| Message ID | 20230421214400.2836131-3-mcgrof@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | shmem: add support for blocksize > PAGE_SIZE | expand |
On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > The PageHWPoison() call can be converted over to the respective folio call > folio_test_hwpoison(). This introduces no functional changes. Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. Individual pages are hwpoisoned. You're only testing the head page if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to test if _any_ page in the folio is poisoned. But blindly converting PageHWPoison to folio_test_hwpoison() is wrong. If anyone knows how to poison folio_test_hwpoison() to make it not work, I'd appreciate it. > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> > --- > mm/shmem.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 5bf92d571092..6f117c3cbe89 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3483,7 +3483,7 @@ static const char *shmem_get_link(struct dentry *dentry, > folio = filemap_get_folio(inode->i_mapping, 0); > if (IS_ERR(folio)) > return ERR_PTR(-ECHILD); > - if (PageHWPoison(folio_page(folio, 0)) || > + if (folio_test_hwpoison(folio) || > !folio_test_uptodate(folio)) { > folio_put(folio); > return ERR_PTR(-ECHILD); > @@ -3494,7 +3494,7 @@ static const char *shmem_get_link(struct dentry *dentry, > return ERR_PTR(error); > if (!folio) > return ERR_PTR(-ECHILD); > - if (PageHWPoison(folio_page(folio, 0))) { > + if (folio_test_hwpoison(folio)) { > folio_unlock(folio); > folio_put(folio); > return ERR_PTR(-ECHILD); > @@ -4672,7 +4672,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, > return &folio->page; > > page = folio_file_page(folio, index); > - if (PageHWPoison(page)) { > + if (folio_test_hwpoison(folio)) { > folio_put(folio); > return ERR_PTR(-EIO); > } > -- > 2.39.2 >
On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > The PageHWPoison() call can be converted over to the respective folio call > > folio_test_hwpoison(). This introduces no functional changes. > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > Individual pages are hwpoisoned. You're only testing the head page > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > test if _any_ page in the folio is poisoned. But blindly converting > PageHWPoison to folio_test_hwpoison() is wrong. Thanks! I don't see folio_has_hwpoisoned() though. Luis
On Fri, Apr 21, 2023 at 8:05 PM Luis Chamberlain <mcgrof@kernel.org> wrote: > > On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > > The PageHWPoison() call can be converted over to the respective folio call > > > folio_test_hwpoison(). This introduces no functional changes. > > > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > > > Individual pages are hwpoisoned. You're only testing the head page > > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > > test if _any_ page in the folio is poisoned. But blindly converting > > PageHWPoison to folio_test_hwpoison() is wrong. > > Thanks! I don't see folio_has_hwpoisoned() though. We do have PageHasHWPoisoned(), which indicates at least one subpage is hwpoisoned in the huge page. You may need to add a folio variant. > > Luis >
On Mon, Apr 24, 2023 at 02:17:12PM -0700, Yang Shi wrote: > On Fri, Apr 21, 2023 at 8:05 PM Luis Chamberlain <mcgrof@kernel.org> wrote: > > > > On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > > > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > > > The PageHWPoison() call can be converted over to the respective folio call > > > > folio_test_hwpoison(). This introduces no functional changes. > > > > > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > > > > > Individual pages are hwpoisoned. You're only testing the head page > > > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > > > test if _any_ page in the folio is poisoned. But blindly converting > > > PageHWPoison to folio_test_hwpoison() is wrong. > > > > Thanks! I don't see folio_has_hwpoisoned() though. > > We do have PageHasHWPoisoned(), which indicates at least one subpage > is hwpoisoned in the huge page. > > You may need to add a folio variant. PAGEFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) TESTSCFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) That generates folio_has_hwpoisoned() along with folio_set_has_hwpoisoned(), folio_clear_has_hwpoisoned(), folio_test_set_has_hwpoisoned() and folio_test_clear_has_hwpoisoned().
