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Ojaswin Mujoo
46c22a8bb4
Currently, our handling of metadata is _ambiguous_ in some scenarios,
that is, we end up returning unknown if the range only covers the
mapping partially.
For example, in the following case:
$ xfs_io -c fsmap -d
0: 254:16 [0..7]: static fs metadata 8
1: 254:16 [8..15]: special 102:1 8
2: 254:16 [16..5127]: special 102:2 5112
3: 254:16 [5128..5255]: special 102:3 128
4: 254:16 [5256..5383]: special 102:4 128
5: 254:16 [5384..70919]: inodes 65536
6: 254:16 [70920..70967]: unknown 48
...
$ xfs_io -c fsmap -d 24 33
0: 254:16 [24..39]: unknown 16 <--- incomplete reporting
$ xfs_io -c fsmap -d 24 33 (With patch)
0: 254:16 [16..5127]: special 102:2 5112
This is because earlier in ext4_getfsmap_meta_helper, we end up ignoring
any extent that starts before our queried range, but overlaps it. While
the man page [1] is a bit ambiguous on this, this fix makes the output
make more sense since we are anyways returning an "unknown" extent. This
is also consistent to how XFS does it:
$ xfs_io -c fsmap -d
...
6: 254:16 [104..127]: free space 24
7: 254:16 [128..191]: inodes 64
...
$ xfs_io -c fsmap -d 137 150
0: 254:16 [128..191]: inodes 64 <-- full extent returned
[1] https://man7.org/linux/man-pages/man2/ioctl_getfsmap.2.html
Reported-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Message-ID: <023f37e35ee280cd9baac0296cbadcbe10995cab.1757058211.git.ojaswin@linux.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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.