AND_BUFFER_CACHE_SYNCHRONIZED
if (S_ISREG(fs->st_mode) && fs->st_size > 0 &&
- fs->st_size <= 8 * 1048576) {
- if ((p = mmap(NULL, (size_t)fs->st_size, PROT_READ,
- MAP_SHARED, from_fd, (off_t)0)) == MAP_FAILED) {
+ fs->st_size <= 8 * 1048576 &&
+ (p = mmap(NULL, (size_t)fs->st_size, PROT_READ,
+ MAP_SHARED, from_fd, (off_t)0)) != MAP_FAILED) {
+ wtotal = 0;
+ for (bufp = p, wresid = fs->st_size; ;
+ bufp += wcount, wresid -= (size_t)wcount) {
+ wcount = write(to_fd, bufp, wresid);
+ if (wcount <= 0)
+ break;
+ wtotal += wcount;
+ if (info) {
+ info = 0;
+ (void)fprintf(stderr,
+ "%s -> %s %3d%%\n",
+ entp->fts_path, to.p_path,
+ cp_pct(wtotal, fs->st_size));
+ }
+ if (wcount >= (ssize_t)wresid)
+ break;
+ }
+ if (wcount != (ssize_t)wresid) {
+ warn("%s", to.p_path);
+ rval = 1;
+ }
+ /* Some systems don't unmap on close(2). */
+ if (munmap(p, fs->st_size) < 0) {
warn("%s", entp->fts_path);
rval = 1;
- } else {
- wtotal = 0;
- for (bufp = p, wresid = fs->st_size; ;
- bufp += wcount, wresid -= (size_t)wcount) {
- wcount = write(to_fd, bufp, wresid);
- if (wcount <= 0)
- break;
- wtotal += wcount;
- if (info) {
- info = 0;
- (void)fprintf(stderr,
- "%s -> %s %3d%%\n",
- entp->fts_path, to.p_path,
- cp_pct(wtotal, fs->st_size));
- }
- if (wcount >= (ssize_t)wresid)
- break;
- }
- if (wcount != (ssize_t)wresid) {
- warn("%s", to.p_path);
- rval = 1;
- }
- /* Some systems don't unmap on close(2). */
- if (munmap(p, fs->st_size) < 0) {
- warn("%s", entp->fts_path);
- rval = 1;
- }
}
} else
#endif
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