The patch titled
Subject: mm/filemap: fix mapping_seek_hole_data on THP & 32-bit
has been added to the -mm tree. Its filename is
mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch
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------------------------------------------------------
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 casts added to stop unfortunate sign-extension when shifting (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. (But I believe this use of
round_up() assumes that any THP must be THP-aligned: true while tmpfs
enforces that alignment, and is the only fs with FS_THP_SUPPORT; but might
need to be generalized in the future? If I try to generalize it right
now, I'm sure to get it wrong!)
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).
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 | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
--- a/mm/filemap.c~mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit
+++ a/mm/filemap.c
@@ -2677,8 +2677,8 @@ unsigned int seek_page_size(struct xa_st
loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
loff_t end, int whence)
{
- XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
- pgoff_t max = (end - 1) / PAGE_SIZE;
+ XA_STATE(xas, &mapping->i_pages, (u64)start >> PAGE_SHIFT);
+ pgoff_t max = (u64)(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((u64)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, (u64)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;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch
mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch
mm-restore-node-stat-checking-in-proc-sys-vm-stat_refresh.patch
mm-no-more-einval-from-proc-sys-vm-stat_refresh.patch
mm-proc-sys-vm-stat_refresh-skip-checking-known-negative-stats.patch
mm-proc-sys-vm-stat_refresh-stop-checking-monotonic-numa-stats.patch
