| 1 | /*
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| 2 | * Copyright (c) James Peach 2006, 2007
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| 3 | * Copyright (c) David Losada Carballo 2007
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| 4 | *
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| 5 | * This program is free software; you can redistribute it and/or modify
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| 6 | * it under the terms of the GNU General Public License as published by
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| 7 | * the Free Software Foundation; either version 3 of the License, or
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| 8 | * (at your option) any later version.
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| 9 | *
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| 10 | * This program is distributed in the hope that it will be useful,
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| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | * GNU General Public License for more details.
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| 14 | *
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| 15 | * You should have received a copy of the GNU General Public License
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| 16 | * along with this program; if not, see <http://www.gnu.org/licenses/>.
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| 17 | */
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| 18 |
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| 19 | #include "includes.h"
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| 20 |
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| 21 | /* Commit data module.
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| 22 | *
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| 23 | * The purpose of this module is to flush data to disk at regular intervals,
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| 24 | * just like the NFS commit operation. There's two rationales for this. First,
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| 25 | * it minimises the data loss in case of a power outage without incurring
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| 26 | * the poor performance of synchronous I/O. Second, a steady flush rate
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| 27 | * can produce better throughput than suddenly dumping massive amounts of
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| 28 | * writes onto a disk.
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| 29 | *
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| 30 | * Tunables:
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| 31 | *
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| 32 | * commit: dthresh Amount of dirty data that can accumulate
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| 33 | * before we commit (sync) it.
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| 34 | *
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| 35 | * commit: debug Debug level at which to emit messages.
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| 36 | *
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| 37 | * commit: eof mode String. Tunes how the module tries to guess when
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| 38 | * the client has written the last bytes of the file.
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| 39 | * Possible values (default = hinted):
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| 40 | *
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| 41 | * (*) = hinted Some clients (i.e. Windows Explorer) declare the
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| 42 | * size of the file before transferring it. With this
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| 43 | * option, we remember that hint, and commit after
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| 44 | * writing in that file position. If the client
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| 45 | * doesn't declare the size of file, commiting on EOF
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| 46 | * is not triggered.
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| 47 | *
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| 48 | * = growth Commits after a write operation has made the file
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| 49 | * size grow. If the client declares a file size, it
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| 50 | * refrains to commit until the file has reached it.
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| 51 | * Useful for defeating writeback on NFS shares.
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| 52 | *
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| 53 | */
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| 54 |
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| 55 | #define MODULE "commit"
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| 56 |
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| 57 | static int module_debug;
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| 58 |
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| 59 | enum eof_mode
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| 60 | {
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| 61 | EOF_NONE = 0x0000,
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| 62 | EOF_HINTED = 0x0001,
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| 63 | EOF_GROWTH = 0x0002
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| 64 | };
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| 65 |
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| 66 | struct commit_info
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| 67 | {
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| 68 | /* For chunk-based commits */
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| 69 | SMB_OFF_T dbytes; /* Dirty (uncommitted) bytes */
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| 70 | SMB_OFF_T dthresh; /* Dirty data threshold */
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| 71 | /* For commits on EOF */
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| 72 | enum eof_mode on_eof;
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| 73 | SMB_OFF_T eof; /* Expected file size */
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| 74 | };
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| 75 |
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| 76 | static int commit_do(
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| 77 | struct commit_info * c,
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| 78 | int fd)
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| 79 | {
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| 80 | int result;
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| 81 |
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| 82 | DEBUG(module_debug,
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| 83 | ("%s: flushing %lu dirty bytes\n",
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| 84 | MODULE, (unsigned long)c->dbytes));
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| 85 |
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| 86 | #if HAVE_FDATASYNC
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| 87 | result = fdatasync(fd);
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| 88 | #elif HAVE_FSYNC
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| 89 | result = fsync(fd);
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| 90 | #else
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| 91 | result = 0
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