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H A D | shmem.c | diff 1bdec44b1eee32e311b44b5b06144bb7d9b33938 Thu Apr 14 21:13:27 CDT 2022 Hugh Dickins <hughd@google.com> tmpfs: fix regressions from wider use of ZERO_PAGE
Chuck Lever reported fsx-based xfstests generic 075 091 112 127 failing when 5.18-rc1 NFS server exports tmpfs: bisected to recent tmpfs change.
Whilst nfsd_splice_action() does contain some questionable handling of repeated pages, and Chuck was able to work around there, history from Mark Hemment makes clear that there might be similar dangers elsewhere: it was not a good idea for me to pass ZERO_PAGE down to unknown actors.
Revert shmem_file_read_iter() to using ZERO_PAGE for holes only when iter_is_iovec(); in other cases, use the more natural iov_iter_zero() instead of copy_page_to_iter().
We would use iov_iter_zero() throughout, but the x86 clear_user() is not nearly so well optimized as copy to user (dd of 1T sparse tmpfs file takes 57 seconds rather than 44 seconds).
And now pagecache_init() does not need to SetPageUptodate(ZERO_PAGE(0)): which had caused boot failure on arm noMMU STM32F7 and STM32H7 boards
Link: https://lkml.kernel.org/r/9a978571-8648-e830-5735-1f4748ce2e30@google.com Fixes: 56a8c8eb1eaf ("tmpfs: do not allocate pages on read") Signed-off-by: Hugh Dickins <hughd@google.com> Reported-by: Patrice CHOTARD <patrice.chotard@foss.st.com> Reported-by: Chuck Lever III <chuck.lever@oracle.com> Tested-by: Chuck Lever III <chuck.lever@oracle.com> Cc: Mark Hemment <markhemm@googlemail.com> Cc: Patrice CHOTARD <patrice.chotard@foss.st.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Lukas Czerner <lczerner@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: "Darrick J. Wong" <djwong@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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H A D | filemap.c | diff 1bdec44b1eee32e311b44b5b06144bb7d9b33938 Thu Apr 14 21:13:27 CDT 2022 Hugh Dickins <hughd@google.com> tmpfs: fix regressions from wider use of ZERO_PAGE
Chuck Lever reported fsx-based xfstests generic 075 091 112 127 failing when 5.18-rc1 NFS server exports tmpfs: bisected to recent tmpfs change.
Whilst nfsd_splice_action() does contain some questionable handling of repeated pages, and Chuck was able to work around there, history from Mark Hemment makes clear that there might be similar dangers elsewhere: it was not a good idea for me to pass ZERO_PAGE down to unknown actors.
Revert shmem_file_read_iter() to using ZERO_PAGE for holes only when iter_is_iovec(); in other cases, use the more natural iov_iter_zero() instead of copy_page_to_iter().
We would use iov_iter_zero() throughout, but the x86 clear_user() is not nearly so well optimized as copy to user (dd of 1T sparse tmpfs file takes 57 seconds rather than 44 seconds).
And now pagecache_init() does not need to SetPageUptodate(ZERO_PAGE(0)): which had caused boot failure on arm noMMU STM32F7 and STM32H7 boards
Link: https://lkml.kernel.org/r/9a978571-8648-e830-5735-1f4748ce2e30@google.com Fixes: 56a8c8eb1eaf ("tmpfs: do not allocate pages on read") Signed-off-by: Hugh Dickins <hughd@google.com> Reported-by: Patrice CHOTARD <patrice.chotard@foss.st.com> Reported-by: Chuck Lever III <chuck.lever@oracle.com> Tested-by: Chuck Lever III <chuck.lever@oracle.com> Cc: Mark Hemment <markhemm@googlemail.com> Cc: Patrice CHOTARD <patrice.chotard@foss.st.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Lukas Czerner <lczerner@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: "Darrick J. Wong" <djwong@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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