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Wong" Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Christoph Hellwig Subject: Re: [PATCH v4 02/10] iomap: split out iomap check and reset logic from iter advance Message-ID: References: <20250204133044.80551-1-bfoster@redhat.com> <20250204133044.80551-3-bfoster@redhat.com> <20250204193056.GD21808@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250204193056.GD21808@frogsfrogsfrogs> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On Tue, Feb 04, 2025 at 11:30:56AM -0800, Darrick J. Wong wrote: > On Tue, Feb 04, 2025 at 08:30:36AM -0500, Brian Foster wrote: > > In preparation for more granular iomap_iter advancing, break out > > some of the logic associated with higher level iteration from > > iomap_advance_iter(). Specifically, factor the iomap reset code into > > a separate helper and lift the iomap.length check into the calling > > code, similar to how ->iomap_end() calls are handled. > > > > Signed-off-by: Brian Foster > > Reviewed-by: Christoph Hellwig > > --- > > fs/iomap/iter.c | 49 ++++++++++++++++++++++++++----------------------- > > 1 file changed, 26 insertions(+), 23 deletions(-) > > > > diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c > > index 3790918646af..731ea7267f27 100644 > > --- a/fs/iomap/iter.c > > +++ b/fs/iomap/iter.c > > @@ -7,6 +7,13 @@ > > #include > > #include "trace.h" > > > > +static inline void iomap_iter_reset_iomap(struct iomap_iter *iter) > > +{ > > + iter->processed = 0; > > + memset(&iter->iomap, 0, sizeof(iter->iomap)); > > + memset(&iter->srcmap, 0, sizeof(iter->srcmap)); > > +} > > + > > /* > > * Advance to the next range we need to map. > > * > > @@ -14,32 +21,24 @@ > > * processed - it was aborted because the extent the iomap spanned may have been > > * changed during the operation. In this case, the iteration behaviour is to > > * remap the unprocessed range of the iter, and that means we may need to remap > > - * even when we've made no progress (i.e. iter->processed = 0). Hence the > > - * "finished iterating" case needs to distinguish between > > - * (processed = 0) meaning we are done and (processed = 0 && stale) meaning we > > - * need to remap the entire remaining range. > > + * even when we've made no progress (i.e. count = 0). Hence the "finished > > + * iterating" case needs to distinguish between (count = 0) meaning we are done > > + * and (count = 0 && stale) meaning we need to remap the entire remaining range. > > */ > > -static inline int iomap_iter_advance(struct iomap_iter *iter) > > +static inline int iomap_iter_advance(struct iomap_iter *iter, s64 count) > > { > > bool stale = iter->iomap.flags & IOMAP_F_STALE; > > int ret = 1; > > > > - /* handle the previous iteration (if any) */ > > - if (iter->iomap.length) { > > - if (iter->processed < 0) > > - return iter->processed; > > - if (WARN_ON_ONCE(iter->processed > iomap_length(iter))) > > - return -EIO; > > - iter->pos += iter->processed; > > - iter->len -= iter->processed; > > - if (!iter->len || (!iter->processed && !stale)) > > - ret = 0; > > - } > > + if (count < 0) > > + return count; > > + if (WARN_ON_ONCE(count > iomap_length(iter))) > > + return -EIO; > > + iter->pos += count; > > + iter->len -= count; > > + if (!iter->len || (!count && !stale)) > > + ret = 0; > > > > - /* clear the per iteration state */ > > - iter->processed = 0; > > - memset(&iter->iomap, 0, sizeof(iter->iomap)); > > - memset(&iter->srcmap, 0, sizeof(iter->srcmap)); > > Are there any consequences to not resetting the iter if > iter->iomap.length is zero? I think the answer is "no" because callers > are supposed to initialize the iter with zeroes and filesystems are > never supposed to return zero-length iomaps from ->begin_iomap, right? > That matches my understanding.. > If the answers are "no" and "yes" then > Reviewed-by: "Darrick J. Wong" > Thanks. Brian > --D > > > return ret; > > } > > > > @@ -82,10 +81,14 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops) > > return ret; > > } > > > > + /* advance and clear state from the previous iteration */ > > trace_iomap_iter(iter, ops, _RET_IP_); > > - ret = iomap_iter_advance(iter); > > - if (ret <= 0) > > - return ret; > > + if (iter->iomap.length) { > > + ret = iomap_iter_advance(iter, iter->processed); > > + iomap_iter_reset_iomap(iter); > > + if (ret <= 0) > > + return ret; > > + } > > > > ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags, > > &iter->iomap, &iter->srcmap); > > -- > > 2.48.1 > > > > >