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gfs2: Explain some direct I/O oddities

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Add some comments explaining the oddities of partial direct I/O reads
and writes.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2022-04-26 23:31:06 +02:00
parent b846f2d7e2
commit 53bb540fd5
1 changed files with 4 additions and 0 deletions
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4
fs/gfs2/file.c
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@ -840,6 +840,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to,
pagefault_enable();
if (ret <= 0 && ret != -EFAULT)
goto out_unlock;
/* No increment (+=) because iomap_dio_rw returns a cumulative value. */
if (ret > 0)
read = ret;
@ -854,6 +855,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to,
gfs2_glock_dq(gh);
out_uninit:
gfs2_holder_uninit(gh);
/* User space doesn't expect partial success. */
if (ret < 0)
return ret;
return read;
@ -906,6 +908,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
if (ret != -EFAULT)
goto out_unlock;
}
/* No increment (+=) because iomap_dio_rw returns a cumulative value. */
if (ret > 0)
written = ret;
@ -920,6 +923,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
gfs2_glock_dq(gh);
out_uninit:
gfs2_holder_uninit(gh);
/* User space doesn't expect partial success. */
if (ret < 0)
return ret;
return written;