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iomap: support partial page discard on writeback block mapping failure
iomap writeback mapping failure only calls into ->discard_page() if the current page has not been added to the ioend. Accordingly, the XFS callback assumes a full page discard and invalidation. This is problematic for sub-page block size filesystems where some portion of a page might have been mapped successfully before a failure to map a delalloc block occurs. ->discard_page() is not called in that error scenario and the bio is explicitly failed by iomap via the error return from ->prepare_ioend(). As a result, the filesystem leaks delalloc blocks and corrupts the filesystem block counters. Since XFS is the only user of ->discard_page(), tweak the semantics to invoke the callback unconditionally on mapping errors and provide the file offset that failed to map. Update xfs_discard_page() to discard the corresponding portion of the file and pass the range along to iomap_invalidatepage(). The latter already properly handles both full and sub-page scenarios by not changing any iomap or page state on sub-page invalidations. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
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@ -1382,14 +1382,15 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
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* appropriately.
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*/
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if (unlikely(error)) {
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/*
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* Let the filesystem know what portion of the current page
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* failed to map. If the page wasn't been added to ioend, it
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* won't be affected by I/O completion and we must unlock it
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* now.
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*/
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if (wpc->ops->discard_page)
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wpc->ops->discard_page(page, file_offset);
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if (!count) {
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/*
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* If the current page hasn't been added to ioend, it
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* won't be affected by I/O completions and we must
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* discard and unlock it right here.
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*/
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if (wpc->ops->discard_page)
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wpc->ops->discard_page(page);
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ClearPageUptodate(page);
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unlock_page(page);
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goto done;
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@ -527,13 +527,15 @@ xfs_prepare_ioend(
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*/
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static void
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xfs_discard_page(
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struct page *page)
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struct page *page,
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loff_t fileoff)
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{
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struct inode *inode = page->mapping->host;
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struct xfs_inode *ip = XFS_I(inode);
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struct xfs_mount *mp = ip->i_mount;
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loff_t offset = page_offset(page);
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xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, offset);
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unsigned int pageoff = offset_in_page(fileoff);
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xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, fileoff);
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xfs_fileoff_t pageoff_fsb = XFS_B_TO_FSBT(mp, pageoff);
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int error;
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if (XFS_FORCED_SHUTDOWN(mp))
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@ -541,14 +543,14 @@ xfs_discard_page(
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xfs_alert_ratelimited(mp,
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"page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
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page, ip->i_ino, offset);
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page, ip->i_ino, fileoff);
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error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
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i_blocks_per_page(inode, page));
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i_blocks_per_page(inode, page) - pageoff_fsb);
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if (error && !XFS_FORCED_SHUTDOWN(mp))
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xfs_alert(mp, "page discard unable to remove delalloc mapping.");
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out_invalidate:
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iomap_invalidatepage(page, 0, PAGE_SIZE);
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iomap_invalidatepage(page, pageoff, PAGE_SIZE - pageoff);
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}
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static const struct iomap_writeback_ops xfs_writeback_ops = {
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@ -221,7 +221,7 @@ struct iomap_writeback_ops {
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* Optional, allows the file system to discard state on a page where
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* we failed to submit any I/O.
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*/
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void (*discard_page)(struct page *page);
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void (*discard_page)(struct page *page, loff_t fileoff);
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};
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struct iomap_writepage_ctx {
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