Re: [PATCH] ext2: preserve IOMAP_F_DIRTY for extending direct writes

[sashiko-bot@kernel.org]

> 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.
> 
> Initialize iomap->flags before setting IOMAP_F_DIRTY so that the flag
> survives and the required metadata synchronization takes place.
> 
> Fixes: fb5de4358e1a ("ext2: Move direct-io to use iomap")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>

Sashiko has reviewed this patch and found no issues.

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