1 files changed, 110 insertions, 62 deletions

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 09394ac2c180..dd0ce7b769ce 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -13,24 +13,6 @@
 #include <linux/pagevec.h>
 #include "internal.h"
 
-static void __netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
-{
-	if (netfs_group)
-		folio_attach_private(folio, netfs_get_group(netfs_group));
-}
-
-static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
-{
-	void *priv = folio_get_private(folio);
-
-	if (unlikely(priv != netfs_group)) {
-		if (netfs_group && (!priv || priv == NETFS_FOLIO_COPY_TO_CACHE))
-			folio_attach_private(folio, netfs_get_group(netfs_group));
-		else if (!netfs_group && priv == NETFS_FOLIO_COPY_TO_CACHE)
-			folio_detach_private(folio);
-	}
-}
-
 /*
  * Grab a folio for writing and lock it.  Attempt to allocate as large a folio
  * as possible to hold as much of the remaining length as possible in one go.
@@ -150,6 +132,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	}
 
 	do {
+		enum netfs_folio_trace trace;
 		struct netfs_folio *finfo;
 		struct netfs_group *group;
 		unsigned long long fpos;
@@ -157,6 +140,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		size_t offset;	/* Offset into pagecache folio */
 		size_t part;	/* Bytes to write to folio */
 		size_t copied;	/* Bytes copied from user */
+		void *priv;
 
 		offset = pos & (max_chunk - 1);
 		part = min(max_chunk - offset, iov_iter_count(iter));
@@ -202,29 +186,40 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			goto error_folio_unlock;
 		}
 
-		/* Decide how we should modify a folio.  We might be attempting
-		 * to do write-streaming, in which case we don't want to a
-		 * local RMW cycle if we can avoid it.  If we're doing local
-		 * caching or content crypto, we award that priority over
-		 * avoiding RMW.  If the file is open readably, then we also
-		 * assume that we may want to read what we wrote.
-		 */
 		finfo = netfs_folio_info(folio);
 		group = netfs_folio_group(folio);
 
+		/* If the requested group differs from the group set on the
+		 * page, then we need to flush out the folio if it has a group
+		 * set (ie. is non-NULL).  Note that COPY_TO_CACHE is a special
+		 * case, being a netfs annotation rather than an actual group.
+		 *
+		 * The filesystem isn't permitted to mix writes with groups and
+		 * writes without groups as the NULL group is used to indicate
+		 * that no group is set.
+		 */
 		if (unlikely(group != netfs_group) &&
-		    group != NETFS_FOLIO_COPY_TO_CACHE)
+		    group != NETFS_FOLIO_COPY_TO_CACHE &&
+		    group) {
+			WARN_ON_ONCE(!netfs_group);
 			goto flush_content;
+		}
 
+		/* Decide how we should modify a folio.  We might be attempting
+		 * to do write-streaming, as we don't want to a local RMW cycle
+		 * if we can avoid it.  If we're doing local caching or content
+		 * crypto, we award that priority over avoiding RMW.  If the
+		 * file is open readably, then we let ->read_folio() fill in
+		 * the gaps.
+		 */
 		if (folio_test_uptodate(folio)) {
 			if (mapping_writably_mapped(mapping))
 				flush_dcache_folio(folio);
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
 			if (unlikely(copied == 0))
 				goto copy_failed;
-			netfs_set_group(folio, netfs_group);
-			trace_netfs_folio(folio, netfs_folio_is_uptodate);
-			goto copied;
+			trace = netfs_folio_is_uptodate;
+			goto copied_uptodate;
 		}
 
 		/* If the page is above the zero-point then we assume that the
@@ -237,38 +232,53 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			folio_zero_segment(folio, offset + copied, flen);
-			__netfs_set_group(folio, netfs_group);
-			folio_mark_uptodate(folio);
-			trace_netfs_folio(folio, netfs_modify_and_clear);
-			goto copied;
+			if (finfo)
+				trace = netfs_modify_and_clear_rm_finfo;
+			else
+				trace = netfs_modify_and_clear;
+			goto mark_uptodate;
 		}
 
 		/* See if we can write a whole folio in one go. */
 		if (!maybe_trouble && offset == 0 && part >= flen) {
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
-			if (unlikely(copied == 0))
+			if (likely(copied == part)) {
+				if (finfo)
+					trace = netfs_whole_folio_modify_filled;
+				else
+					trace = netfs_whole_folio_modify;
+				goto mark_uptodate;
+			}
+			if (copied == 0)
 				goto copy_failed;
-			if (unlikely(copied < part)) {
+			if (!finfo || copied <= finfo->dirty_offset) {
 				maybe_trouble = true;
 				iov_iter_revert(iter, copied);
 				copied = 0;
 				folio_unlock(folio);
 				goto retry;
 			}
-			__netfs_set_group(folio, netfs_group);
-			folio_mark_uptodate(folio);
-			trace_netfs_folio(folio, netfs_whole_folio_modify);
+
+			/* We overwrote some existing dirty data, so we have to
+			 * accept the partial write.
+			 */
+			finfo->dirty_len += finfo->dirty_offset;
+			if (finfo->dirty_len == flen) {
+				trace = netfs_whole_folio_modify_filled_efault;
+				goto mark_uptodate;
+			}
+			if (copied > finfo->dirty_len)
+				finfo->dirty_len = copied;
+			finfo->dirty_offset = 0;
+			trace = netfs_whole_folio_modify_efault;
 			goto copied;
 		}
 
