This patch converts ext2 direct-io path to iomap interface.
- This also takes care of DIO_SKIP_HOLES part in which we return -ENOTBLK
from ext2_iomap_begin(), in case if the write is done on a hole.
- This fallbacks to buffered-io in case of DIO_SKIP_HOLES or in case of
a partial write or if any error is detected in ext2_iomap_end().
We try to return -ENOTBLK in such cases.
- For any unaligned or extending DIO writes, we pass
IOMAP_DIO_FORCE_WAIT flag to ensure synchronous writes.
- For extending writes we set IOMAP_F_DIRTY in ext2_iomap_begin because
otherwise with dsync writes on devices that support FUA, generic_write_sync
won't be called and we might miss inode metadata updates.
- Since ext2 already now uses _nolock vartiant of sync write. Hence
there is no inode lock problem with iomap in this patch.
- ext2_iomap_ops are now being shared by DIO, DAX & fiemap path
Tested-by: Disha Goel <disgoel@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
---
fs/ext2/ext2.h | 1 +
fs/ext2/file.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/ext2/inode.c | 53 ++++++++++++++--------
3 files changed, 150 insertions(+), 19 deletions(-)
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index cb78d7dcfb95..00168447d48c 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -753,6 +753,7 @@ extern unsigned long ext2_count_free (struct buffer_head *, unsigned);
extern struct inode *ext2_iget (struct super_block *, unsigned long);
extern int ext2_write_inode (struct inode *, struct writeback_control *);
extern void ext2_evict_inode(struct inode *);
+void ext2_write_failed(struct address_space *mapping, loff_t to);
extern int ext2_get_block(struct inode *, sector_t, struct buffer_head *, int);
extern int ext2_setattr (struct mnt_idmap *, struct dentry *, struct iattr *);
extern int ext2_getattr (struct mnt_idmap *, const struct path *,
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 749163787139..98add36c1a59 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -162,12 +162,124 @@ int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync)
return ret;
}
+static ssize_t ext2_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ ssize_t ret;
+
+ inode_lock_shared(inode);
+ ret = iomap_dio_rw(iocb, to, &ext2_iomap_ops, NULL, 0, NULL, 0);
+ inode_unlock_shared(inode);
+
+ return ret;
+}
+
+static int ext2_dio_write_end_io(struct kiocb *iocb, ssize_t size,
+ int error, unsigned int flags)
+{
+ loff_t pos = iocb->ki_pos;
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ if (error)
+ goto out;
+
+ /*
+ * If we are extending the file, we have to update i_size here before
+ * page cache gets invalidated in iomap_dio_rw(). This prevents racing
+ * buffered reads from zeroing out too much from page cache pages.
+ * Note that all extending writes always happens synchronously with
+ * inode lock held by ext2_dio_write_iter(). So it is safe to update
+ * inode size here for extending file writes.
+ */
+ pos += size;
+ if (pos > i_size_read(inode)) {
+ i_size_write(inode, pos);
+ mark_inode_dirty(inode);
+ }
+out:
+ return error;
+}
+
+static const struct iomap_dio_ops ext2_dio_write_ops = {
+ .end_io = ext2_dio_write_end_io,
+};
+
+static ssize_t ext2_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ ssize_t ret;
+ unsigned int flags = 0;
+ unsigned long blocksize = inode->i_sb->s_blocksize;
+ loff_t offset = iocb->ki_pos;
+ loff_t count = iov_iter_count(from);
+
+ inode_lock(inode);
+ ret = generic_write_checks(iocb, from);
+ if (ret <= 0)
+ goto out_unlock;
+
+ ret = kiocb_modified(iocb);
+ if (ret)
+ goto out_unlock;
+
+ /* use IOMAP_DIO_FORCE_WAIT for unaligned or extending writes */
+ if (iocb->ki_pos + iov_iter_count(from) > i_size_read(inode) ||
+ (!IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(from), blocksize)))
+ flags |= IOMAP_DIO_FORCE_WAIT;
+
+ ret = iomap_dio_rw(iocb, from, &ext2_iomap_ops, &ext2_dio_write_ops,
+ flags, NULL, 0);
+
+ /* ENOTBLK is magic return value for fallback to buffered-io */
+ if (ret == -ENOTBLK)
+ ret = 0;
+
+ if (ret < 0 && ret != -EIOCBQUEUED)
+ ext2_write_failed(inode->i_mapping, offset + count);
+
+ /* handle case for partial write and for fallback to buffered write */
+ if (ret >= 0 && iov_iter_count(from)) {
+ loff_t pos, endbyte;
+ ssize_t status;
+ int ret2;
+
+ iocb->ki_flags &= ~IOCB_DIRECT;
+ pos = iocb->ki_pos;
