31 files changed, 241 insertions, 89 deletions

diff --git a/Documentation/errseq.rst b/Documentation/errseq.rst
new file mode 100644
index 0000000..4c29bd5
--- /dev/null
+++ b/Documentation/errseq.rst
@@ -0,0 +1,149 @@
+The errseq_t datatype
+=====================
+An errseq_t is a way of recording errors in one place, and allowing any
+number of "subscribers" to tell whether it has changed since a previous
+point where it was sampled.
+
+The initial use case for this is tracking errors for file
+synchronization syscalls (fsync, fdatasync, msync and sync_file_range),
+but it may be usable in other situations.
+
+It's implemented as an unsigned 32-bit value.  The low order bits are
+designated to hold an error code (between 1 and MAX_ERRNO).  The upper bits
+are used as a counter.  This is done with atomics instead of locking so that
+these functions can be called from any context.
+
+Note that there is a risk of collisions if new errors are being recorded
+frequently, since we have so few bits to use as a counter.
+
+To mitigate this, the bit between the error value and counter is used as
+a flag to tell whether the value has been sampled since a new value was
+recorded.  That allows us to avoid bumping the counter if no one has
+sampled it since the last time an error was recorded.
+
+Thus we end up with a value that looks something like this::
+
+    bit:  31..13        12        11..0
+    +-----------------+----+----------------+
+    |     counter     | SF |      errno     |
+    +-----------------+----+----------------+
+
+The general idea is for "watchers" to sample an errseq_t value and keep
+it as a running cursor.  That value can later be used to tell whether
+any new errors have occurred since that sampling was done, and atomically
+record the state at the time that it was checked.  This allows us to
+record errors in one place, and then have a number of "watchers" that
+can tell whether the value has changed since they last checked it.
+
+A new errseq_t should always be zeroed out.  An errseq_t value of all zeroes
+is the special (but common) case where there has never been an error. An all
+zero value thus serves as the "epoch" if one wishes to know whether there
+has ever been an error set since it was first initialized.
+
+API usage
+=========
+Let me tell you a story about a worker drone.  Now, he's a good worker
+overall, but the company is a little...management heavy.  He has to
+report to 77 supervisors today, and tomorrow the "big boss" is coming in
+from out of town and he's sure to test the poor fellow too.
+
+They're all handing him work to do -- so much he can't keep track of who
+handed him what, but that's not really a big problem.  The supervisors
+just want to know when he's finished all of the work they've handed him so
+far and whether he made any mistakes since they last asked.
+
+He might have made the mistake on work they didn't actually hand him,
+but he can't keep track of things at that level of detail, all he can
+remember is the most recent mistake that he made.
+
+Here's our worker_drone representation::
+
+        struct worker_drone {
+                errseq_t        wd_err; /* for recording errors */
+        };
+
+Every day, the worker_drone starts out with a blank slate::
+
+        struct worker_drone wd;
+
+        wd.wd_err = (errseq_t)0;
+
+The supervisors come in and get an initial read for the day.  They
+don't care about anything that happened before their watch begins::
+
+        struct supervisor {
+                errseq_t        s_wd_err; /* private "cursor" for wd_err */
+                spinlock_t      s_wd_err_lock; /* protects s_wd_err */
+        }
+
+        struct supervisor       su;
+
+        su.s_wd_err = errseq_sample(&wd.wd_err);
+        spin_lock_init(&su.s_wd_err_lock);
+
+Now they start handing him tasks to do.  Every few minutes they ask him to
+finish up all of the work they've handed him so far.  Then they ask him
+whether he made any mistakes on any of it::
+
+        spin_lock(&su.su_wd_err_lock);
+        err = errseq_check_and_advance(&wd.wd_err, &su.s_wd_err);
+        spin_unlock(&su.su_wd_err_lock);
+
+Up to this point, that just keeps returning 0.
+
+Now, the owners of this company are quite miserly and have given him
+substandard equipment with which to do his job. Occasionally it
+glitches and he makes a mistake.  He sighs a heavy sigh, and marks it
+down::
+
+        errseq_set(&wd.wd_err, -EIO);
+
+...and then gets back to work.  The supervisors eventually poll again
+and they each get the error when they next check.  Subsequent calls will
+return 0, until another error is recorded, at which point it's reported
+to each of them once.
+
+Note that the supervisors can't tell how many mistakes he made, only
+whether one was made since they last checked, and the latest value
+recorded.
+
+Occasionally the big boss comes in for a spot check and asks the worker
+to do a one-off job for him. He's not really watching the worker
+full-time like the supervisors, but he does need to know whether a
+mistake occurred while his job was processing.
+
+He can just sample the current errseq_t in the worker, and then use that
+to tell whether an error has occurred later::
+
+        errseq_t since = errseq_sample(&wd.wd_err);
+        /* submit some work and wait for it to complete */
+        err = errseq_check(&wd.wd_err, since);
+
+Since he's just going to discard "since" after that point, he doesn't
+need to advance it here. He also doesn't need any locking since it's
+not usable by anyone else.
+
+Serializing errseq_t cursor updates
+===================================
+Note that the errseq_t API does not protect the errseq_t cursor during a
+check_and_advance_operation. Only the canonical error code is handled
+atomically.  In a situation where more than one task might be using the
+same errseq_t cursor at the same time, it's important to serialize
+updates to that cursor.
+
+If that's not done, then it's possible for the cursor to go backward
+in which case the same error could be reported more than once.
+
+Because of this, it's often advantageous to first do an errseq_check to
+see if anything has changed, and only later do an
+errseq_check_and_advance after taking the lock. e.g.::
+
+        if (errseq_check(&wd.wd_err, READ_ONCE(su.s_wd_err)) {
+                /* su.s_wd_err is protected by s_wd_err_lock */
+                spin_lock(&su.s_wd_err_lock);
+                err = errseq_check_and_advance(&wd.wd_err, &su.s_wd_err);
+                spin_unlock(&su.s_wd_err_lock);
+        }
+
+That avoids the spinlock in the common case where nothing has changed
+since the last time it was checked.
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index ae2f740..5ffcdeb 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -1749,7 +1749,7 @@ out:
 static int spufs_mfc_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct inode *inode = file_inode(file);
-	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	int err = file_write_and_wait_range(file, start, end);
 	if (!err) {
 		inode_lock(inode);
 		err = spufs_mfc_flush(file, NULL);
diff --git a/drivers/staging/lustre/lustre/llite/file.c b/drivers/staging/lustre/lustre/llite/file.c
index 2c30e42..be66545 100644
--- a/drivers/staging/lustre/lustre/llite/file.c
+++ b/drivers/staging/lustre/lustre/llite/file.c
@@ -2364,7 +2364,7 @@ int ll_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	       PFID(ll_inode2fid(inode)), inode);
 	ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_FSYNC, 1);
 
