From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
William Kucharski <william.kucharski@oracle.com>,
Christoph Hellwig <hch@lst.de>, Jan Kara <jack@suse.cz>,
Dave Chinner <dchinner@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: [PATCH 2/2] mm/filemap: fix mapping_seek_hole_data on THP & 32-bit
Date: Wed, 21 Apr 2021 17:39:14 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.2104211737410.3299@eggly.anvils> (raw)
In-Reply-To: <alpine.LSU.2.11.2104211723580.3299@eggly.anvils>
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).
Fixes: 41139aa4c3a3 ("mm/filemap: add mapping_seek_hole_data")
Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/filemap.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
--- 5.12-rc8/mm/filemap.c 2021-02-26 19:42:39.812156085 -0800
+++ linux/mm/filemap.c 2021-04-20 23:20:20.509464440 -0700
@@ -2671,8 +2671,8 @@ 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;
@@ -2681,7 +2681,8 @@ 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)
@@ -2689,25 +2690,25 @@ 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;
next prev parent reply other threads:[~2021-04-22 0:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 0:35 [PATCH 0/2] mm/filemap: fix 5.12-rc regressions Hugh Dickins
2021-04-22 0:37 ` [PATCH 1/2] mm/filemap: fix find_lock_entries hang on 32-bit THP Hugh Dickins
2021-04-22 1:06 ` Matthew Wilcox
2021-04-22 0:39 ` Hugh Dickins [this message]
2021-04-22 1:16 ` [PATCH 2/2] mm/filemap: fix mapping_seek_hole_data on THP & 32-bit Matthew Wilcox
2021-04-22 5:55 ` Hugh Dickins
2021-04-22 20:46 ` Hugh Dickins
2021-04-22 20:48 ` [PATCH v2 " Hugh Dickins
2021-04-22 23:04 ` Andrew Morton
2021-04-23 17:22 ` Hugh Dickins
2021-04-23 19:29 ` Andrew Morton
2021-04-23 20:08 ` Hugh Dickins
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