From owner-freebsd-current@FreeBSD.ORG Thu Apr 23 03:20:48 2015 Return-Path: Delivered-To: current@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 9683224E for ; Thu, 23 Apr 2015 03:20:48 +0000 (UTC) Received: from vps1.elischer.org (vps1.elischer.org [204.109.63.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "vps1.elischer.org", Issuer "CA Cert Signing Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 75BAE1D9A for ; Thu, 23 Apr 2015 03:20:48 +0000 (UTC) Received: from Julian-MBP3.local (ppp121-45-229-105.lns20.per1.internode.on.net [121.45.229.105]) (authenticated bits=0) by vps1.elischer.org (8.14.9/8.14.9) with ESMTP id t3N3KhhZ018768 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO) for ; Wed, 22 Apr 2015 20:20:46 -0700 (PDT) (envelope-from julian@freebsd.org) Message-ID: <55386505.70708@freebsd.org> Date: Thu, 23 Apr 2015 11:20:37 +0800 From: Julian Elischer User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: "current@freebsd.org" Subject: readdir/telldir/seekdir problem (i think) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Apr 2015 03:20:48 -0000 I'm debugging a problem being seen with samba 3.6. basically telldir/seekdir/readdir don't seem to work as advertised.. here's a little test program #include #include #include #include #include #include #include #include #include #include #define CHUNKSIZE 5 #define TOTALFILES 40 static void SeekDir(DIR *dirp, long loc) { printf("Seeking back to location %ld\n", loc); seekdir(dirp, loc); } static long TellDir(DIR *dirp) { long loc; loc = telldir(dirp); printf("telldir assigned location %ld\n", loc); return (loc); } int main(int argc, char *argv[]) { DIR *dirp; int i; int j; long offset = 0, prev_offset = 0; char *files[100]; char filename[100]; int fd; struct dirent *dp = NULL; if (chdir("./test2") != 0) { err(EX_OSERR, "chdir"); } /*****************************************************/ /* Put a set of sample files in the target directory */ /*****************************************************/ for (i=1; i < TOTALFILES ; i++) { sprintf(filename, "file-%d", i); fd = open(filename, O_CREAT, 0666); if (fd == -1) { err(EX_OSERR, "open"); } close(fd); } dirp = opendir("."); offset = TellDir(dirp); for (i = 0; i < 20; i++) files[i] = malloc(20); /*******************************************************/ /* enumerate and delete small sets of files, one group */ /* at a time. */ /*******************************************************/ do { /*****************************************/ /* Read in up to CHUNKSIZE file names */ /* i will be the number of files we hold */ /*****************************************/ for (i = 0; i < CHUNKSIZE; i++) { if ((dp = readdir(dirp)) != NULL) { strcpy(files[i], dp->d_name); printf("readdir (%ld) returned file %s\n", offset, files[i]); prev_offset = offset; offset = TellDir(dirp); } else { printf("readdir returned null\n"); break; } } /****************************************************************/ /* Simuate the last entry not fitting into our (samba's) buffer */ /* If we read someting in on the last slot, push it back */ /* Pretend it didn't fit. This is approximately what SAMBA does.*/ /****************************************************************/ if (dp != NULL) { /* Step back */ SeekDir(dirp, prev_offset); offset = TellDir(dirp); i--; printf("file %s returned\n", files[i]); } /*****************************************/ /* i is the number of names we have left.*/ /* Delete them. */ /*****************************************/ for (j = 0; j < i; j++) { if (*files[j] == '.') { printf ("skipping %s\n", files[j]); } else { printf("Unlinking file %s\n", files[j]); if (unlink(files[j]) != 0) { err(EX_OSERR, "unlink"); } } } } while (dp != NULL); closedir(dirp); //chdir(".."); } The program is simulating what Samba does when fails. (doing a recursive delete of a directory) What it does is reads a chunk of names using readdir() until it's (small) buffer s full, then it uses seekdir() to seek back before the last entry it read, (which fails to fit), theortically leaving it for the next read. It then deletes the entries it found and repeats the cycle. Eventually it should have found all the files in the directory and deleted them. Except that it doesn't. What actually happens is that some files are not enumerated, even though the seekdir() should have made the readdir() find them. for added fun. the FIRST seekdir appears to work. but all subsequent ones don't. It behaves this way in -current , all the way back to at least 8.0. if there's a bug in my program please let me know, but samba has the same problem.. e.g. on freeNAS. to use the program make a directory called "./test2" and then run it in the current directory.. It fills it with files and then tried to (fails) delete them in small batches. here's some (annotated) output: ./testit telldir assigned location 0 readdir (0) returned file . telldir assigned location 1 readdir (1) returned file .. telldir assigned location 2 readdir (2) returned file file-1 telldir assigned location 3 readdir (3) returned file file-2 telldir assigned location 4 readdir (4) returned file file-3 telldir assigned location 5 >>>>> here we pretend the buffer was full and put the file >>>>> marker back so that it will get read next time Seeking back to location 4 telldir assigned location 4 file file-3 returned skipping . skipping .. Unlinking file file-1 Unlinking file file-2 readdir (4) returned file file-3 >>>>> hey it worked (this time) telldir assigned location 5 readdir (5) returned file file-4 telldir assigned location 6 readdir (6) returned file file-5 telldir assigned location 7 readdir (7) returned file file-6 telldir assigned location 8 readdir (8) returned file file-7 telldir assigned location 9 >>>>> OK do it again.. pretend file-7 didn't fit.. >>>>> set the pointer back so we re-read it next time. Seeking back to location 8 telldir assigned location 8 file file-7 returned Unlinking file file-3 Unlinking file file-4 Unlinking file file-5 Unlinking file file-6 >>>>> OK lets go get file-7 again readdir (8) returned file file-9 >>>>> WTF? what happened to file-7 ? telldir assigned location 9 readdir (9) returned file file-10 telldir assigned location 10