├── .gitignore ├── LICENSE ├── Makefile ├── README.md ├── dir.c ├── file.c ├── hellofs-test.sh ├── hellofs.h ├── inode.c ├── khellofs.c ├── khellofs.h ├── mkfs-hellofs.c └── super.c /.gitignore: -------------------------------------------------------------------------------- 1 | # Object files 2 | *.o 3 | *.ko 4 | *.obj 5 | *.elf 6 | 7 | # Precompiled Headers 8 | *.gch 9 | *.pch 10 | 11 | # Libraries 12 | *.lib 13 | *.a 14 | *.la 15 | *.lo 16 | 17 | # Shared objects (inc. Windows DLLs) 18 | *.dll 19 | *.so 20 | *.so.* 21 | *.dylib 22 | 23 | # Executables 24 | *.exe 25 | *.out 26 | *.app 27 | *.i*86 28 | *.x86_64 29 | *.hex 30 | 31 | # Debug files 32 | *.dSYM/ -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | ========================== 3 | 4 | Version 3, 29 June 2007 5 | 6 | Copyright © 2007 Free Software Foundation, Inc. <> 7 | 8 | Everyone is permitted to copy and distribute verbatim copies of this license 9 | document, but changing it is not allowed. 10 | 11 | ## Preamble 12 | 13 | The GNU General Public License is a free, copyleft license for software and other 14 | kinds of works. 15 | 16 | The licenses for most software and other practical works are designed to take away 17 | your freedom to share and change the works. By contrast, the GNU General Public 18 | License is intended to guarantee your freedom to share and change all versions of a 19 | program--to make sure it remains free software for all its users. We, the Free 20 | Software Foundation, use the GNU General Public License for most of our software; it 21 | applies also to any other work released this way by its authors. You can apply it to 22 | your programs, too. 23 | 24 | When we speak of free software, we are referring to freedom, not price. Our General 25 | Public Licenses are designed to make sure that you have the freedom to distribute 26 | copies of free software (and charge for them if you wish), that you receive source 27 | code or can get it if you want it, that you can change the software or use pieces of 28 | it in new free programs, and that you know you can do these things. 29 | 30 | To protect your rights, we need to prevent others from denying you these rights or 31 | asking you to surrender the rights. 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If additional permissions apply only to part of the Program, that part may be 307 | used separately under those permissions, but the entire Program remains governed by 308 | this License without regard to the additional permissions. 309 | 310 | When you convey a copy of a covered work, you may at your option remove any 311 | additional permissions from that copy, or from any part of it. (Additional 312 | permissions may be written to require their own removal in certain cases when you 313 | modify the work.) 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If the Program as you received 339 | it, or any part of it, contains a notice stating that it is governed by this License 340 | along with a term that is a further restriction, you may remove that term. If a 341 | license document contains a further restriction but permits relicensing or conveying 342 | under this License, you may add to a covered work material governed by the terms of 343 | that license document, provided that the further restriction does not survive such 344 | relicensing or conveying. 345 | 346 | If you add terms to a covered work in accord with this section, you must place, in 347 | the relevant source files, a statement of the additional terms that apply to those 348 | files, or a notice indicating where to find the applicable terms. 349 | 350 | Additional terms, permissive or non-permissive, may be stated in the form of a 351 | separately written license, or stated as exceptions; the above requirements apply 352 | either way. 353 | 354 | ### 8. Termination. 355 | 356 | You may not propagate or modify a covered work except as expressly provided under 357 | this License. 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If your 375 | rights have been terminated and not permanently reinstated, you do not qualify to 376 | receive new licenses for the same material under section 10. 377 | 378 | ### 9. Acceptance Not Required for Having Copies. 379 | 380 | You are not required to accept this License in order to receive or run a copy of the 381 | Program. Ancillary propagation of a covered work occurring solely as a consequence of 382 | using peer-to-peer transmission to receive a copy likewise does not require 383 | acceptance. However, nothing other than this License grants you permission to 384 | propagate or modify any covered work. These actions infringe copyright if you do not 385 | accept this License. Therefore, by modifying or propagating a covered work, you 386 | indicate your acceptance of this License to do so. 387 | 388 | ### 10. Automatic Licensing of Downstream Recipients. 389 | 390 | Each time you convey a covered work, the recipient automatically receives a license 391 | from the original licensors, to run, modify and propagate that work, subject to this 392 | License. You are not responsible for enforcing compliance by third parties with this 393 | License. 394 | 395 | An “entity transaction” is a transaction transferring control of an 396 | organization, or substantially all assets of one, or subdividing an organization, or 397 | merging organizations. If propagation of a covered work results from an entity 398 | transaction, each party to that transaction who receives a copy of the work also 399 | receives whatever licenses to the work the party's predecessor in interest had or 400 | could give under the previous paragraph, plus a right to possession of the 401 | Corresponding Source of the work from the predecessor in interest, if the predecessor 402 | has it or can get it with reasonable efforts. 403 | 404 | You may not impose any further restrictions on the exercise of the rights granted or 405 | affirmed under this License. For example, you may not impose a license fee, royalty, 406 | or other charge for exercise of rights granted under this License, and you may not 407 | initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging 408 | that any patent claim is infringed by making, using, selling, offering for sale, or 409 | importing the Program or any portion of it. 410 | 411 | ### 11. Patents. 412 | 413 | A “contributor” is a copyright holder who authorizes use under this 414 | License of the Program or a work on which the Program is based. The work thus 415 | licensed is called the contributor's “contributor version”. 