-	rc = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	rc = file_write_and_wait_range(file, start, end);
 	inode_lock(inode);
 
 	/* catch async errors that were recorded back when async writeback
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 37f69c0..487d5e3 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -69,7 +69,7 @@ int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasy
 {
 	struct fb_info *info = file->private_data;
 	struct inode *inode = file_inode(file);
-	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	int err = file_write_and_wait_range(file, start, end);
 	if (err)
 		return err;
 
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 43c242e..03c9e32 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -445,7 +445,7 @@ static int v9fs_file_fsync(struct file *filp, loff_t start, loff_t end,
 	struct p9_wstat wstat;
 	int retval;
 
-	retval = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	retval = file_write_and_wait_range(filp, start, end);
 	if (retval)
 		return retval;
 
@@ -468,7 +468,7 @@ int v9fs_file_fsync_dotl(struct file *filp, loff_t start, loff_t end,
 	struct inode *inode = filp->f_mapping->host;
 	int retval;
 
-	retval = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	retval = file_write_and_wait_range(filp, start, end);
 	if (retval)
 		return retval;
 
diff --git a/fs/affs/file.c b/fs/affs/file.c
index 196ee7f..0033181 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -954,7 +954,7 @@ int affs_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	struct inode *inode = filp->f_mapping->host;
 	int ret, err;
 
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 2d2fccd..106e43d 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -714,7 +714,7 @@ int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	       vnode->fid.vid, vnode->fid.vnode, file,
 	       datasync);
 
