[PATCH] fs/ceph/io: make ceph_start_io_*() killable

[Max Kellermann <max.kellermann@xxxxxxxxx>]

This allows killing processes that wait for a lock when one process is
stuck waiting for the Ceph server.  This is similar to the NFS commit
38a125b31504 ("fs/nfs/io: make nfs_start_io_*() killable").

Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
---
 fs/ceph/file.c | 22 +++++++++++++---------
 fs/ceph/io.c   | 44 +++++++++++++++++++++++++++++++++-----------
 fs/ceph/io.h   |  8 +++++---
 3 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 4b8d59ebda00..d79c0774dc6e 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -2127,10 +2127,11 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	if (ceph_inode_is_shutdown(inode))
 		return -ESTALE;
 
-	if (direct_lock)
-		ceph_start_io_direct(inode);
-	else
-		ceph_start_io_read(inode);
+	ret = direct_lock
+		? ceph_start_io_direct(inode)
+		: ceph_start_io_read(inode);
+	if (ret)
+		return ret;
 
 	if (!(fi->flags & CEPH_F_SYNC) && !direct_lock)
 		want |= CEPH_CAP_FILE_CACHE;
@@ -2283,7 +2284,9 @@ static ssize_t ceph_splice_read(struct file *in, loff_t *ppos,
 	    (fi->flags & CEPH_F_SYNC))
 		return copy_splice_read(in, ppos, pipe, len, flags);
 
-	ceph_start_io_read(inode);
+	ret = ceph_start_io_read(inode);
+	if (ret)
+		return ret;
 
 	want = CEPH_CAP_FILE_CACHE;
 	if (fi->fmode & CEPH_FILE_MODE_LAZY)
@@ -2362,10 +2365,11 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		direct_lock = true;
 
 retry_snap:
-	if (direct_lock)
-		ceph_start_io_direct(inode);
-	else
-		ceph_start_io_write(inode);
+	err = direct_lock
+		? ceph_start_io_direct(inode)
+		: ceph_start_io_write(inode);
+	if (err)
+		goto out_unlocked;
 
 	if (iocb->ki_flags & IOCB_APPEND) {
 		err = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
diff --git a/fs/ceph/io.c b/fs/ceph/io.c
index c456509b31c3..2735503bc479 100644
--- a/fs/ceph/io.c
+++ b/fs/ceph/io.c
@@ -47,20 +47,30 @@ static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode)
  * Note that buffered writes and truncates both take a write lock on
  * inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
  */
-void
+int
 ceph_start_io_read(struct inode *inode)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
+	int err;
 
 	/* Be an optimist! */
-	down_read(&inode->i_rwsem);
+	err = down_read_killable(&inode->i_rwsem);
+	if (err)
+		return err;
+
 	if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT))
-		return;
+		return 0;
 	up_read(&inode->i_rwsem);
+
 	/* Slow path.... */
-	down_write(&inode->i_rwsem);
+	err = down_write_killable(&inode->i_rwsem);
+	if (err)
+		return err;
+
 	ceph_block_o_direct(ci, inode);
 	downgrade_write(&inode->i_rwsem);
+
+	return 0;
 }
 
 /**
@@ -83,11 +93,13 @@ ceph_end_io_read(struct inode *inode)
  * Declare that a buffered write operation is about to start, and ensure
  * that we block all direct I/O.
  */
-void
+int
 ceph_start_io_write(struct inode *inode)
 {
-	down_write(&inode->i_rwsem);
-	ceph_block_o_direct(ceph_inode(inode), inode);
+	int err = down_write_killable(&inode->i_rwsem);
+	if (!err)
+		ceph_block_o_direct(ceph_inode(inode), inode);
+	return err;
 }
 
 /**
@@ -133,20 +145,30 @@ static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode)
  * Note that buffered writes and truncates both take a write lock on
  * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
  */
-void
+int
 ceph_start_io_direct(struct inode *inode)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
+	int err;
 
 	/* Be an optimist! */
-	down_read(&inode->i_rwsem);
+	err = down_read_killable(&inode->i_rwsem);
+	if (err)
+		return err;
+
 	if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)
-		return;
+		return 0;
 	up_read(&inode->i_rwsem);
+
 	/* Slow path.... */
-	down_write(&inode->i_rwsem);
+	err = down_write_killable(&inode->i_rwsem);
+	if (err)
+		return err;
+
 	ceph_block_buffered(ci, inode);
 	downgrade_write(&inode->i_rwsem);
+
+	return 0;
 }
 
 /**
diff --git a/fs/ceph/io.h b/fs/ceph/io.h
index fa594cd77348..08d58253f533 100644
--- a/fs/ceph/io.h
+++ b/fs/ceph/io.h
@@ -2,11 +2,13 @@
 #ifndef _FS_CEPH_IO_H
 #define _FS_CEPH_IO_H
 
-void ceph_start_io_read(struct inode *inode);
+#include <linux/compiler_attributes.h> // for __must_check
+
+__must_check int ceph_start_io_read(struct inode *inode);
 void ceph_end_io_read(struct inode *inode);
-void ceph_start_io_write(struct inode *inode);
+__must_check int ceph_start_io_write(struct inode *inode);
 void ceph_end_io_write(struct inode *inode);
-void ceph_start_io_direct(struct inode *inode);
+__must_check int ceph_start_io_direct(struct inode *inode);
 void ceph_end_io_direct(struct inode *inode);
 
 #endif /* FS_CEPH_IO_H */
-- 
2.45.2