416 | 417 | A contributor's “essential patent claims” are all patent claims owned or 418 | controlled by the contributor, whether already acquired or hereafter acquired, that 419 | would be infringed by some manner, permitted by this License, of making, using, or 420 | selling its contributor version, but do not include claims that would be infringed 421 | only as a consequence of further modification of the contributor version. For 422 | purposes of this definition, “control” includes the right to grant patent 423 | sublicenses in a manner consistent with the requirements of this License. 424 | 425 | Each contributor grants you a non-exclusive, worldwide, royalty-free patent license 426 | under the contributor's essential patent claims, to make, use, sell, offer for sale, 427 | import and otherwise run, modify and propagate the contents of its contributor 428 | version. 429 | 430 | In the following three paragraphs, a “patent license” is any express 431 | agreement or commitment, however denominated, not to enforce a patent (such as an 432 | express permission to practice a patent or covenant not to sue for patent 433 | infringement). To “grant” such a patent license to a party means to make 434 | such an agreement or commitment not to enforce a patent against the party. 435 | 436 | If you convey a covered work, knowingly relying on a patent license, and the 437 | Corresponding Source of the work is not available for anyone to copy, free of charge 438 | and under the terms of this License, through a publicly available network server or 439 | other readily accessible means, then you must either (1) cause the Corresponding 440 | Source to be so available, or (2) arrange to deprive yourself of the benefit of the 441 | patent license for this particular work, or (3) arrange, in a manner consistent with 442 | the requirements of this License, to extend the patent license to downstream 443 | recipients. “Knowingly relying” means you have actual knowledge that, but 444 | for the patent license, your conveying the covered work in a country, or your 445 | recipient's use of the covered work in a country, would infringe one or more 446 | identifiable patents in that country that you have reason to believe are valid. 447 | 448 | If, pursuant to or in connection with a single transaction or arrangement, you 449 | convey, or propagate by procuring conveyance of, a covered work, and grant a patent 450 | license to some of the parties receiving the covered work authorizing them to use, 451 | propagate, modify or convey a specific copy of the covered work, then the patent 452 | license you grant is automatically extended to all recipients of the covered work and 453 | works based on it. 454 | 455 | A patent license is “discriminatory” if it does not include within the 456 | scope of its coverage, prohibits the exercise of, or is conditioned on the 457 | non-exercise of one or more of the rights that are specifically granted under this 458 | License. You may not convey a covered work if you are a party to an arrangement with 459 | a third party that is in the business of distributing software, under which you make 460 | payment to the third party based on the extent of your activity of conveying the 461 | work, and under which the third party grants, to any of the parties who would receive 462 | the covered work from you, a discriminatory patent license (a) in connection with 463 | copies of the covered work conveyed by you (or copies made from those copies), or (b) 464 | primarily for and in connection with specific products or compilations that contain 465 | the covered work, unless you entered into that arrangement, or that patent license 466 | was granted, prior to 28 March 2007. 467 | 468 | Nothing in this License shall be construed as excluding or limiting any implied 469 | license or other defenses to infringement that may otherwise be available to you 470 | under applicable patent law. 471 | 472 | ### 12. No Surrender of Others' Freedom. 473 | 474 | If conditions are imposed on you (whether by court order, agreement or otherwise) 475 | that contradict the conditions of this License, they do not excuse you from the 476 | conditions of this License. If you cannot convey a covered work so as to satisfy 477 | simultaneously your obligations under this License and any other pertinent 478 | obligations, then as a consequence you may not convey it at all. For example, if you 479 | agree to terms that obligate you to collect a royalty for further conveying from 480 | those to whom you convey the Program, the only way you could satisfy both those terms 481 | and this License would be to refrain entirely from conveying the Program. 482 | 483 | ### 13. Use with the GNU Affero General Public License. 484 | 485 | Notwithstanding any other provision of this License, you have permission to link or 486 | combine any covered work with a work licensed under version 3 of the GNU Affero 487 | General Public License into a single combined work, and to convey the resulting work. 488 | The terms of this License will continue to apply to the part which is the covered 489 | work, but the special requirements of the GNU Affero General Public License, section 490 | 13, concerning interaction through a network will apply to the combination as such. 491 | 492 | ### 14. Revised Versions of this License. 493 | 494 | The Free Software Foundation may publish revised and/or new versions of the GNU 495 | General Public License from time to time. Such new versions will be similar in spirit 496 | to the present version, but may differ in detail to address new problems or concerns. 497 | 498 | Each version is given a distinguishing version number. If the Program specifies that 499 | a certain numbered version of the GNU General Public License “or any later 500 | version” applies to it, you have the option of following the terms and 501 | conditions either of that numbered version or of any later version published by the 502 | Free Software Foundation. If the Program does not specify a version number of the GNU 503 | General Public License, you may choose any version ever published by the Free 504 | Software Foundation. 505 | 506 | If the Program specifies that a proxy can decide which future versions of the GNU 507 | General Public License can be used, that proxy's public statement of acceptance of a 508 | version permanently authorizes you to choose that version for the Program. 