 		/* We don't want to do a streaming write on a file that loses
 		 * caching service temporarily because the backing store got
-		 * culled and we don't really want to get a streaming write on
-		 * a file that's open for reading as ->read_folio() then has to
-		 * be able to flush it.
+		 * culled.
 		 */
-		if ((file->f_mode & FMODE_READ) ||
-		    netfs_is_cache_enabled(ctx)) {
+		if (netfs_is_cache_enabled(ctx)) {
 			if (finfo) {
 				netfs_stat(&netfs_n_wh_wstream_conflict);
 				goto flush_content;
@@ -283,11 +293,11 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
 			if (unlikely(copied == 0))
 				goto copy_failed;
-			netfs_set_group(folio, netfs_group);
-			trace_netfs_folio(folio, netfs_just_prefetch);
-			goto copied;
+			trace = netfs_just_prefetch;
+			goto copied_uptodate;
 		}
 
+		/* Do a streaming write on a folio that has nothing in it yet. */
 		if (!finfo) {
 			ret = -EIO;
 			if (WARN_ON(folio_get_private(folio)))
@@ -296,10 +306,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			if (offset == 0 && copied == flen) {
-				__netfs_set_group(folio, netfs_group);
-				folio_mark_uptodate(folio);
-				trace_netfs_folio(folio, netfs_streaming_filled_page);
-				goto copied;
+				trace = netfs_streaming_filled_page;
+				goto mark_uptodate;
 			}
 
 			finfo = kzalloc(sizeof(*finfo), GFP_KERNEL);
@@ -313,7 +321,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			finfo->dirty_len = copied;
 			folio_attach_private(folio, (void *)((unsigned long)finfo |
 							     NETFS_FOLIO_INFO));
-			trace_netfs_folio(folio, netfs_streaming_write);
+			trace = netfs_streaming_write;
 			goto copied;
 		}
 
@@ -327,16 +335,10 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 				goto copy_failed;
 			finfo->dirty_len += copied;
 			if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
-				if (finfo->netfs_group)
-					folio_change_private(folio, finfo->netfs_group);
-				else
-					folio_detach_private(folio);
-				folio_mark_uptodate(folio);
-				kfree(finfo);
-				trace_netfs_folio(folio, netfs_streaming_cont_filled_page);
-			} else {
-				trace_netfs_folio(folio, netfs_streaming_write_cont);
+				trace = netfs_streaming_cont_filled_page;
+				goto mark_uptodate;
 			}
+			trace = netfs_streaming_write_cont;
 			goto copied;
 		}
 
@@ -350,7 +352,38 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			goto out;
 		continue;
 
+		/* Mark a folio as being up to data when we've filled it
+		 * completely.  If the folio has a group attached, then it must
+		 * be the same group, otherwise we should have flushed it out
+		 * above.  We have to get rid of the netfs_folio struct if
+		 * there was one.
+		 */
+	mark_uptodate:
+		folio_mark_uptodate(folio);
+
+	copied_uptodate:
+		priv = folio_get_private(folio);
+		if (likely(priv == netfs_group)) {
+			/* Already set correctly; no change required. */
+		} else if (priv == NETFS_FOLIO_COPY_TO_CACHE) {
+			if (!netfs_group)
+				folio_detach_private(folio);
+			else
+				folio_change_private(folio, netfs_get_group(netfs_group));
+		} else if (!priv) {
+			folio_attach_private(folio, netfs_get_group(netfs_group));
+		} else {
+			WARN_ON_ONCE(!finfo);
+			if (netfs_group)
+				/* finfo->netfs_group has a ref */
+				folio_change_private(folio, netfs_group);
+			else
+				folio_detach_private(folio);
+			kfree(finfo);
+		}
+
 	copied:
+		trace_netfs_folio(folio, trace);
 		flush_dcache_folio(folio);
 
 		/* Update the inode size if we moved the EOF marker */
@@ -511,6 +544,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 	struct inode *inode = file_inode(file);
 	struct netfs_inode *ictx = netfs_inode(inode);
 	vm_fault_t ret = VM_FAULT_NOPAGE;
+	void *priv;
 	int err;
 
 	_enter("%lx", folio->index);
@@ -531,7 +565,9 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 	}
 
 	group = netfs_folio_group(folio);
-	if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE) {
+	if (group &&
+	    group != netfs_group &&
+	    group != NETFS_FOLIO_COPY_TO_CACHE) {
 		folio_unlock(folio);
 		err = filemap_fdatawrite_range(mapping,
 					       folio_pos(folio),
@@ -553,7 +589,19 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 		trace_netfs_folio(folio, netfs_folio_trace_mkwrite_plus);
 	else
 		trace_netfs_folio(folio, netfs_folio_trace_mkwrite);
-	netfs_set_group(folio, netfs_group);
+
+	priv = folio_get_private(folio);
+	if (priv != netfs_group) {
+		if (!netfs_group && priv == NETFS_FOLIO_COPY_TO_CACHE)
+			folio_detach_private(folio);
+		else if (netfs_group && priv == NETFS_FOLIO_COPY_TO_CACHE)
+			folio_change_private(folio, netfs_get_group(netfs_group));
+		else if (netfs_group && !priv)
+			folio_attach_private(folio, netfs_get_group(netfs_group));
+		else
+			WARN_ON_ONCE(1);
+	}
+
 	file_update_time(file);
 	set_bit(NETFS_ICTX_MODIFIED_ATTR, &ictx->flags);
 	if (ictx->ops->post_modify)