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(file, start, end);
 	if (ret)
 		return ret;
 	inode_lock(inode);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index bc09df6..0786f19 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2329,7 +2329,7 @@ int cifs_strict_fsync(struct file *file, loff_t start, loff_t end,
 	struct inode *inode = file_inode(file);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 
-	rc = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	rc = file_write_and_wait_range(file, start, end);
 	if (rc)
 		return rc;
 	inode_lock(inode);
@@ -2371,7 +2371,7 @@ int cifs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(file);
 	struct inode *inode = file->f_mapping->host;
 
-	rc = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	rc = file_write_and_wait_range(file, start, end);
 	if (rc)
 		return rc;
 	inode_lock(inode);
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index ca4e837..c74ed3c 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -328,7 +328,7 @@ ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	int rc;
 
-	rc = filemap_write_and_wait(file->f_mapping);
+	rc = file_write_and_wait(file);
 	if (rc)
 		return rc;
 
diff --git a/fs/exofs/file.c b/fs/exofs/file.c
index 28645f0..a94594e 100644
--- a/fs/exofs/file.c
+++ b/fs/exofs/file.c
@@ -48,7 +48,7 @@ static int exofs_file_fsync(struct file *filp, loff_t start, loff_t end,
 	struct inode *inode = filp->f_mapping->host;
 	int ret;
 
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(filp, start, end);
 	if (ret)
 		return ret;
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 2706130..843a0d9 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -206,7 +206,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
 	/* if fdatasync is triggered, let's do in-place-update */
 	if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
 		set_inode_flag(inode, FI_NEED_IPU);
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(file, start, end);
 	clear_inode_flag(inode, FI_NEED_IPU);
 
 	if (ret) {
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 0273029..d667898 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -457,7 +457,7 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
 	 * wait for all outstanding writes, before sending the FSYNC
 	 * request.
 	 */
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(file, start, end);
 	if (err)
 		goto out;
 
@@ -465,10 +465,10 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
 
 	/*
 	 * Due to implementation of fuse writeback
-	 * filemap_write_and_wait_range() does not catch errors.
+	 * file_write_and_wait_range() does not catch errors.
 	 * We have to do this directly after fuse_sync_writes()
 	 */
-	err = filemap_check_errors(file->f_mapping);
+	err = file_check_and_advance_wb_err(file);
 	if (err)
 		goto out;
 
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index bb48074..33a0cb5 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -668,12 +668,14 @@ static int gfs2_fsync(struct file *file, loff_t start, loff_t end,
 		if (ret)
 			return ret;
 		if (gfs2_is_jdata(ip))
-			filemap_write_and_wait(mapping);
+			ret = file_write_and_wait(file);
+		if (ret)
+			return ret;
 		gfs2_ail_flush(ip->i_gl, 1);
 	}
 
 	if (mapping->nrpages)
-		ret = filemap_fdatawait_range(mapping, start, end);
+		ret = file_fdatawait_range(file, start, end);
 
 	return ret ? ret : ret1;
 }
diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
index bfbba79..2538b49 100644
--- a/fs/hfs/inode.c
+++ b/fs/hfs/inode.c
@@ -656,7 +656,7 @@ static int hfs_file_fsync(struct file *filp, loff_t start, loff_t end,
 	struct super_block * sb;
 	int ret, err;
 
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(filp, start, end);
 	if (ret)
 		return ret;
 	inode_lock(inode);
diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index e8638d5..4f26b68 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -283,7 +283,7 @@ int hfsplus_file_fsync(struct file *file, loff_t start, loff_t end,
 	struct hfsplus_sb_info *sbi = HFSPLUS_SB(inode->i_sb);
 	int error = 0, error2;
 
-	error = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	error = file_write_and_wait_range(file, start, end);
 	if (error)
 		return error;
 	inode_lock(inode);
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index e61261a..c148e7f 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -374,7 +374,7 @@ static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
 	struct inode *inode = file->f_mapping->host;
 	int ret;
 
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(file, start, end);
 	if (ret)
 		return ret;
 
diff --git a/fs/hpfs/file.c b/fs/hpfs/file.c
index b3be1b5..f261384 100644
--- a/fs/hpfs/file.c
+++ b/fs/hpfs/file.c
@@ -24,7 +24,7 @@ int hpfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	struct inode *inode = file->f_mapping->host;
 	int ret;
 
