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netfs: fix error handling in netfs_extract_user_iter()

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In netfs_extract_user_iter(), if iov_iter_extract_pages() failed to
extract user pages, bail out on -ENOMEM, otherwise return the error
code only if @npages == 0, allowing short DIO reads and writes to be
issued.

This fixes mmapstress02 from LTP tests against CIFS.

Fixes: 85dd2c8ff3 ("netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator")
Reported-by: Xiaoli Feng <xifeng@redhat.com>
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260512123404.719402-10-dhowells@redhat.com
Cc: netfs@lists.linux.dev
Cc: stable@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Paulo Alcantara 2026-05-12 13:33:46 +01:00 committed by Christian Brauner
parent 7e3d8db899
commit 0aad5704c6
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 10 additions and 3 deletions
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13
fs/netfs/iterator.c
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@ -22,7 +22,7 @@
*
* Extract the page fragments from the given amount of the source iterator and
* build up a second iterator that refers to all of those bits. This allows
* the original iterator to disposed of.
* the original iterator to be disposed of.
*
* @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be
* allowed on the pages extracted.
@ -67,8 +67,8 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
ret = iov_iter_extract_pages(orig, &pages, count,
max_pages - npages, extraction_flags,
&offset);
if (ret < 0) {
pr_err("Couldn't get user pages (rc=%zd)\n", ret);
if (unlikely(ret <= 0)) {
ret = ret ?: -EIO;
break;
}
@ -97,6 +97,13 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
npages += cur_npages;
}
if (ret < 0 && (ret == -ENOMEM || npages == 0)) {
for (i = 0; i < npages; i++)
unpin_user_page(bv[i].bv_page);
kvfree(bv);
return ret;
}
iov_iter_bvec(new, orig->data_source, bv, npages, orig_len - count);
return npages;
}