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xfs: truncate delalloc extents when IO fails in writeback

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We currently use block_invalidatepage() to clean up pages where I/O
fails in ->writepage(). Unfortunately, if the page has delalloc
regions on it, we fail to remove the delalloc regions when we
invalidate the page.  This can result in tripping a BUG() in
xfs_get_blocks() later on if a direct IO read is done on that same
region - the delalloc extent is returned when none is supposed to be
there.

Fix this by truncating away the delalloc regions on the page before
invalidating it. Because they are delalloc, we can do this without
needing a transaction. Indeed - if we get ENOSPC errors, we have to
be able to do this truncation without a transaction as there is
no space left for block reservation (typically why we see a ENOSPC
in writeback).

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Dave Chinner 2010-03-05 02:00:42 +00:00 committed by Alex Elder
parent 20f6b2c785
commit 3ed3a4343b
1 changed files with 114 additions and 10 deletions
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124
fs/xfs/linux-2.6/xfs_aops.c
View File

@ -39,6 +39,7 @@
#include "xfs_iomap.h"
#include "xfs_vnodeops.h"
#include "xfs_trace.h"
#include "xfs_bmap.h"
#include <linux/mpage.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
@ -893,6 +894,118 @@ xfs_cluster_write(
}
}
STATIC void
xfs_vm_invalidatepage(
struct page *page,
unsigned long offset)
{
trace_xfs_invalidatepage(page->mapping->host, page, offset);
block_invalidatepage(page, offset);
}
/*
* If the page has delalloc buffers on it, we need to punch them out before we
* invalidate the page. If we don't, we leave a stale delalloc mapping on the
* inode that can trip a BUG() in xfs_get_blocks() later on if a direct IO read
* is done on that same region - the delalloc extent is returned when none is
* supposed to be there.
*
* We prevent this by truncating away the delalloc regions on the page before
* invalidating it. Because they are delalloc, we can do this without needing a
* transaction. Indeed - if we get ENOSPC errors, we have to be able to do this
* truncation without a transaction as there is no space left for block
* reservation (typically why we see a ENOSPC in writeback).
*
* This is not a performance critical path, so for now just do the punching a
* buffer head at a time.
*/
STATIC void
xfs_aops_discard_page(
struct page *page)
{
struct inode *inode = page->mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct buffer_head *bh, *head;
loff_t offset = page_offset(page);
ssize_t len = 1 << inode->i_blkbits;
if (!xfs_is_delayed_page(page, IOMAP_DELAY))
goto out_invalidate;
xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
"page discard on page %p, inode 0x%llx, offset %llu.",
page, ip->i_ino, offset);
xfs_ilock(ip, XFS_ILOCK_EXCL);
bh = head = page_buffers(page);
do {
int done;
xfs_fileoff_t offset_fsb;
xfs_bmbt_irec_t imap;
int nimaps = 1;
int error;
xfs_fsblock_t firstblock;
xfs_bmap_free_t flist;
if (!buffer_delay(bh))
goto next_buffer;
offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
/*
* Map the range first and check that it is a delalloc extent
* before trying to unmap the range. Otherwise we will be
* trying to remove a real extent (which requires a
* transaction) or a hole, which is probably a bad idea...
*/
error = xfs_bmapi(NULL, ip, offset_fsb, 1,
XFS_BMAPI_ENTIRE, NULL, 0, &imap,
&nimaps, NULL, NULL);
if (error) {
/* something screwed, just bail */
xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
"page discard failed delalloc mapping lookup.");
break;
}
if (!nimaps) {
/* nothing there */
goto next_buffer;
}
if (imap.br_startblock != DELAYSTARTBLOCK) {
/* been converted, ignore */
goto next_buffer;
}
WARN_ON(imap.br_blockcount == 0);
/*
* Note: while we initialise the firstblock/flist pair, they
* should never be used because blocks should never be
* allocated or freed for a delalloc extent and hence we need
* don't cancel or finish them after the xfs_bunmapi() call.
*/
xfs_bmap_init(&flist, &firstblock);
error = xfs_bunmapi(NULL, ip, offset_fsb, 1, 0, 1, &firstblock,
&flist, NULL, &done);
ASSERT(!flist.xbf_count && !flist.xbf_first);
if (error) {
/* something screwed, just bail */
xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
"page discard unable to remove delalloc mapping.");
break;
}
next_buffer:
offset += len;
} while ((bh = bh->b_this_page) != head);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
out_invalidate:
xfs_vm_invalidatepage(page, 0);
return;
}
/*
* Calling this without startio set means we are being asked to make a dirty
* page ready for freeing it's buffers. When called with startio set then
@ -1144,7 +1257,7 @@ error:
*/
if (err != -EAGAIN) {
if (!unmapped)
block_invalidatepage(page, 0);
xfs_aops_discard_page(page);
ClearPageUptodate(page);
}
return err;
@ -1554,15 +1667,6 @@ xfs_vm_readpages(
return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
}
STATIC void
xfs_vm_invalidatepage(
struct page *page,
unsigned long offset)
{
trace_xfs_invalidatepage(page->mapping->host, page, offset);
block_invalidatepage(page, offset);
}
const struct address_space_operations xfs_address_space_operations = {
.readpage = xfs_vm_readpage,
.readpages = xfs_vm_readpages,