-	ret = filemap_write_and_wait_range(file->f_mapping, start, end);
+	ret = file_write_and_wait_range(file, start, end);
 	if (ret)
 		return ret;
 	return sync_blockdev(inode->i_sb->s_bdev);
diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index c12476e..bd0428b 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -35,7 +35,7 @@ int jffs2_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
 	int ret;
 
-	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	ret = file_write_and_wait_range(filp, start, end);
 	if (ret)
 		return ret;
 
diff --git a/fs/jfs/file.c b/fs/jfs/file.c
index 739492c..36665fd 100644
--- a/fs/jfs/file.c
+++ b/fs/jfs/file.c
@@ -34,7 +34,7 @@ int jfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	struct inode *inode = file->f_mapping->host;
 	int rc = 0;
 
-	rc = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	rc = file_write_and_wait_range(file, start, end);
 	if (rc)
 		return rc;
 
diff --git a/fs/ncpfs/file.c b/fs/ncpfs/file.c
index 76965e7..a06c076 100644
--- a/fs/ncpfs/file.c
+++ b/fs/ncpfs/file.c
@@ -23,7 +23,7 @@
 
 static int ncp_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
-	return filemap_write_and_wait_range(file->f_mapping, start, end);
+	return file_write_and_wait_range(file, start, end);
 }
 
 /*
diff --git a/fs/ntfs/dir.c b/fs/ntfs/dir.c
index 0ee19ec..1a24be9 100644
--- a/fs/ntfs/dir.c
+++ b/fs/ntfs/dir.c
@@ -1506,7 +1506,7 @@ static int ntfs_dir_fsync(struct file *filp, loff_t start, loff_t end,
 
 	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 
-	err = filemap_write_and_wait_range(vi->i_mapping, start, end);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 	inode_lock(vi);
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index c4f68c3..331910f 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1989,7 +1989,7 @@ static int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
 
 	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 
-	err = filemap_write_and_wait_range(vi->i_mapping, start, end);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 	inode_lock(vi);
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index bfeb647..66e59d3 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -196,7 +196,7 @@ static int ocfs2_sync_file(struct file *file, loff_t start, loff_t end,
 	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
 		return -EROFS;
 
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(file, start, end);
 	if (err)
 		return err;
 
diff --git a/fs/reiserfs/dir.c b/fs/reiserfs/dir.c
index 45aa05e..5b50689 100644
--- a/fs/reiserfs/dir.c
+++ b/fs/reiserfs/dir.c
@@ -34,7 +34,7 @@ static int reiserfs_dir_fsync(struct file *filp, loff_t start, loff_t end,
 	struct inode *inode = filp->f_mapping->host;
 	int err;
 
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 
diff --git a/fs/reiserfs/file.c b/fs/reiserfs/file.c
index b396eb0..843aadc 100644
--- a/fs/reiserfs/file.c
+++ b/fs/reiserfs/file.c
@@ -154,7 +154,7 @@ static int reiserfs_sync_file(struct file *filp, loff_t start, loff_t end,
 	int err;
 	int barrier_done;
 
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 
diff --git a/fs/sync.c b/fs/sync.c
index 2a54c1f..27d6b8b 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -342,7 +342,7 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 
 	ret = 0;
 	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
-		ret = filemap_fdatawait_range(mapping, offset, endbyte);
+		ret = file_fdatawait_range(f.file, offset, endbyte);
 		if (ret < 0)
 			goto out_put;
 	}
@@ -355,7 +355,7 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 	}
 
 	if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
-		ret = filemap_fdatawait_range(mapping, offset, endbyte);
+		ret = file_fdatawait_range(f.file, offset, endbyte);
 
 out_put:
 	fdput(f);
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 8cad0b1..f90a466 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1337,7 +1337,7 @@ int ubifs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 		 */
 		return 0;
 
-	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	err = file_write_and_wait_range(file, start, end);
 	if (err)
 		return err;
 	inode_lock(inode);
diff --git a/include/linux/errseq.h b/include/linux/errseq.h
index 9e0d444..f746bd8 100644
--- a/include/linux/errseq.h
+++ b/include/linux/errseq.h
@@ -1,18 +1,12 @@
+/*
+ * See Documentation/errseq.rst and lib/errseq.c
+ */
 #ifndef _LINUX_ERRSEQ_H
 #define _LINUX_ERRSEQ_H
 
-/* See lib/errseq.c for more info */
-
 typedef u32	errseq_t;
 