+ status = generic_perform_write(iocb, from);
+ if (unlikely(status < 0)) {
+ ret = status;
+ goto out_unlock;
+ }
+
+ iocb->ki_pos += status;
+ ret += status;
+ endbyte = pos + status - 1;
+ ret2 = filemap_write_and_wait_range(inode->i_mapping, pos,
+ endbyte);
+ if (!ret2)
+ invalidate_mapping_pages(inode->i_mapping,
+ pos >> PAGE_SHIFT,
+ endbyte >> PAGE_SHIFT);
+ if (ret > 0)
+ generic_write_sync(iocb, ret);
+ }
+
+out_unlock:
+ inode_unlock(inode);
+ return ret;
+}
+
static ssize_t ext2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
#ifdef CONFIG_FS_DAX
if (IS_DAX(iocb->ki_filp->f_mapping->host))
return ext2_dax_read_iter(iocb, to);
#endif
+ if (iocb->ki_flags & IOCB_DIRECT)
+ return ext2_dio_read_iter(iocb, to);
+
return generic_file_read_iter(iocb, to);
}
@@ -177,6 +289,9 @@ static ssize_t ext2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (IS_DAX(iocb->ki_filp->f_mapping->host))
return ext2_dax_write_iter(iocb, from);
#endif
+ if (iocb->ki_flags & IOCB_DIRECT)
+ return ext2_dio_write_iter(iocb, from);
+
return generic_file_write_iter(iocb, from);
}
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index dc76147e7b07..75983215c7a1 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -56,7 +56,7 @@ static inline int ext2_inode_is_fast_symlink(struct inode *inode)
static void ext2_truncate_blocks(struct inode *inode, loff_t offset);
-static void ext2_write_failed(struct address_space *mapping, loff_t to)
+void ext2_write_failed(struct address_space *mapping, loff_t to)
{
struct inode *inode = mapping->host;
@@ -809,9 +809,27 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
bool new = false, boundary = false;
u32 bno;
int ret;
+ bool create = flags & IOMAP_WRITE;
+
+ /*
+ * For writes that could fill holes inside i_size on a
+ * DIO_SKIP_HOLES filesystem we forbid block creations: only
+ * overwrites are permitted.
+ */
+ if ((flags & IOMAP_DIRECT) &&
+ (first_block << blkbits) < i_size_read(inode))
+ create = 0;
+
+ /*
+ * Writes that span EOF might trigger an IO size update on completion,
+ * so consider them to be dirty for the purposes of O_DSYNC even if
+ * there is no other metadata changes pending or have been made here.
+ */
+ if ((flags & IOMAP_WRITE) && offset + length > i_size_read(inode))
+ iomap->flags |= IOMAP_F_DIRTY;
ret = ext2_get_blocks(inode, first_block, max_blocks,
- &bno, &new, &boundary, flags & IOMAP_WRITE);
+ &bno, &new, &boundary, create);
if (ret < 0)
return ret;
@@ -823,6 +841,12 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
iomap->bdev = inode->i_sb->s_bdev;
if (ret == 0) {
+ /*
+ * Switch to buffered-io for writing to holes in a non-extent
+ * based filesystem to avoid stale data exposure problem.
+ */
+ if (!create && (flags & IOMAP_WRITE) && (flags & IOMAP_DIRECT))
+ return -ENOTBLK;
iomap->type = IOMAP_HOLE;
iomap->addr = IOMAP_NULL_ADDR;
iomap->length = 1 << blkbits;
@@ -844,6 +868,13 @@ static int
ext2_iomap_end(struct inode *inode, loff_t offset, loff_t length,
ssize_t written, unsigned flags, struct iomap *iomap)
{
+ /*
+ * Switch to buffered-io in case of any error.
+ * Blocks allocated can be used by the buffered-io path.
+ */
+ if ((flags & IOMAP_DIRECT) && (flags & IOMAP_WRITE) && written == 0)
+ return -ENOTBLK;
+
if (iomap->type == IOMAP_MAPPED &&
written < length &&
(flags & IOMAP_WRITE))
@@ -908,22 +939,6 @@ static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
return generic_block_bmap(mapping,block,ext2_get_block);
}
-static ssize_t
-ext2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
-{
- struct file *file = iocb->ki_filp;
- struct address_space *mapping = file->f_mapping;
- struct inode *inode = mapping->host;
- size_t count = iov_iter_count(iter);
- loff_t offset = iocb->ki_pos;
- ssize_t ret;
-
- ret = blockdev_direct_IO(iocb, inode, iter, ext2_get_block);
- if (ret < 0 && iov_iter_rw(iter) == WRITE)
- ext2_write_failed(mapping, offset + count);
- return ret;
-}
-
static int
ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
@@ -946,7 +961,7 @@ const struct address_space_operations ext2_aops = {
.write_begin = ext2_write_begin,
.write_end = ext2_write_end,
.bmap = ext2_bmap,
- .direct_IO = ext2_direct_IO,
+ .direct_IO = noop_direct_IO,
.writepages = ext2_writepages,
.migrate_folio = buffer_migrate_folio,
.is_partially_uptodate = block_is_partially_uptodate,
--
2.39.2
