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Ojaswin Mujoo bae76c035b ext4: fix fsmap end of range reporting with bigalloc 
With bigalloc enabled, the logic to report last extent has a bug since
we try to use cluster units instead of block units. This can cause an
issue where extra incorrect entries might be returned back to the
user. This was flagged by generic/365 with 64k bs and -O bigalloc.

** Details of issue **

The issue was noticed on 5G 64k blocksize FS with -O bigalloc which has
only 1 bg.

$ xfs_io -c "fsmap -d" /mnt/scratch

  0: 253:48 [0..127]: static fs metadata 128   /* sb */
  1: 253:48 [128..255]: special 102:1 128   /* gdt */
  3: 253:48 [256..383]: special 102:3 128   /* block bitmap */
  4: 253:48 [384..2303]: unknown 1920       /* flex bg empty space */
  5: 253:48 [2304..2431]: special 102:4 128   /* inode bitmap */
  6: 253:48 [2432..4351]: unknown 1920      /* flex bg empty space */
  7: 253:48 [4352..6911]: inodes 2560
  8: 253:48 [6912..538623]: unknown 531712
  9: 253:48 [538624..10485759]: free space 9947136

The issue can be seen with:

$ xfs_io -c "fsmap -d 0 3" /mnt/scratch

  0: 253:48 [0..127]: static fs metadata 128
  1: 253:48 [384..2047]: unknown 1664

Only the first entry was expected to be returned but we get 2. This is
because:

ext4_getfsmap_datadev()
  first_cluster, last_cluster = 0
  ...
  info->gfi_last = true;
  ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster + 1, 0, info);
    fsb = C2B(1) = 16
    fslen = 0
    ...
    /* Merge in any relevant extents from the meta_list */
    list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
      ...
      // since fsb = 16, considers all metadata which starts before 16 blockno
      iter 1: error = ext4_getfsmap_helper(sb, info, p);  // p = sb (0,1), nop
        info->gfi_next_fsblk = 1
      iter 2: error = ext4_getfsmap_helper(sb, info, p);  // p = gdt (1,2), nop
        info->gfi_next_fsblk = 2
      iter 3: error = ext4_getfsmap_helper(sb, info, p);  // p = blk bitmap (2,3), nop
        info->gfi_next_fsblk = 3
      iter 4: error = ext4_getfsmap_helper(sb, info, p);  // p = ino bitmap (18,19)
        if (rec_blk > info->gfi_next_fsblk) { // (18 > 3)
          // emits an extra entry ** BUG **
        }
    }

Fix this by directly calling ext4_getfsmap_datadev() with a dummy
record that has fmr_physical set to (end_fsb + 1) instead of
last_cluster + 1. By using the block instead of cluster we get the
correct behavior.

Replacing ext4_getfsmap_datadev_helper() with ext4_getfsmap_helper()
is okay since the gfi_lastfree and metadata checks in
ext4_getfsmap_datadev_helper() are anyways redundant when we only want
to emit the last allocated block of the range, as we have already
taken care of emitting metadata and any last free blocks.

Cc: stable@kernel.org
Reported-by: Disha Goel <disgoel@linux.ibm.com>
Fixes: 4a622e4d47 ("ext4: fix FS_IOC_GETFSMAP handling")
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/e7472c8535c9c5ec10f425f495366864ea12c9da.1754377641.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
 		2025-08-12 23:15:05 -04:00
Documentation TTY/Serial driver fixes for 6.16-rc4 2025-06-29 09:21:27 -07:00
LICENSES LICENSES: add CC0-1.0 license text 2025-05-21 14:54:17 +02:00
arch - Make sure DR6 and DR7 are initialized to their architectural values and not 2025-06-29 08:28:24 -07:00
block block-6.16-20250626 2025-06-27 09:02:33 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: wp512 - Use API partial block handling 2025-06-23 16:56:56 +08:00
drivers Staging driver fix for 6.16-rc4 2025-06-29 09:25:55 -07:00
fs ext4: fix fsmap end of range reporting with bigalloc 2025-08-12 23:15:05 -04:00
include ext4: get rid of some obsolete EXT4_MB_HINT flags 2025-07-25 09:14:16 -04:00
init init: fix build warnings about export.h 2025-06-11 22:42:36 -07:00
io_uring io_uring-6.16-20250626 2025-06-27 08:55:57 -07:00
ipc - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
kernel - Make sure an AUX perf event is really disabled when it overruns 2025-06-29 08:16:02 -07:00
lib 16 hotfixes. 6 are cc:stable and the remainder address post-6.15 issues 2025-06-27 20:34:10 -07:00
mm mm/damon/sysfs-schemes: free old damon_sysfs_scheme_filter->memcg_path on write 2025-06-25 15:55:03 -07:00
net Including fixes from bluetooth and wireless. 2025-06-26 09:13:27 -07:00
rust Driver core fixes for 6.16-rc3 2025-06-18 14:31:16 -07:00
samples - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
scripts scripts/gdb: fix dentry_name() lookup 2025-06-25 15:55:03 -07:00
security selinux: change security_compute_sid to return the ssid or tsid on match 2025-06-19 16:13:16 -04:00
sound ALSA: hda/realtek: Fix built-in mic on ASUS VivoBook X507UAR 2025-06-26 08:02:44 +02:00
tools LoongArch fixes for v6.16-rc4 2025-06-28 11:35:11 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge branch 'kvm-lockdep-common' into HEAD 2025-05-28 06:29:17 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore Python compiled bytecode 2025-04-24 10:12:46 -06:00
.mailmap 16 hotfixes. 6 are cc:stable and the remainder address post-6.15 issues 2025-06-27 20:34:10 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Add entry for Shannon Nelson 2025-06-21 07:34:28 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.16-rc4 2025-06-28 15:23:17 -07:00
Makefile Linux 6.16-rc4 2025-06-29 13:09:04 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.