509 | 510 | Later license versions may give you additional or different permissions. However, no 511 | additional obligations are imposed on any author or copyright holder as a result of 512 | your choosing to follow a later version. 513 | 514 | ### 15. Disclaimer of Warranty. 515 | 516 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. 517 | EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES 518 | PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER 519 | EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 520 | MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE 521 | QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE 522 | DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 523 | 524 | ### 16. Limitation of Liability. 525 | 526 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY 527 | COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS 528 | PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, 529 | INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE 530 | PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE 531 | OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE 532 | WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 533 | POSSIBILITY OF SUCH DAMAGES. 534 | 535 | ### 17. Interpretation of Sections 15 and 16. 536 | 537 | If the disclaimer of warranty and limitation of liability provided above cannot be 538 | given local legal effect according to their terms, reviewing courts shall apply local 539 | law that most closely approximates an absolute waiver of all civil liability in 540 | connection with the Program, unless a warranty or assumption of liability accompanies 541 | a copy of the Program in return for a fee. 542 | 543 | END OF TERMS AND CONDITIONS 544 | 545 | ## How to Apply These Terms to Your New Programs 546 | 547 | If you develop a new program, and you want it to be of the greatest possible use to 548 | the public, the best way to achieve this is to make it free software which everyone 549 | can redistribute and change under these terms. 550 | 551 | To do so, attach the following notices to the program. It is safest to attach them 552 | to the start of each source file to most effectively state the exclusion of warranty; 553 | and each file should have at least the “copyright” line and a pointer to 554 | where the full notice is found. 555 | 556 | 557 | Copyright (C) 558 | 559 | This program is free software: you can redistribute it and/or modify 560 | it under the terms of the GNU General Public License as published by 561 | the Free Software Foundation, either version 3 of the License, or 562 | (at your option) any later version. 563 | 564 | This program is distributed in the hope that it will be useful, 565 | but WITHOUT ANY WARRANTY; without even the implied warranty of 566 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 567 | GNU General Public License for more details. 568 | 569 | You should have received a copy of the GNU General Public License 570 | along with this program. If not, see . 571 | 572 | Also add information on how to contact you by electronic and paper mail. 573 | 574 | If the program does terminal interaction, make it output a short notice like this 575 | when it starts in an interactive mode: 576 | 577 | Copyright (C) 578 | This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'. 579 | This is free software, and you are welcome to redistribute it 580 | under certain conditions; type 'show c' for details. 581 | 582 | The hypothetical commands 'show w' and 'show c' should show the appropriate parts of 583 | the General Public License. Of course, your program's commands might be different; 584 | for a GUI interface, you would use an “about box”. 585 | 586 | You should also get your employer (if you work as a programmer) or school, if any, to 587 | sign a “copyright disclaimer” for the program, if necessary. For more 588 | information on this, and how to apply and follow the GNU GPL, see 589 | <>. 590 | 591 | The GNU General Public License does not permit incorporating your program into 592 | proprietary programs. If your program is a subroutine library, you may consider it 593 | more useful to permit linking proprietary applications with the library. If this is 594 | what you want to do, use the GNU Lesser General Public License instead of this 595 | License. But first, please read 596 | <>. -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | obj-m := hellofs.o 2 | hellofs-objs := khellofs.o super.o inode.o dir.o file.o 3 | CFLAGS_khellofs.o := -DDEBUG 4 | CFLAGS_super.o := -DDEBUG 5 | CFLAGS_inode.o := -DDEBUG 6 | CFLAGS_dir.o := -DDEBUG 7 | CFLAGS_file.o := -DDEBUG 8 | 9 | all: ko mkfs-hellofs 10 | 11 | ko: 12 | make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules 13 | 14 | mkfs-hellofs_SOURCES: 15 | mkfs-hellofs.c hellofs.h 16 | 17 | clean: 18 | make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean 19 | rm mkfs-hellofs 20 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | 2 | Hellofs - An example kernel filesystem implementation 3 | === 4 | 5 | A very simple linux kernel filesystem for learning purpose. It demonstrates how to implement a VFS filesystem, from superblock, inode, dir to file operations. The license is GPL because some kernel functions require it to be available. 6 | 7 | Hellofs is written and tested on Centos 7.1.1503 kernel [3.10.0-229.1.2.el7.x86_64](http://lxr.free-electrons.com/source/?v=3.10). Note that from kernel version 3.11 some code related to dir operations are changed, for example [readdir](https://github.com/psankar/simplefs/blob/5d00eebd45ff9402848acfbbdbad4282393dd60a/simple.c#L212). It is rewritten based on Sankar's [Simplefs (commit 5d00eebd)](https://github.com/psankar/simplefs/tree/5d00eebd45ff9402848acfbbdbad4282393dd60a)). Thanks to the greate [Simplefs](https://github.com/psankar/simplefs)! Actually I found most resources about writting kernel FS are outdated (they are always talking about 2.6). But kernel is being developed in such rapid pace (it is 4.x now!). An working example is precious! 8 | 9 | Major modifications that I made on Simplefs are 10 | 11 | * Total overhaul of the code structure to make them easier to understand. 12 | * Removed journal ([jbd2](https://github.com/psankar/simplefs/blob/5d00eebd45ff9402848acfbbdbad4282393dd60a/simple.c#L18)) related code since my kernel build doesn't support them. 13 | * Use bitmap to allocate inodes and data blocks, which should be more scalable. 