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When we have the no-holes mode enabled and fsync a file after punching a
hole in it, we can end up not logging the whole hole range in the log tree.
This happens if the file has extent items that span more than one leaf and
we punch a hole that covers a range that starts in a leaf but does not go
beyond the offset of the first extent in the next leaf.
Example:
$ mkfs.btrfs -f -O no-holes -n 65536 /dev/sdb
$ mount /dev/sdb /mnt
$ for ((i = 0; i <= 831; i++)); do
offset=$((i * 2 * 256 * 1024))
xfs_io -f -c "pwrite -S 0xab -b 256K $offset 256K" \
/mnt/foobar >/dev/null
done
$ sync
# We now have 2 leafs in our filesystem fs tree, the first leaf has an
# item corresponding the extent at file offset 216530944 and the second
# leaf has a first item corresponding to the extent at offset 217055232.
# Now we punch a hole that partially covers the range of the extent at
# offset 216530944 but does go beyond the offset 217055232.
$ xfs_io -c "fpunch $((216530944 + 128 * 1024 - 4000)) 256K" /mnt/foobar
$ xfs_io -c "fsync" /mnt/foobar
<power fail>
# mount to replay the log
$ mount /dev/sdb /mnt
# Before this patch, only the subrange [216658016, 216662016[ (length of
# 4000 bytes) was logged, leaving an incorrect file layout after log
# replay.
Fix this by checking if there is a hole between the last extent item that
we processed and the first extent item in the next leaf, and if there is
one, log an explicit hole extent item.
Fixes:
|
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.