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1e5773e0ba
The function btrfs_punch_hole_lock_range() needs to make sure there is
no other folio in the range, thus it goes with filemap_range_has_page(),
which works pretty fine.
But if we have large folios, under the following case
filemap_range_has_page() will always return true, forcing
btrfs_punch_hole_lock_range() to do a very time consuming busy loop:
start end
| |
|//|//|//|//| | | | | | | | |//|//|
\ / \ /
Folio A Folio B
In the above case, folio A and B contain our start/end indexes, and there
are no other folios in the range. Thus we do not need to retry inside
btrfs_punch_hole_lock_range().
To prepare for large data folios, introduce a helper,
check_range_has_page(), which will:
- Shrink the search range towards page boundaries
If the rounded down end (exclusive, otherwise it can underflow when @end
is inside the folio at file offset 0) is no larger than the rounded up
start, it means the range contains no other pages other than the ones
covering @start and @end.
Can return false directly in that case.
- Grab all the folios inside the range
- Skip any large folios that cover the start and end indexes
- If any other folios are found return true
- Otherwise return false
This new helper is going to handle both large folios and regular ones.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.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 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.