14 | 15 | The on-disk layout of Hellofs is 16 | 17 | * superblock (1 block) 18 | * inode bitmap (1 block) 19 | * data block bitmap (1 block) 20 | * inode table (variable length) 21 | * data block table (variable length) 22 | 23 | One disk block contains multiple inodes. One data block corresponds to one disk block (and of the same size). Each inode contains only one data block for simplicity. 24 | 25 | To run test cases 26 | 27 | ``` 28 | cd hellofs 29 | sudo ./hellofs-test.sh | grep "Test finished successfully" 30 | ``` 31 | 32 | -------------------------------------------------------------------------------- /dir.c: -------------------------------------------------------------------------------- 1 | #include "khellofs.h" 2 | 3 | int hellofs_readdir(struct file *filp, void *dirent, filldir_t filldir) { 4 | loff_t pos; 5 | struct inode *inode; 6 | struct super_block *sb; 7 | struct buffer_head *bh; 8 | struct hellofs_inode *hellofs_inode; 9 | struct hellofs_dir_record *dir_record; 10 | uint64_t i; 11 | 12 | pos = filp->f_pos; 13 | inode = filp->f_dentry->d_inode; 14 | sb = inode->i_sb; 15 | hellofs_inode = HELLOFS_INODE(inode); 16 | 17 | if (pos) { 18 | // TODO @Sankar: we use a hack of reading pos to figure if we have filled in data. 19 | return 0; 20 | } 21 | 22 | printk(KERN_INFO "readdir: hellofs_inode->inode_no=%llu", hellofs_inode->inode_no); 23 | 24 | if (unlikely(!S_ISDIR(hellofs_inode->mode))) { 25 | printk(KERN_ERR 26 | "Inode %llu of dentry %s is not a directory\n", 27 | hellofs_inode->inode_no, 28 | filp->f_dentry->d_name.name); 29 | return -ENOTDIR; 30 | } 31 | 32 | bh = sb_bread(sb, hellofs_inode->data_block_no); 33 | BUG_ON(!bh); 34 | 35 | dir_record = (struct hellofs_dir_record *)bh->b_data; 36 | for (i = 0; i < hellofs_inode->dir_children_count; i++) { 37 | filldir(dirent, dir_record->filename, HELLOFS_FILENAME_MAXLEN, pos, 38 | dir_record->inode_no, DT_UNKNOWN); 39 | filp->f_pos += sizeof(struct hellofs_dir_record); 40 | pos += sizeof(struct hellofs_dir_record); 41 | dir_record++; 42 | } 43 | brelse(bh); 44 | 45 | return 0; 46 | } 47 | -------------------------------------------------------------------------------- /file.c: -------------------------------------------------------------------------------- 1 | #include "khellofs.h" 2 | 3 | ssize_t hellofs_read(struct file *filp, char __user *buf, size_t len, 4 | loff_t *ppos) { 5 | struct super_block *sb; 6 | struct inode *inode; 7 | struct hellofs_inode *hellofs_inode; 8 | struct buffer_head *bh; 9 | char *buffer; 10 | int nbytes; 11 | 12 | inode = filp->f_path.dentry->d_inode; 13 | sb = inode->i_sb; 14 | hellofs_inode = HELLOFS_INODE(inode); 15 | 16 | if (*ppos >= hellofs_inode->file_size) { 17 | return 0; 18 | } 19 | 20 | bh = sb_bread(sb, hellofs_inode->data_block_no); 21 | if (!bh) { 22 | printk(KERN_ERR "Failed to read data block %llu\n", 23 | hellofs_inode->data_block_no); 24 | return 0; 25 | } 26 | 27 | buffer = (char *)bh->b_data + *ppos; 28 | nbytes = min((size_t)(hellofs_inode->file_size - *ppos), len); 29 | 30 | if (copy_to_user(buf, buffer, nbytes)) { 31 | brelse(bh); 32 | printk(KERN_ERR 33 | "Error copying file content to userspace buffer\n"); 34 | return -EFAULT; 35 | } 36 | 37 | brelse(bh); 38 | *ppos += nbytes; 39 | return nbytes; 40 | } 41 | 42 | /* TODO We didn't use address_space/pagecache here. 43 | If we hook file_operations.write = do_sync_write, 44 | and file_operations.aio_write = generic_file_aio_write, 45 | we will use write to pagecache instead. */ 46 | ssize_t hellofs_write(struct file *filp, const char __user *buf, size_t len, 47 | loff_t *ppos) { 48 | struct super_block *sb; 49 | struct inode *inode; 50 | struct hellofs_inode *hellofs_inode; 51 | struct buffer_head *bh; 52 | struct hellofs_superblock *hellofs_sb; 53 | char *buffer; 54 | int ret; 55 | 56 | inode = filp->f_path.dentry->d_inode; 57 | sb = inode->i_sb; 58 | hellofs_inode = HELLOFS_INODE(inode); 59 | hellofs_sb = HELLOFS_SB(sb); 60 | 61 | ret = generic_write_checks(filp, ppos, &len, 0); 62 | if (ret) { 63 | return ret; 64 | } 65 | 66 | bh = sb_bread(sb, hellofs_inode->data_block_no); 67 | if (!bh) { 68 | printk(KERN_ERR "Failed to read data block %llu\n", 69 | hellofs_inode->data_block_no); 70 | return 0; 71 | } 72 | 73 | buffer = (char *)bh->b_data + *ppos; 74 | if (copy_from_user(buffer, buf, len)) { 75 | brelse(bh); 76 | printk(KERN_ERR 77 | "Error copying file content from userspace buffer " 78 | "to kernel space\n"); 79 | return -EFAULT; 80 | } 81 | *ppos += len; 82 | 83 | mark_buffer_dirty(bh); 84 | sync_dirty_buffer(bh); 85 | brelse(bh); 86 | 87 | hellofs_inode->file_size = max((size_t)(hellofs_inode->file_size), 88 | (size_t)(*ppos)); 89 | hellofs_save_hellofs_inode(sb, hellofs_inode); 90 | 91 | /* TODO We didn't update file size here. To be frank I don't know how. */ 92 | 93 | return len; 94 | } 95 | -------------------------------------------------------------------------------- /hellofs-test.sh: -------------------------------------------------------------------------------- 1 | #!/bin/bash 2 | 3 | set -e 4 | 5 | root_pwd="$PWD" 6 | test_dir="test-dir-$RANDOM" 7 | test_mount_point="test-mount-point-$RANDOM" 8 | 9 | function create_test_image() { 10 | dd bs=4096 count=6000 if=/dev/zero of="$1" 11 | ./mkfs-hellofs "$1" 12 | } 13 | 14 | function mount_fs_image() { 15 | insmod ./hellofs.ko 16 | mount -o loop,owner,group,users -t hellofs "$1" "$2" 17 | } 18 | 19 | function unmount_fs() { 20 | umount "$1" 21 | rmmod ./hellofs.ko 22 | } 23 | 24 | function do_some_operations() { 25 | cd "$1" 26 | 27 | ls 28 | cat wel_helo.txt 29 | 30 | cp wel_helo.txt hello 31 | cat hello 32 | 33 | echo "Hello World" > hello 34 | cat hello 35 | 36 | mkdir dir1 && cd dir1 37 | 38 | cp ../hello . 39 | cat hello 40 | 41 | echo "First level directory" > hello 42 | cat hello 43 | 44 | mkdir dir2 && cd dir2 45 | 46 | touch hello 47 | cat hello 48 | 49 | echo "Second level directory" > hello 50 | cat hello 51 | 52 | cp hello hello_smaller 53 | echo "smaller" > hello_smaller 54 | cat hello_smaller 55 | } 56 | 57 | function do_read_operations() 58 | { 59 | cd "$1" 60 | ls -lR 61 | 62 | cat wel_helo.txt 63 | cat hello 64 | 65 | cat hello 66 | 67 | cd dir1 68 | cat hello 69 | 70 | cd dir2 71 | cat hello 72 | cat hello_smaller 73 | } 74 | 75 | function cleanup() { 76 | cd "$root_pwd" 77 | mount | grep -q "$test_mount_point" && umount -t hellofs "$test_mount_point" 78 | lsmod | grep -q hellofs && rmmod "$root_pwd/hellofs.ko" 79 | rm -fR "$test_dir" "$test_mount_point" 80 | } 81 | 82 | set -x 83 | make 84 | 85 | cleanup 86 | trap cleanup SIGINT EXIT 87 | mkdir "$test_dir" "$test_mount_point" 88 | create_test_image "$test_dir/image" 89 | 90 | # run 1 91 | mount_fs_image "$test_dir/image" "$test_mount_point" 92 | do_some_operations "$test_mount_point" 93 | cd "$root_pwd" 94 | unmount_fs "$test_mount_point" 95 | 96 | # run 2 97 | mount_fs_image "$test_dir/image" "$test_mount_point" 98 | do_read_operations "$test_mount_point" 99 | cd "$root_pwd" 100 | ls -lR "$test_mount_point" 101 | unmount_fs "$test_mount_point" 102 | 103 | echo "Test finished successfully!" 