| Message ID | d4a055317bdb8ecbd7e6d9bdb5ebb074fa93f7f8.1710769876.git.tavianator@tavianator.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | extent_buffer read cleanups | expand |
在 2024/3/19 00:26, Tavian Barnes 写道: > We recently tracked down a race condition that triggered a read for an > extent buffer with EXTENT_BUFFER_UPTODATE already set. While this read > was in progress, other concurrent readers would see the UPTODATE bit and > return early as if the read was already complete, making accesses to the > extent buffer conflict with the read operation that was overwriting it. > > Add a WARN_ON() to end_bbio_meta_read() for this situation to make > similar races easier to spot in the future. > > Signed-off-by: Tavian Barnes <tavianator@tavianator.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Thanks, Qu > --- > fs/btrfs/extent_io.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index 46173dcfde4f..0024ea20bfc4 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -4285,6 +4285,13 @@ static void end_bbio_meta_read(struct btrfs_bio *bbio) > struct folio_iter fi; > u32 bio_offset = 0; > > + /* > + * If the extent buffer is marked UPTODATE before the read operation > + * completes, other calls to read_extent_buffer_pages() will return > + * early without waiting for the read to finish, causing data races. > + */ > + WARN_ON(test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)); > + > eb->read_mirror = bbio->mirror_num; > > if (uptodate &&
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 46173dcfde4f..0024ea20bfc4 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4285,6 +4285,13 @@ static void end_bbio_meta_read(struct btrfs_bio *bbio) struct folio_iter fi; u32 bio_offset = 0; + /* + * If the extent buffer is marked UPTODATE before the read operation + * completes, other calls to read_extent_buffer_pages() will return + * early without waiting for the read to finish, causing data races. + */ + WARN_ON(test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)); + eb->read_mirror = bbio->mirror_num; if (uptodate &&
We recently tracked down a race condition that triggered a read for an extent buffer with EXTENT_BUFFER_UPTODATE already set. While this read was in progress, other concurrent readers would see the UPTODATE bit and return early as if the read was already complete, making accesses to the extent buffer conflict with the read operation that was overwriting it. Add a WARN_ON() to end_bbio_meta_read() for this situation to make similar races easier to spot in the future. Signed-off-by: Tavian Barnes <tavianator@tavianator.com> --- fs/btrfs/extent_io.c | 7 +++++++ 1 file changed, 7 insertions(+)