-errseq_t __errseq_set(errseq_t *eseq, int err);
-static inline void errseq_set(errseq_t *eseq, int err)
-{
-	/* Optimize for the common case of no error */
-	if (unlikely(err))
-		__errseq_set(eseq, err);
-}
-
+errseq_t errseq_set(errseq_t *eseq, int err);
 errseq_t errseq_sample(errseq_t *eseq);
 int errseq_check(errseq_t *eseq, errseq_t since);
 int errseq_check_and_advance(errseq_t *eseq, errseq_t *since);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0a51a8b..5b744a3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2544,12 +2544,19 @@ extern int invalidate_inode_pages2_range(struct address_space *mapping,
 extern int write_inode_now(struct inode *, int);
 extern int filemap_fdatawrite(struct address_space *);
 extern int filemap_flush(struct address_space *);
-extern int filemap_fdatawait(struct address_space *);
 extern int filemap_fdatawait_keep_errors(struct address_space *mapping);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
 				   loff_t lend);
+
+static inline int filemap_fdatawait(struct address_space *mapping)
+{
+	return filemap_fdatawait_range(mapping, 0, LLONG_MAX);
+}
+
 extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
 				  loff_t lend);
+extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart,
+						loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
 				        loff_t lstart, loff_t lend);
@@ -2558,12 +2565,19 @@ extern int __filemap_fdatawrite_range(struct address_space *mapping,
 extern int filemap_fdatawrite_range(struct address_space *mapping,
 				loff_t start, loff_t end);
 extern int filemap_check_errors(struct address_space *mapping);
-
 extern void __filemap_set_wb_err(struct address_space *mapping, int err);
+
+extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart,
+						loff_t lend);
 extern int __must_check file_check_and_advance_wb_err(struct file *file);
 extern int __must_check file_write_and_wait_range(struct file *file,
 						loff_t start, loff_t end);
 
+static inline int file_write_and_wait(struct file *file)
+{
+	return file_write_and_wait_range(file, 0, LLONG_MAX);
+}
+
 /**
  * filemap_set_wb_err - set a writeback error on an address_space
  * @mapping: mapping in which to set writeback error
@@ -2577,8 +2591,6 @@ extern int __must_check file_write_and_wait_range(struct file *file,
  * When a writeback error occurs, most filesystems will want to call
  * filemap_set_wb_err to record the error in the mapping so that it will be
  * automatically reported whenever fsync is called on the file.
- *
- * FIXME: mention FS_* flag here?
  */
 static inline void filemap_set_wb_err(struct address_space *mapping, int err)
 {
diff --git a/lib/errseq.c b/lib/errseq.c
index 841fa24..7b900c2 100644
--- a/lib/errseq.c
+++ b/lib/errseq.c
@@ -41,23 +41,20 @@
 #define ERRSEQ_CTR_INC		(1 << (ERRSEQ_SHIFT + 1))
 
 /**
- * __errseq_set - set a errseq_t for later reporting
+ * errseq_set - set a errseq_t for later reporting
  * @eseq: errseq_t field that should be set
- * @err: error to set
+ * @err: error to set (must be between -1 and -MAX_ERRNO)
  *
  * This function sets the error in *eseq, and increments the sequence counter
  * if the last sequence was sampled at some point in the past.
  *
  * Any error set will always overwrite an existing error.
  *
- * Most callers will want to use the errseq_set inline wrapper to efficiently
- * handle the common case where err is 0.
- *
- * We do return an errseq_t here, primarily for debugging purposes. The return
- * value should not be used as a previously sampled value in later calls as it
- * will not have the SEEN flag set.
+ * We do return the latest value here, primarily for debugging purposes. The
+ * return value should not be used as a previously sampled value in later calls
+ * as it will not have the SEEN flag set.
  */
-errseq_t __errseq_set(errseq_t *eseq, int err)
+errseq_t errseq_set(errseq_t *eseq, int err)
 {
 	errseq_t cur, old;
 
@@ -107,7 +104,7 @@ errseq_t __errseq_set(errseq_t *eseq, int err)
 	}
 	return cur;
 }
-EXPORT_SYMBOL(__errseq_set);
+EXPORT_SYMBOL(errseq_set);
 