104 | cleanup 105 | 106 | make clean 107 | rm -rf "$test_dir/image" "$test_mount_point" 108 | -------------------------------------------------------------------------------- /hellofs.h: -------------------------------------------------------------------------------- 1 | #ifndef __HELLOFS_H__ 2 | #define __HELLOFS_H__ 3 | 4 | #define BITS_IN_BYTE 8 5 | #define HELLOFS_MAGIC 0x20160105 6 | #define HELLOFS_DEFAULT_BLOCKSIZE 4096 7 | #define HELLOFS_DEFAULT_INODE_TABLE_SIZE 1024 8 | #define HELLOFS_DEFAULT_DATA_BLOCK_TABLE_SIZE 1024 9 | #define HELLOFS_FILENAME_MAXLEN 255 10 | 11 | /* Define filesystem structures */ 12 | 13 | extern struct mutex hellofs_sb_lock; 14 | 15 | struct hellofs_dir_record { 16 | char filename[HELLOFS_FILENAME_MAXLEN]; 17 | uint64_t inode_no; 18 | }; 19 | 20 | struct hellofs_inode { 21 | mode_t mode; 22 | uint64_t inode_no; 23 | uint64_t data_block_no; 24 | 25 | // TODO struct timespec is defined kenrel space, 26 | // but mkfs-hellofs.c is compiled in user space 27 | /*struct timespec atime; 28 | struct timespec mtime; 29 | struct timespec ctime;*/ 30 | 31 | union { 32 | uint64_t file_size; 33 | uint64_t dir_children_count; 34 | }; 35 | }; 36 | 37 | struct hellofs_superblock { 38 | uint64_t version; 39 | uint64_t magic; 40 | uint64_t blocksize; 41 | 42 | uint64_t inode_table_size; 43 | uint64_t inode_count; 44 | 45 | uint64_t data_block_table_size; 46 | uint64_t data_block_count; 47 | }; 48 | 49 | static const uint64_t HELLOFS_SUPERBLOCK_BLOCK_NO = 0; 50 | static const uint64_t HELLOFS_INODE_BITMAP_BLOCK_NO = 1; 51 | static const uint64_t HELLOFS_DATA_BLOCK_BITMAP_BLOCK_NO = 2; 52 | static const uint64_t HELLOFS_INODE_TABLE_START_BLOCK_NO = 3; 53 | 54 | static const uint64_t HELLOFS_ROOTDIR_INODE_NO = 0; 55 | // data block no is the absolute block number from start of device 56 | // data block no offset is the relative block offset from start of data block table 57 | static const uint64_t HELLOFS_ROOTDIR_DATA_BLOCK_NO_OFFSET = 0; 58 | 59 | /* Helper functions */ 60 | 61 | static inline uint64_t HELLOFS_INODES_PER_BLOCK_HSB( 62 | struct hellofs_superblock *hellofs_sb) { 63 | return hellofs_sb->blocksize / sizeof(struct hellofs_inode); 64 | } 65 | 66 | static inline uint64_t HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB( 67 | struct hellofs_superblock *hellofs_sb) { 68 | return HELLOFS_INODE_TABLE_START_BLOCK_NO 69 | + hellofs_sb->inode_table_size / HELLOFS_INODES_PER_BLOCK_HSB(hellofs_sb) 70 | + 1; 71 | } 72 | 73 | #endif /*__HELLOFS_H__*/ -------------------------------------------------------------------------------- /inode.c: -------------------------------------------------------------------------------- 1 | #include "khellofs.h" 2 | 3 | void hellofs_destroy_inode(struct inode *inode) { 4 | struct hellofs_inode *hellofs_inode = HELLOFS_INODE(inode); 5 | 6 | printk(KERN_INFO "Freeing private data of inode %p (%lu)\n", 7 | hellofs_inode, inode->i_ino); 8 | kmem_cache_free(hellofs_inode_cache, hellofs_inode); 9 | } 10 | 11 | void hellofs_fill_inode(struct super_block *sb, struct inode *inode, 12 | struct hellofs_inode *hellofs_inode) { 13 | inode->i_mode = hellofs_inode->mode; 14 | inode->i_sb = sb; 15 | inode->i_ino = hellofs_inode->inode_no; 16 | inode->i_op = &hellofs_inode_ops; 17 | // TODO hope we can use hellofs_inode to store timespec 18 | inode->i_atime = inode->i_mtime 19 | = inode->i_ctime 20 | = CURRENT_TIME; 21 | inode->i_private = hellofs_inode; 22 | 23 | if (S_ISDIR(hellofs_inode->mode)) { 24 | inode->i_fop = &hellofs_dir_operations; 25 | } else if (S_ISREG(hellofs_inode->mode)) { 26 | inode->i_fop = &hellofs_file_operations; 27 | } else { 28 | printk(KERN_WARNING 29 | "Inode %lu is neither a directory nor a regular file", 30 | inode->i_ino); 31 | inode->i_fop = NULL; 32 | } 33 | 34 | /* TODO hellofs_inode->file_size seems not reflected in inode */ 35 | } 36 | 37 | /* TODO I didn't implement any function to dealloc hellofs_inode */ 38 | int hellofs_alloc_hellofs_inode(struct super_block *sb, uint64_t *out_inode_no) { 39 | struct hellofs_superblock *hellofs_sb; 40 | struct buffer_head *bh; 41 | uint64_t i; 42 | int ret; 43 | char *bitmap; 44 | char *slot; 45 | char needle; 46 | 47 | hellofs_sb = HELLOFS_SB(sb); 48 | 49 | mutex_lock(&hellofs_sb_lock); 50 | 51 | bh = sb_bread(sb, HELLOFS_INODE_BITMAP_BLOCK_NO); 52 | BUG_ON(!bh); 53 | 54 | bitmap = bh->b_data; 55 | ret = -ENOSPC; 56 | for (i = 0; i < hellofs_sb->inode_table_size; i++) { 57 | slot = bitmap + i / BITS_IN_BYTE; 58 | needle = 1 << (i % BITS_IN_BYTE); 59 | if (0 == (*slot & needle)) { 60 | *out_inode_no = i; 61 | *slot |= needle; 62 | hellofs_sb->inode_count += 1; 63 | ret = 0; 64 | break; 65 | } 66 | } 67 | 68 | mark_buffer_dirty(bh); 69 | sync_dirty_buffer(bh); 70 | brelse(bh); 71 | hellofs_save_sb(sb); 72 | 73 | mutex_unlock(&hellofs_sb_lock); 74 | return ret; 75 | } 76 | 77 | struct hellofs_inode *hellofs_get_hellofs_inode(struct super_block *sb, 78 | uint64_t inode_no) { 79 | struct buffer_head *bh; 80 | struct hellofs_inode *inode; 81 | struct hellofs_inode *inode_buf; 82 | 83 | bh = sb_bread(sb, HELLOFS_INODE_TABLE_START_BLOCK_NO + HELLOFS_INODE_BLOCK_OFFSET(sb, inode_no)); 84 | BUG_ON(!bh); 85 | 86 | inode = (struct hellofs_inode *)(bh->b_data + HELLOFS_INODE_BYTE_OFFSET(sb, inode_no)); 87 | inode_buf = kmem_cache_alloc(hellofs_inode_cache, GFP_KERNEL); 88 | memcpy(inode_buf, inode, sizeof(*inode_buf)); 89 | 90 | brelse(bh); 91 | return inode_buf; 92 | } 93 | 94 | void hellofs_save_hellofs_inode(struct super_block *sb, 95 | struct hellofs_inode *inode_buf) { 96 | struct buffer_head *bh; 97 | struct hellofs_inode *inode; 98 | uint64_t inode_no; 99 | 100 | inode_no = inode_buf->inode_no; 101 | bh = sb_bread(sb, HELLOFS_INODE_TABLE_START_BLOCK_NO + HELLOFS_INODE_BLOCK_OFFSET(sb, inode_no)); 102 | BUG_ON(!bh); 103 | 104 | inode = (struct hellofs_inode *)(bh->b_data + HELLOFS_INODE_BYTE_OFFSET(sb, inode_no)); 105 | memcpy(inode, inode_buf, sizeof(*inode)); 106 | 107 | mark_buffer_dirty(bh); 108 | sync_dirty_buffer(bh); 109 | brelse(bh); 110 | } 111 | 112 | int hellofs_add_dir_record(struct super_block *sb, struct