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ext2: preserve IOMAP_F_DIRTY for extending direct writes

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ext2_iomap_begin() sets IOMAP_F_DIRTY for writes that may extend i_size,
but clears the flag after ext2_get_blocks(). When the write uses an
existing mapped block, iomap can then use FUA and skip
generic_write_sync(), even though ext2_dio_write_end_io() updates the
inode size. An O_DSYNC write can therefore return without persisting
the new size.

For example, on a FUA-capable device, a 512-byte O_DIRECT|O_DSYNC write
at offset 512 into a fsynced one-byte file returns successfully and
extends the in-memory size to 1024, while an immediate read of the
on-disk inode still shows size 1. An explicit fsync persists the new
size.

Move setting of IOMAP_F_DIRTY after the initialization.

Fixes: fb5de4358e ("ext2: Move direct-io to use iomap")
Cc: stable@vger.kernel.org
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
Link: https://patch.msgid.link/20261029013616.97194-1-dennylin0707@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Hungyu Lin 2026-10-29 01:36:16 +00:00 committed by Jan Kara
parent d4a6efef3e
commit 4f91b042af
1 changed files with 6 additions and 7 deletions
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13
fs/ext2/inode.c
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@ -807,6 +807,12 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
(first_block << blkbits) < i_size_read(inode))
create = 0;
ret = ext2_get_blocks(inode, first_block, max_blocks,
&bno, &new, &boundary, create);
if (ret < 0)
return ret;
iomap->flags = 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
@ -814,13 +820,6 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
*/
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, create);
if (ret < 0)
return ret;
iomap->flags = 0;
iomap->offset = (u64)first_block << blkbits;
iomap->bdev = inode->i_sb->s_bdev;