 /**
  * errseq_sample - grab current errseq_t value
diff --git a/mm/filemap.c b/mm/filemap.c
index 65b4b6e..1e01cb6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -476,6 +476,29 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 EXPORT_SYMBOL(filemap_fdatawait_range);
 
 /**
+ * file_fdatawait_range - wait for writeback to complete
+ * @file:		file pointing to address space structure to wait for
+ * @start_byte:		offset in bytes where the range starts
+ * @end_byte:		offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the address space that file
+ * refers to, in the given range and wait for all of them.  Check error
+ * status of the address space vs. the file->f_wb_err cursor and return it.
+ *
+ * Since the error status of the file is advanced by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ */
+int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
+{
+	struct address_space *mapping = file->f_mapping;
+
+	__filemap_fdatawait_range(mapping, start_byte, end_byte);
+	return file_check_and_advance_wb_err(file);
+}
+EXPORT_SYMBOL(file_fdatawait_range);
+
+/**
  * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
  * @mapping: address space structure to wait for
  *
@@ -489,45 +512,22 @@ EXPORT_SYMBOL(filemap_fdatawait_range);
  */
 int filemap_fdatawait_keep_errors(struct address_space *mapping)
 {
-	loff_t i_size = i_size_read(mapping->host);
-
-	if (i_size == 0)
-		return 0;
-
-	__filemap_fdatawait_range(mapping, 0, i_size - 1);
+	__filemap_fdatawait_range(mapping, 0, LLONG_MAX);
 	return filemap_check_and_keep_errors(mapping);
 }
 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
 
-/**
- * filemap_fdatawait - wait for all under-writeback pages to complete
- * @mapping: address space structure to wait for
- *
- * Walk the list of under-writeback pages of the given address space
- * and wait for all of them.  Check error status of the address space
- * and return it.
- *
- * Since the error status of the address space is cleared by this function,
- * callers are responsible for checking the return value and handling and/or
- * reporting the error.
- */
-int filemap_fdatawait(struct address_space *mapping)
+static bool mapping_needs_writeback(struct address_space *mapping)
 {
-	loff_t i_size = i_size_read(mapping->host);
-
-	if (i_size == 0)
-		return 0;
-
-	return filemap_fdatawait_range(mapping, 0, i_size - 1);
+	return (!dax_mapping(mapping) && mapping->nrpages) ||
+	    (dax_mapping(mapping) && mapping->nrexceptional);
 }
-EXPORT_SYMBOL(filemap_fdatawait);
 
 int filemap_write_and_wait(struct address_space *mapping)
 {
 	int err = 0;
 
-	if ((!dax_mapping(mapping) && mapping->nrpages) ||
-	    (dax_mapping(mapping) && mapping->nrexceptional)) {
+	if (mapping_needs_writeback(mapping)) {
 		err = filemap_fdatawrite(mapping);
 		/*
 		 * Even if the above returned error, the pages may be
@@ -566,8 +566,7 @@ int filemap_write_and_wait_range(struct address_space *mapping,
 {
 	int err = 0;
 
-	if ((!dax_mapping(mapping) && mapping->nrpages) ||
-	    (dax_mapping(mapping) && mapping->nrexceptional)) {
+	if (mapping_needs_writeback(mapping)) {
 		err = __filemap_fdatawrite_range(mapping, lstart, lend,
 						 WB_SYNC_ALL);
 		/* See comment of filemap_write_and_wait() */
@@ -589,7 +588,7 @@ EXPORT_SYMBOL(filemap_write_and_wait_range);
 
 void __filemap_set_wb_err(struct address_space *mapping, int err)
 {
-	errseq_t eseq = __errseq_set(&mapping->wb_err, err);
+	errseq_t eseq = errseq_set(&mapping->wb_err, err);
 
 	trace_filemap_set_wb_err(mapping, eseq);
 }
@@ -656,8 +655,7 @@ int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
 	int err = 0, err2;
 	struct address_space *mapping = file->f_mapping;
 
-	if ((!dax_mapping(mapping) && mapping->nrpages) ||
-	    (dax_mapping(mapping) && mapping->nrexceptional)) {
+	if (mapping_needs_writeback(mapping)) {
 		err = __filemap_fdatawrite_range(mapping, lstart, lend,
 						 WB_SYNC_ALL);
 		/* See comment of filemap_write_and_wait() */