inode *dir, 113 | struct dentry *dentry, struct inode *inode) { 114 | struct buffer_head *bh; 115 | struct hellofs_inode *parent_hellofs_inode; 116 | struct hellofs_dir_record *dir_record; 117 | 118 | parent_hellofs_inode = HELLOFS_INODE(dir); 119 | if (unlikely(parent_hellofs_inode->dir_children_count 120 | >= HELLOFS_DIR_MAX_RECORD(sb))) { 121 | return -ENOSPC; 122 | } 123 | 124 | bh = sb_bread(sb, parent_hellofs_inode->data_block_no); 125 | BUG_ON(!bh); 126 | 127 | dir_record = (struct hellofs_dir_record *)bh->b_data; 128 | dir_record += parent_hellofs_inode->dir_children_count; 129 | dir_record->inode_no = inode->i_ino; 130 | strcpy(dir_record->filename, dentry->d_name.name); 131 | 132 | mark_buffer_dirty(bh); 133 | sync_dirty_buffer(bh); 134 | brelse(bh); 135 | 136 | parent_hellofs_inode->dir_children_count += 1; 137 | hellofs_save_hellofs_inode(sb, parent_hellofs_inode); 138 | 139 | return 0; 140 | } 141 | 142 | int hellofs_alloc_data_block(struct super_block *sb, uint64_t *out_data_block_no) { 143 | struct hellofs_superblock *hellofs_sb; 144 | struct buffer_head *bh; 145 | uint64_t i; 146 | int ret; 147 | char *bitmap; 148 | char *slot; 149 | char needle; 150 | 151 | hellofs_sb = HELLOFS_SB(sb); 152 | 153 | mutex_lock(&hellofs_sb_lock); 154 | 155 | bh = sb_bread(sb, HELLOFS_DATA_BLOCK_BITMAP_BLOCK_NO); 156 | BUG_ON(!bh); 157 | 158 | bitmap = bh->b_data; 159 | ret = -ENOSPC; 160 | for (i = 0; i < hellofs_sb->data_block_table_size; i++) { 161 | slot = bitmap + i / BITS_IN_BYTE; 162 | needle = 1 << (i % BITS_IN_BYTE); 163 | if (0 == (*slot & needle)) { 164 | *out_data_block_no 165 | = HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO(sb) + i; 166 | *slot |= needle; 167 | hellofs_sb->data_block_count += 1; 168 | ret = 0; 169 | break; 170 | } 171 | } 172 | 173 | mark_buffer_dirty(bh); 174 | sync_dirty_buffer(bh); 175 | brelse(bh); 176 | hellofs_save_sb(sb); 177 | 178 | mutex_unlock(&hellofs_sb_lock); 179 | return ret; 180 | } 181 | 182 | int hellofs_create_inode(struct inode *dir, struct dentry *dentry, 183 | umode_t mode) { 184 | struct super_block *sb; 185 | struct hellofs_superblock *hellofs_sb; 186 | uint64_t inode_no; 187 | struct hellofs_inode *hellofs_inode; 188 | struct inode *inode; 189 | int ret; 190 | 191 | sb = dir->i_sb; 192 | hellofs_sb = HELLOFS_SB(sb); 193 | 194 | /* Create hellofs_inode */ 195 | ret = hellofs_alloc_hellofs_inode(sb, &inode_no); 196 | if (0 != ret) { 197 | printk(KERN_ERR "Unable to allocate on-disk inode. " 198 | "Is inode table full? " 199 | "Inode count: %llu\n", 200 | hellofs_sb->inode_count); 201 | return -ENOSPC; 202 | } 203 | hellofs_inode = kmem_cache_alloc(hellofs_inode_cache, GFP_KERNEL); 204 | hellofs_inode->inode_no = inode_no; 205 | hellofs_inode->mode = mode; 206 | if (S_ISDIR(mode)) { 207 | hellofs_inode->dir_children_count = 0; 208 | } else if (S_ISREG(mode)) { 209 | hellofs_inode->file_size = 0; 210 | } else { 211 | printk(KERN_WARNING 212 | "Inode %llu is neither a directory nor a regular file", 213 | inode_no); 214 | } 215 | 216 | /* Allocate data block for the new hellofs_inode */ 217 | ret = hellofs_alloc_data_block(sb, &hellofs_inode->data_block_no); 218 | if (0 != ret) { 219 | printk(KERN_ERR "Unable to allocate on-disk data block. " 220 | "Is data block table full? " 221 | "Data block count: %llu\n", 222 | hellofs_sb->data_block_count); 223 | return -ENOSPC; 224 | } 225 | 226 | /* Create VFS inode */ 227 | inode = new_inode(sb); 228 | if (!inode) { 229 | return -ENOMEM; 230 | } 231 | hellofs_fill_inode(sb, inode, hellofs_inode); 232 | 233 | /* Add new inode to parent dir */ 234 | ret = hellofs_add_dir_record(sb, dir, dentry, inode); 235 | if (0 != ret) { 236 | printk(KERN_ERR "Failed to add inode %lu to parent dir %lu\n", 237 | inode->i_ino, dir->i_ino); 238 | return -ENOSPC; 239 | } 240 | 241 | inode_init_owner(inode, dir, mode); 242 | d_add(dentry, inode); 243 | 244 | /* TODO we should free newly allocated inodes when error occurs */ 245 | 246 | return 0; 247 | } 248 | 249 | int hellofs_create(struct inode *dir, struct dentry *dentry, 250 | umode_t mode, bool excl) { 251 | return hellofs_create_inode(dir, dentry, mode); 252 | } 253 | 254 | int hellofs_mkdir(struct inode *dir, struct dentry *dentry, 255 | umode_t mode) { 256 | /* @Sankar: The mkdir callback does not have S_IFDIR set. 257 | Even ext2 sets it explicitly. Perhaps this is a bug */ 258 | mode |= S_IFDIR; 259 | return hellofs_create_inode(dir, dentry, mode); 260 | } 261 | 262 | struct dentry *hellofs_lookup(struct inode *dir, 263 | struct dentry *child_dentry, 264 | unsigned int flags) { 265 | struct hellofs_inode *parent_hellofs_inode = HELLOFS_INODE(dir); 266 | struct super_block *sb = dir->i_sb; 267 | struct buffer_head *bh; 268 | struct hellofs_dir_record *dir_record; 269 | struct hellofs_inode *hellofs_child_inode; 270 | struct inode *child_inode; 271 | uint64_t i; 272 | 273 | bh = sb_bread(sb, parent_hellofs_inode->data_block_no); 274 | BUG_ON(!bh); 275 | 276 | dir_record = (struct hellofs_dir_record *)bh->b_data; 277 | 278 | for (i = 0; i < parent_hellofs_inode->dir_children_count; i++) { 279 | printk(KERN_INFO "hellofs_lookup: i=%llu, dir_record->filename=%s, child_dentry->d_name.name=%s", i, dir_record->filename, child_dentry->d_name.name); // TODO 280 | if (0 == strcmp(dir_record->filename, child_dentry->d_name.name)) { 281 | hellofs_child_inode = hellofs_get_hellofs_inode(sb, dir_record->inode_no); 282 | child_inode = new_inode(sb); 283 | if (!child_inode) { 284 | printk(KERN_ERR "Cannot create new inode. No memory.\n"); 285 | return NULL; 286 | } 287 | hellofs_fill_inode(sb, child_inode, hellofs_child_inode); 288 | inode_init_owner(child_inode, dir, hellofs_child_inode->mode); 289 | d_add(child_dentry, child_inode); 290 | return NULL; 291 | } 292 | dir_record++; 293 | } 294 | 295 | printk(KERN_ERR 296 | "No inode found for the filename: %s\n", 297 | child_dentry->d_name.name); 298 | return NULL; 299 | } -------------------------------------------------------------------------------- /khellofs.c: -------------------------------------------------------------------------------- 1 | #include "khellofs.h" 2 | 3 | DEFINE_MUTEX(hellofs_sb_lock); 4 | 5 | struct file_system_type hellofs_fs_type = { 6 | .owner = THIS_MODULE, 7 | .name = "hellofs", 8 | .mount = hellofs_mount, 9 | .kill_sb = hellofs_kill_superblock, 10 | .fs_flags = FS_REQUIRES_DEV, 11 | }; 12 | 13 | const struct super_operations hellofs_sb_ops = { 14 | .destroy_inode = hellofs_destroy_inode, 15 | .put_super = hellofs_put_super, 16 | }; 