| Message ID | b93aac5fb44b46cd5391f3d5d177c0976e7d5ce0.1725001507.git.wqu@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] btrfs: subpage: fix the bitmap dump which can cause bitmap corruption | expand |
On Fri, Aug 30, 2024 at 04:35:48PM +0930, Qu Wenruo wrote: > In commit 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for > debug") an internal macro GET_SUBPAGE_BITMAP() is introduced to grab the > bitmap of each attribute. > > But that commit is using bitmap_cut() which will do the left shift of > the larger bitmap, causing incorrect values. > > Thankfully this bitmap_cut() is only called for debug usage, and so far > it's not yet causing problem. > > Fix it to use bitmap_read() to only grab the desired sub-bitmap. > > Fixes: 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug") > Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> > --- > Changelog: > v2: > - Do not change the parameters of GET_SUBPAGE_BITMAP() > To minimal the backport needed. > --- > fs/btrfs/subpage.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c > index 663f2f953a65..ca7d2aedfa8d 100644 > --- a/fs/btrfs/subpage.c > +++ b/fs/btrfs/subpage.c > @@ -870,9 +870,14 @@ void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct fol > } > > #define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst) \ > - bitmap_cut(dst, subpage->bitmaps, 0, \ > - fs_info->sectors_per_page * btrfs_bitmap_nr_##name, \ > - fs_info->sectors_per_page) > +{ \ > + const int sectors_per_page = fs_info->sectors_per_page; \ > + \ > + ASSERT(sectors_per_page < BITS_PER_LONG); \ > + *dst = bitmap_read(subpage->bitmaps, \ Eventually this can be "dst = ...", the pointer was required for bitmap_cut, but like that it's also acceptable.
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 663f2f953a65..ca7d2aedfa8d 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -870,9 +870,14 @@ void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct fol } #define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst) \ - bitmap_cut(dst, subpage->bitmaps, 0, \ - fs_info->sectors_per_page * btrfs_bitmap_nr_##name, \ - fs_info->sectors_per_page) +{ \ + const int sectors_per_page = fs_info->sectors_per_page; \ + \ + ASSERT(sectors_per_page < BITS_PER_LONG); \ + *dst = bitmap_read(subpage->bitmaps, \ + sectors_per_page * btrfs_bitmap_nr_##name, \ + sectors_per_page); \ +} void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len)
In commit 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug") an internal macro GET_SUBPAGE_BITMAP() is introduced to grab the bitmap of each attribute. But that commit is using bitmap_cut() which will do the left shift of the larger bitmap, causing incorrect values. Thankfully this bitmap_cut() is only called for debug usage, and so far it's not yet causing problem. Fix it to use bitmap_read() to only grab the desired sub-bitmap. Fixes: 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug") Signed-off-by: Qu Wenruo <wqu@suse.com> --- Changelog: v2: - Do not change the parameters of GET_SUBPAGE_BITMAP() To minimal the backport needed. --- fs/btrfs/subpage.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)