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Wong" To: "Pankaj Raghav (Samsung)" Cc: david@fromorbit.com, willy@infradead.org, chandan.babu@oracle.com, brauner@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, yang@os.amperecomputing.com, linux-mm@kvack.org, john.g.garry@oracle.com, linux-fsdevel@vger.kernel.org, hare@suse.de, p.raghav@samsung.com, mcgrof@kernel.org, gost.dev@samsung.com, cl@os.amperecomputing.com, linux-xfs@vger.kernel.org, hch@lst.de, Zi Yan Subject: Re: [PATCH v8 05/10] filemap: cap PTE range to be created to allowed zero fill in folio_map_range() Message-ID: <20240701233924.GG612460@frogsfrogsfrogs> References: <20240625114420.719014-1-kernel@pankajraghav.com> <20240625114420.719014-6-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240625114420.719014-6-kernel@pankajraghav.com> X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: ED7B7C000D X-Stat-Signature: x1iwh1qqdtc4ndr4tmmg1y5drqmj7etg X-HE-Tag: 1719877165-507513 X-HE-Meta: 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 cTe76ZW2 iJUdUOYsNIYkYmLM3Es0+Hv0SLVRsCJqYjTksQVca8N2PV2j888/AcXY4OAPR82JG/iI/l/V6DaE4NiWpkxlujDY/8J9cATUGFVYWWMFrhSzzboA8cegm2owxzXKLCsbd+sNGBafP/SlwQOikZ56NG6P8afIEypCwUMGVsRdJrcVGRH1oMMUS9EjiIqjas3SYCdTABiqfxZF/I/Dm3YO6WAHp+e0D8jJA87IEUae0B+wz3MNyfFmQ9gqlGh7I/kx5lNYT5kResPTCQMBfBOMNhOyJXnsQ8glaSoYYYyoWanYZo+Izd3ZNQKCjaTVmql64oEI+GYnhwd7FwbInWXZFhi6zLV6JAdnp1R5UIKDUhHAzUEU0pU2Y7fFPm7JYu56NlbwMvY4U2H8KpniPCnm5xoe3KCrtPIcKQ+88 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 25, 2024 at 11:44:15AM +0000, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav > > Usually the page cache does not extend beyond the size of the inode, > therefore, no PTEs are created for folios that extend beyond the size. > > But with LBS support, we might extend page cache beyond the size of the > inode as we need to guarantee folios of minimum order. While doing a > read, do_fault_around() can create PTEs for pages that lie beyond the > EOF leading to incorrect error return when accessing a page beyond the > mapped file. > > Cap the PTE range to be created for the page cache up to the end of > file(EOF) in filemap_map_pages() so that return error codes are consistent > with POSIX[1] for LBS configurations. > > generic/749(currently in xfstest-dev patches-in-queue branch [0]) has > been created to trigger this edge case. This also fixes generic/749 for > tmpfs with huge=always on systems with 4k base page size. > > [0] https://lore.kernel.org/all/20240615002935.1033031-3-mcgrof@kernel.org/ > [1](from mmap(2)) SIGBUS > Attempted access to a page of the buffer that lies beyond the end > of the mapped file. For an explanation of the treatment of the > bytes in the page that corresponds to the end of a mapped file > that is not a multiple of the page size, see NOTES. > > Signed-off-by: Luis Chamberlain > Signed-off-by: Pankaj Raghav > Reviewed-by: Hannes Reinecke > Reviewed-by: Matthew Wilcox (Oracle) Heh, another fun mmap wart! Reviewed-by: Darrick J. Wong --D > --- > mm/filemap.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 8eafbd4a4d0c..56ff1d936aa8 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -3612,7 +3612,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, > struct vm_area_struct *vma = vmf->vma; > struct file *file = vma->vm_file; > struct address_space *mapping = file->f_mapping; > - pgoff_t last_pgoff = start_pgoff; > + pgoff_t file_end, last_pgoff = start_pgoff; > unsigned long addr; > XA_STATE(xas, &mapping->i_pages, start_pgoff); > struct folio *folio; > @@ -3638,6 +3638,10 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, > goto out; > } > > + file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1; > + if (end_pgoff > file_end) > + end_pgoff = file_end; > + > folio_type = mm_counter_file(folio); > do { > unsigned long end; > -- > 2.44.1 > >