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xfs: debug mode forced buffered write failure

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Add a DEBUG mode-only sysfs knob to enable forced buffered write
failure. An additional side effect of this mode is brute force killing
of delayed allocation blocks in the range of the write. The latter is
the prime motiviation behind this patch, as userspace test
infrastructure requires a reliable mechanism to create and split
delalloc extents without causing extent conversion.

Certain fallocate operations (i.e., zero range) were used for this in
the past, but the implementations have changed such that delalloc
extents are flushed and converted to real blocks, rendering the test
useless.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Brian Foster
2016-03-15 11:42:44 +11:00
committed by Dave Chinner
parent 36f90b0a2d
commit 801cc4e17a
3 changed files with 101 additions and 11 deletions
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9
fs/xfs/xfs_aops.c
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@@ -1752,6 +1752,7 @@ xfs_vm_write_failed(
loff_t from = pos & (PAGE_CACHE_SIZE - 1);
loff_t to = from + len;
struct buffer_head *bh, *head;
struct xfs_mount *mp = XFS_I(inode)->i_mount;
/*
* The request pos offset might be 32 or 64 bit, this is all fine
@@ -1786,7 +1787,8 @@ xfs_vm_write_failed(
if (!buffer_delay(bh))
continue;
if (!buffer_new(bh) && block_offset < i_size_read(inode))
if (!xfs_mp_fail_writes(mp) && !buffer_new(bh) &&
block_offset < i_size_read(inode))
continue;
xfs_vm_kill_delalloc_range(inode, block_offset,
@@ -1824,6 +1826,7 @@ xfs_vm_write_begin(
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
struct page *page;
int status;
struct xfs_mount *mp = XFS_I(mapping->host)->i_mount;
ASSERT(len <= PAGE_CACHE_SIZE);
@@ -1832,6 +1835,8 @@ xfs_vm_write_begin(
return -ENOMEM;
status = __block_write_begin(page, pos, len, xfs_get_blocks);
if (xfs_mp_fail_writes(mp))
status = -EIO;
if (unlikely(status)) {
struct inode *inode = mapping->host;
size_t isize = i_size_read(inode);
@@ -1844,6 +1849,8 @@ xfs_vm_write_begin(
* allocated in this write, not blocks that were previously
* written successfully.
*/
if (xfs_mp_fail_writes(mp))
isize = 0;
if (pos + len > isize) {
ssize_t start = max_t(ssize_t, pos, isize);