From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: mm/filemap: fix mapping_seek_hole_data on THP & 32-bit No problem on 64-bit without huge pages, but xfstests generic/285 and other SEEK_HOLE/SEEK_DATA tests have regressed on huge tmpfs, and on 32-bit architectures, with the new mapping_seek_hole_data(). Several different bugs turned out to need fixing. u64 cast to stop losing bits when converting unsigned long to loff_t (and let's use shifts throughout, rather than mixed with * and /). Use round_up() when advancing pos, to stop assuming that pos was already THP-aligned when advancing it by THP-size. (This use of round_up() assumes that any THP has THP-aligned index: true at present and true going forward, but could be recoded to avoid the assumption.) Use xas_set() when iterating away from a THP, so that xa_index stays in synch with start, instead of drifting away to return bogus offset. Check start against end to avoid wrapping 32-bit xa_index to 0 (and to handle these additional cases, seek_data or not, it's easier to break the loop than goto: so rearrange exit from the function). [hughd@xxxxxxxxxx: remove unneeded u64 casts, per Matthew] Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2104221347240.1170@eggly.anvils Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2104211737410.3299@eggly.anvils Fixes: 41139aa4c3a3 ("mm/filemap: add mapping_seek_hole_data") Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Dave Chinner <dchinner@xxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) --- a/mm/filemap.c~mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit +++ a/mm/filemap.c @@ -2678,7 +2678,7 @@ loff_t mapping_seek_hole_data(struct add loff_t end, int whence) { XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); - pgoff_t max = (end - 1) / PAGE_SIZE; + pgoff_t max = (end - 1) >> PAGE_SHIFT; bool seek_data = (whence == SEEK_DATA); struct page *page; @@ -2687,7 +2687,8 @@ loff_t mapping_seek_hole_data(struct add rcu_read_lock(); while ((page = find_get_entry(&xas, max, XA_PRESENT))) { - loff_t pos = xas.xa_index * PAGE_SIZE; + loff_t pos = (u64)xas.xa_index << PAGE_SHIFT; + unsigned int seek_size; if (start < pos) { if (!seek_data) @@ -2695,25 +2696,25 @@ loff_t mapping_seek_hole_data(struct add start = pos; } - pos += seek_page_size(&xas, page); + seek_size = seek_page_size(&xas, page); + pos = round_up(pos + 1, seek_size); start = page_seek_hole_data(&xas, mapping, page, start, pos, seek_data); if (start < pos) goto unlock; + if (start >= end) + break; + if (seek_size > PAGE_SIZE) + xas_set(&xas, pos >> PAGE_SHIFT); if (!xa_is_value(page)) put_page(page); } - rcu_read_unlock(); - if (seek_data) - return -ENXIO; - goto out; - + start = -ENXIO; unlock: rcu_read_unlock(); - if (!xa_is_value(page)) + if (page && !xa_is_value(page)) put_page(page); -out: if (start > end) return end; return start; _
