From 3ed3a4343b79a79d10e31f85f2d1afabcead76c6 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 5 Mar 2010 02:00:42 +0000 Subject: [PATCH] xfs: truncate delalloc extents when IO fails in writeback 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 Reviewed-by: Christoph Hellwig Signed-off-by: Alex Elder --- fs/xfs/linux-2.6/xfs_aops.c | 124 ++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 114 insertions(+), 10 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c index 793908a..9083357 100644 --- a/fs/xfs/linux-2.6/xfs_aops.c +++ b/fs/xfs/linux-2.6/xfs_aops.c @@ -39,6 +39,7 @@ #include "xfs_iomap.h" #include "xfs_vnodeops.h" #include "xfs_trace.h" +#include "xfs_bmap.h" #include #include #include @@ -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, -- 1.8.2.3