17 | 18 | const struct inode_operations hellofs_inode_ops = { 19 | .create = hellofs_create, 20 | .mkdir = hellofs_mkdir, 21 | .lookup = hellofs_lookup, 22 | }; 23 | 24 | const struct file_operations hellofs_dir_operations = { 25 | .owner = THIS_MODULE, 26 | .readdir = hellofs_readdir, 27 | }; 28 | 29 | const struct file_operations hellofs_file_operations = { 30 | .read = hellofs_read, 31 | .write = hellofs_write, 32 | }; 33 | 34 | struct kmem_cache *hellofs_inode_cache = NULL; 35 | 36 | static int __init hellofs_init(void) 37 | { 38 | int ret; 39 | 40 | hellofs_inode_cache = kmem_cache_create("hellofs_inode_cache", 41 | sizeof(struct hellofs_inode), 42 | 0, 43 | (SLAB_RECLAIM_ACCOUNT| SLAB_MEM_SPREAD), 44 | NULL); 45 | if (!hellofs_inode_cache) { 46 | return -ENOMEM; 47 | } 48 | 49 | ret = register_filesystem(&hellofs_fs_type); 50 | if (likely(0 == ret)) { 51 | printk(KERN_INFO "Sucessfully registered hellofs\n"); 52 | } else { 53 | printk(KERN_ERR "Failed to register hellofs. Error code: %d\n", ret); 54 | } 55 | 56 | return ret; 57 | } 58 | 59 | static void __exit hellofs_exit(void) 60 | { 61 | int ret; 62 | 63 | ret = unregister_filesystem(&hellofs_fs_type); 64 | kmem_cache_destroy(hellofs_inode_cache); 65 | 66 | if (likely(ret == 0)) { 67 | printk(KERN_INFO "Sucessfully unregistered hellofs\n"); 68 | } else { 69 | printk(KERN_ERR "Failed to unregister hellofs. Error code: %d\n", 70 | ret); 71 | } 72 | } 73 | 74 | module_init(hellofs_init); 75 | module_exit(hellofs_exit); 76 | 77 | MODULE_LICENSE("GPL"); 78 | MODULE_AUTHOR("accelazh"); 79 | -------------------------------------------------------------------------------- /khellofs.h: -------------------------------------------------------------------------------- 1 | #ifndef __KHELLOFS_H__ 2 | #define __KHELLOFS_H__ 3 | 4 | /* khellofs.h defines symbols to work in kernel space */ 5 | 6 | #include 7 | #include 8 | #include 9 | #include 10 | #include 11 | #include 12 | #include 13 | #include 14 | #include 15 | #include 16 | #include 17 | 18 | #include "hellofs.h" 19 | 20 | /* Declare operations to be hooked to VFS */ 21 | 22 | extern struct file_system_type hellofs_fs_type; 23 | extern const struct super_operations hellofs_sb_ops; 24 | extern const struct inode_operations hellofs_inode_ops; 25 | extern const struct file_operations hellofs_dir_operations; 26 | extern const struct file_operations hellofs_file_operations; 27 | 28 | struct dentry *hellofs_mount(struct file_system_type *fs_type, 29 | int flags, const char *dev_name, 30 | void *data); 31 | void hellofs_kill_superblock(struct super_block *sb); 32 | 33 | void hellofs_destroy_inode(struct inode *inode); 34 | void hellofs_put_super(struct super_block *sb); 35 | 36 | int hellofs_create(struct inode *dir, struct dentry *dentry, 37 | umode_t mode, bool excl); 38 | struct dentry *hellofs_lookup(struct inode *parent_inode, 39 | struct dentry *child_dentry, 40 | unsigned int flags); 41 | int hellofs_mkdir(struct inode *dir, struct dentry *dentry, 42 | umode_t mode); 43 | 44 | int hellofs_readdir(struct file *filp, void *dirent, filldir_t filldir); 45 | 46 | ssize_t hellofs_read(struct file * filp, char __user * buf, size_t len, 47 | loff_t * ppos); 48 | ssize_t hellofs_write(struct file * filp, const char __user * buf, size_t len, 49 | loff_t * ppos); 50 | 51 | extern struct kmem_cache *hellofs_inode_cache; 52 | 53 | /* Helper functions */ 54 | 55 | // To translate VFS superblock to hellofs superblock 56 | static inline struct hellofs_superblock *HELLOFS_SB(struct super_block *sb) { 57 | return sb->s_fs_info; 58 | } 59 | static inline struct hellofs_inode *HELLOFS_INODE(struct inode *inode) { 60 | return inode->i_private; 61 | } 62 | 63 | static inline uint64_t HELLOFS_INODES_PER_BLOCK(struct super_block *sb) { 64 | struct hellofs_superblock *hellofs_sb; 65 | hellofs_sb = HELLOFS_SB(sb); 66 | return HELLOFS_INODES_PER_BLOCK_HSB(hellofs_sb); 67 | } 68 | 69 | // Given the inode_no, calcuate which block in inode table contains the corresponding inode 70 | static inline uint64_t HELLOFS_INODE_BLOCK_OFFSET(struct super_block *sb, uint64_t inode_no) { 71 | struct hellofs_superblock *hellofs_sb; 72 | hellofs_sb = HELLOFS_SB(sb); 73 | return inode_no / HELLOFS_INODES_PER_BLOCK_HSB(hellofs_sb); 74 | } 75 | static inline uint64_t HELLOFS_INODE_BYTE_OFFSET(struct super_block *sb, uint64_t inode_no) { 76 | struct hellofs_superblock *hellofs_sb; 77 | hellofs_sb = HELLOFS_SB(sb); 78 | return (inode_no % HELLOFS_INODES_PER_BLOCK_HSB(hellofs_sb)) * sizeof(struct hellofs_inode); 79 | } 80 | 81 | static inline uint64_t HELLOFS_DIR_MAX_RECORD(struct super_block *sb) { 82 | struct hellofs_superblock *hellofs_sb; 83 | hellofs_sb = HELLOFS_SB(sb); 84 | return hellofs_sb->blocksize / sizeof(struct hellofs_dir_record); 85 | } 86 | 87 | // From which block does data blocks start 88 | static inline uint64_t HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO(struct super_block *sb) { 89 | struct hellofs_superblock *hellofs_sb; 90 | hellofs_sb = HELLOFS_SB(sb); 91 | return HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB(hellofs_sb); 92 | } 93 | 94 | void hellofs_save_sb(struct super_block *sb); 95 | 96 | // functions to operate inode 97 | void hellofs_fill_inode(struct super_block *sb, struct inode *inode, 98 | struct hellofs_inode *hellofs_inode); 99 | int hellofs_alloc_hellofs_inode(struct super_block *sb, uint64_t *out_inode_no); 100 | struct hellofs_inode *hellofs_get_hellofs_inode(struct super_block *sb, 101 | uint64_t inode_no); 102 | void hellofs_save_hellofs_inode(struct super_block *sb, 103 | struct hellofs_inode *inode); 104 | int hellofs_add_dir_record(struct super_block *sb, struct inode *dir, 105 | struct dentry *dentry, struct inode *inode); 106 | int hellofs_alloc_data_block(struct super_block *sb, uint64_t *out_data_block_no); 107 | int hellofs_create_inode(struct inode *dir, struct dentry *dentry, 108 | umode_t mode); 109 | 110 | #endif /*__KHELLOFS_H__*/ -------------------------------------------------------------------------------- /mkfs-hellofs.c: -------------------------------------------------------------------------------- 1 | #include 2 | #include 3 | #include 4 | #include 5 | #include 6 | #include 7 | #include 8 | #include 9 | 10 | #include "hellofs.h" 11 | 12 | int main(int argc, char *argv[]) { 13 | int fd; 14 | ssize_t ret; 15 | uint64_t welcome_inode_no; 16 | uint64_t welcome_data_block_no_offset; 17 | 18 | fd = open(argv[1], O_RDWR); 19 | if (fd == -1) { 20 | perror("Error opening the device"); 21 | return -1; 