mainlining shenanigans
d62113303d
On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.
This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.
In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.
The following script reliably recreates the bug described above.
#!/usr/bin/bash
device=/dev/loop0
shortdev=$(basename $device)
mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating
errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent
umount $device > /dev/null 2>&1
echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi
echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi
echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1
sync
echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null
echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1
echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile
echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag
echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1
sync
echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1
This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.
Fixes:
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||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 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.