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a3a0819388
copy_file_range tries to use the OSD 'copy-from' operation, which simply
performs a full object copy. Unfortunately, the implementation of this
system call assumes that stripe_count is always set to 1 and doesn't take
into account that the data may be striped across an object set. If the
file layout has stripe_count different from 1, then the destination file
data will be corrupted.
For example:
Consider a 8 MiB file with 4 MiB object size, stripe_count of 2 and
stripe_size of 2 MiB; the first half of the file will be filled with 'A's
and the second half will be filled with 'B's:
0 4M 8M Obj1 Obj2
+------+------+ +----+ +----+
file: | AAAA | BBBB | | AA | | AA |
+------+------+ |----| |----|
| BB | | BB |
+----+ +----+
If we copy_file_range this file into a new file (which needs to have the
same file layout!), then it will start by copying the object starting at
file offset 0 (Obj1). And then it will copy the object starting at file
offset 4M -- which is Obj1 again.
Unfortunately, the solution for this is to not allow remote object copies
to be performed when the file layout stripe_count is not 1 and simply
fallback to the default (VFS) copy_file_range implementation.
Cc: stable@vger.kernel.org
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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 Restructured Text 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.