22 | } 23 | 24 | // construct superblock 25 | struct hellofs_superblock hellofs_sb = { 26 | .version = 1, 27 | .magic = HELLOFS_MAGIC, 28 | .blocksize = HELLOFS_DEFAULT_BLOCKSIZE, 29 | .inode_table_size = HELLOFS_DEFAULT_INODE_TABLE_SIZE, 30 | .inode_count = 2, 31 | .data_block_table_size = HELLOFS_DEFAULT_DATA_BLOCK_TABLE_SIZE, 32 | .data_block_count = 2, 33 | }; 34 | 35 | // construct inode bitmap 36 | char inode_bitmap[hellofs_sb.blocksize]; 37 | memset(inode_bitmap, 0, sizeof(inode_bitmap)); 38 | inode_bitmap[0] = 1; 39 | 40 | // construct data block bitmap 41 | char data_block_bitmap[hellofs_sb.blocksize]; 42 | memset(data_block_bitmap, 0, sizeof(data_block_bitmap)); 43 | data_block_bitmap[0] = 1; 44 | 45 | // construct root inode 46 | struct hellofs_inode root_hellofs_inode = { 47 | .mode = S_IFDIR | S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH, 48 | .inode_no = HELLOFS_ROOTDIR_INODE_NO, 49 | .data_block_no 50 | = HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB(&hellofs_sb) 51 | + HELLOFS_ROOTDIR_DATA_BLOCK_NO_OFFSET, 52 | .dir_children_count = 1, 53 | }; 54 | 55 | // construct welcome file inode 56 | char welcome_body[] = "Welcome Hellofs!!\n"; 57 | welcome_inode_no = HELLOFS_ROOTDIR_INODE_NO + 1; 58 | welcome_data_block_no_offset = HELLOFS_ROOTDIR_DATA_BLOCK_NO_OFFSET + 1; 59 | struct hellofs_inode welcome_hellofs_inode = { 60 | .mode = S_IFREG | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH, 61 | .inode_no = welcome_inode_no, 62 | .data_block_no 63 | = HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB(&hellofs_sb) 64 | + welcome_data_block_no_offset, 65 | .file_size = sizeof(welcome_body), 66 | }; 67 | 68 | // construct root inode data block 69 | struct hellofs_dir_record root_dir_records[] = { 70 | { 71 | .filename = "wel_helo.txt", 72 | .inode_no = welcome_inode_no, 73 | }, 74 | }; 75 | 76 | ret = 0; 77 | do { 78 | // write super block 79 | if (sizeof(hellofs_sb) 80 | != write(fd, &hellofs_sb, sizeof(hellofs_sb))) { 81 | ret = -1; 82 | break; 83 | } 84 | if ((off_t)-1 85 | == lseek(fd, hellofs_sb.blocksize, SEEK_SET)) { 86 | ret = -2; 87 | break; 88 | } 89 | 90 | // write inode bitmap 91 | if (sizeof(inode_bitmap) 92 | != write(fd, inode_bitmap, sizeof(inode_bitmap))) { 93 | ret = -3; 94 | break; 95 | } 96 | 97 | // write data block bitmap 98 | if (sizeof(data_block_bitmap) 99 | != write(fd, data_block_bitmap, 100 | sizeof(data_block_bitmap))) { 101 | ret = -4; 102 | break; 103 | } 104 | 105 | // write root inode 106 | if (sizeof(root_hellofs_inode) 107 | != write(fd, &root_hellofs_inode, 108 | sizeof(root_hellofs_inode))) { 109 | ret = -5; 110 | break; 111 | } 112 | 113 | // write welcome file inode 114 | if (sizeof(welcome_hellofs_inode) 115 | != write(fd, &welcome_hellofs_inode, 116 | sizeof(welcome_hellofs_inode))) { 117 | ret = -6; 118 | break; 119 | } 120 | 121 | // write root inode data block 122 | if ((off_t)-1 123 | == lseek( 124 | fd, 125 | HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB(&hellofs_sb) 126 | * hellofs_sb.blocksize, 127 | SEEK_SET)) { 128 | ret = -7; 129 | break; 130 | } 131 | if (sizeof(root_dir_records) 132 | != write(fd, root_dir_records, 133 | sizeof(root_dir_records))) { 134 | ret = -8; 135 | break; 136 | } 137 | 138 | // write welcome file inode data block 139 | if ((off_t)-1 140 | == lseek( 141 | fd, 142 | (HELLOFS_DATA_BLOCK_TABLE_START_BLOCK_NO_HSB(&hellofs_sb) 143 | + 1) * hellofs_sb.blocksize, 144 | SEEK_SET)) { 145 | ret = -9; 146 | break; 147 | } 148 | if (sizeof(welcome_body) != write(fd, welcome_body, 149 | sizeof(welcome_body))) { 150 | ret = -10; 151 | break; 152 | } 153 | } while (0); 154 | 155 | close(fd); 156 | return ret; 157 | } 158 | -------------------------------------------------------------------------------- /super.c: -------------------------------------------------------------------------------- 1 | #include "khellofs.h" 2 | 3 | static int hellofs_fill_super(struct super_block *sb, void *data, int silent) { 4 | struct inode *root_inode; 5 | struct hellofs_inode *root_hellofs_inode; 6 | struct buffer_head *bh; 7 | struct hellofs_superblock *hellofs_sb; 8 | int ret = 0; 9 | 10 | bh = sb_bread(sb, HELLOFS_SUPERBLOCK_BLOCK_NO); 11 | BUG_ON(!bh); 12 | hellofs_sb = (struct hellofs_superblock *)bh->b_data; 13 | if (unlikely(hellofs_sb->magic != HELLOFS_MAGIC)) { 14 | printk(KERN_ERR 15 | "The filesystem being mounted is not of type hellofs. " 16 | "Magic number mismatch: %llu != %llu\n", 17 | hellofs_sb->magic, (uint64_t)HELLOFS_MAGIC); 18 | goto release; 19 | } 20 | if (unlikely(sb->s_blocksize != hellofs_sb->blocksize)) { 21 | printk(KERN_ERR 22 | "hellofs seem to be formatted with mismatching blocksize: %lu\n", 23 | sb->s_blocksize); 24 | goto release; 25 | } 26 | 27 | sb->s_magic = hellofs_sb->magic; 28 | sb->s_fs_info = hellofs_sb; 29 | sb->s_maxbytes = hellofs_sb->blocksize; 30 | sb->s_op = &hellofs_sb_ops; 31 | 32 | root_hellofs_inode = hellofs_get_hellofs_inode(sb, HELLOFS_ROOTDIR_INODE_NO); 33 | root_inode = new_inode(sb); 34 | if (!root_inode || !root_hellofs_inode) { 35 | ret = -ENOMEM; 36 | goto release; 37 | } 38 | hellofs_fill_inode(sb, root_inode, root_hellofs_inode); 39 | inode_init_owner(root_inode, NULL, root_inode->i_mode); 40 | 41 | sb->s_root = d_make_root(root_inode); 42 | if (!sb->s_root) { 43 | ret = -ENOMEM; 44 | goto release; 45 | } 46 | 47 | release: 48 | brelse(bh); 49 | return ret; 50 | } 51 | 52 | struct dentry *hellofs_mount(struct file_system_type *fs_type, 53 | int flags, const char *dev_name, 54 | void *data) { 55 | struct dentry *ret; 56 | ret = mount_bdev(fs_type, flags, dev_name, data, hellofs_fill_super); 57 | 58 | if (unlikely(IS_ERR(ret))) { 59 | printk(KERN_ERR "Error mounting hellofs.\n"); 60 | } else { 61 | printk(KERN_INFO "hellofs is succesfully mounted on: %s\n", 62 | dev_name); 63 | } 64 | 65 | return ret; 66 | } 67 | 68 | void hellofs_kill_superblock(struct super_block *sb) { 69 | printk(KERN_INFO 70 | "hellofs superblock is destroyed. Unmount succesful.\n"); 71 | kill_block_super(sb); 72 | } 73 | 74 | void hellofs_put_super(struct super_block *sb) { 75 | return; 76 | } 77 | 78 | void hellofs_save_sb(struct super_block *sb) { 79 | struct buffer_head *bh; 80 | struct hellofs_superblock *hellofs_sb = HELLOFS_SB(sb); 81 | 82 | bh = sb_bread(sb, HELLOFS_SUPERBLOCK_BLOCK_NO); 83 | BUG_ON(!bh); 84 | 85 | bh->b_data = (char *)hellofs_sb; 86 | mark_buffer_dirty(bh); 87 | sync_dirty_buffer(bh); 88 | brelse(bh); 89 | } --------------------------------------------------------------------------------