On Mon, Apr 24, 2023 at 2:37 PM Matthew Wilcox <willy@infradead.org> wrote: > > On Mon, Apr 24, 2023 at 02:17:12PM -0700, Yang Shi wrote: > > On Fri, Apr 21, 2023 at 8:05 PM Luis Chamberlain <mcgrof@kernel.org> wrote: > > > > > > On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > > > > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > > > > The PageHWPoison() call can be converted over to the respective folio call > > > > > folio_test_hwpoison(). This introduces no functional changes. > > > > > > > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > > > > > > > Individual pages are hwpoisoned. You're only testing the head page > > > > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > > > > test if _any_ page in the folio is poisoned. But blindly converting > > > > PageHWPoison to folio_test_hwpoison() is wrong. > > > > > > Thanks! I don't see folio_has_hwpoisoned() though. > > > > We do have PageHasHWPoisoned(), which indicates at least one subpage > > is hwpoisoned in the huge page. > > > > You may need to add a folio variant. > > PAGEFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) > TESTSCFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) > > That generates folio_has_hwpoisoned() along with > folio_set_has_hwpoisoned(), folio_clear_has_hwpoisoned(), > folio_test_set_has_hwpoisoned() and folio_test_clear_has_hwpoisoned(). Oh, yeah, I missed that part. Thanks.
On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > The PageHWPoison() call can be converted over to the respective folio call > > folio_test_hwpoison(). This introduces no functional changes. > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > Individual pages are hwpoisoned. You're only testing the head page > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > test if _any_ page in the folio is poisoned. But blindly converting > PageHWPoison to folio_test_hwpoison() is wrong. I see a pattern in shmem.c where first the head is tested and for large folios, any of pages in the folio is tested for poison flag. Should we factor it out as a helper in shmem.c and use it here? static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, ... if (folio_test_hwpoison(folio) || (folio_test_large(folio) && folio_test_has_hwpoisoned(folio))) { .. > > If anyone knows how to poison folio_test_hwpoison() to make it not > work, I'd appreciate it. IMO, I think it will be clear if folio_test_hwpoison checks if any of the page in the folio is poisoned and we should have a explicit helper such as folio_test_head_hwpoison if the callers want to only test if the head page is poisoned (although I am not sure if that is useful).
On Tue, Apr 25, 2023 at 01:00:25PM +0200, Pankaj Raghav wrote: > On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > > The PageHWPoison() call can be converted over to the respective folio call > > > folio_test_hwpoison(). This introduces no functional changes. > > > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > > > Individual pages are hwpoisoned. You're only testing the head page > > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > > test if _any_ page in the folio is poisoned. But blindly converting > > PageHWPoison to folio_test_hwpoison() is wrong. > > I see a pattern in shmem.c where first the head is tested and for large > folios, any of pages in the folio is tested for poison flag. Should we > factor it out as a helper in shmem.c and use it here? > > static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, > ... > if (folio_test_hwpoison(folio) || > (folio_test_large(folio) && > folio_test_has_hwpoisoned(folio))) { > .. Hugh's commit 72887c976a7c9e ("shmem: minor fixes to splice-read implementation") is on point about this : "Perhaps that ugliness can be improved at the mm end later" So how about we put some lipstick on this guy now (notice right above it a similar compound page check for is_page_hwpoison()): diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 1c68d67b832f..6a4a571dbe50 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -883,6 +883,13 @@ static inline bool is_page_hwpoison(struct page *page) return PageHuge(page) && PageHWPoison(compound_head(page)); } +static inline bool is_folio_hwpoison(struct folio *folio) +{ + if (folio_test_hwpoison(folio)) + return true; + return folio_test_large(folio) && folio_test_has_hwpoisoned(folio); +} + /* * For pages that are never mapped to userspace (and aren't PageSlab), * page_type may be used. Because it is initialised to -1, we invert the diff --git a/mm/shmem.c b/mm/shmem.c index ef7ad684f4fb..b7f47f6b75d5 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3013,9 +3013,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, if (folio) { folio_unlock(folio); - if (folio_test_hwpoison(folio) || - (folio_test_large(folio) && - folio_test_has_hwpoisoned(folio))) { + if (is_folio_hwpoison(folio)) { error = -EIO; break; }
On Tue, Apr 25, 2023 at 03:47:24PM -0700, Luis Chamberlain wrote: > On Tue, Apr 25, 2023 at 01:00:25PM +0200, Pankaj Raghav wrote: > > On Fri, Apr 21, 2023 at 11:42:53PM +0100, Matthew Wilcox wrote: > > > On Fri, Apr 21, 2023 at 02:43:54PM -0700, Luis Chamberlain wrote: > > > > The PageHWPoison() call can be converted over to the respective folio call > > > > folio_test_hwpoison(). This introduces no functional changes. > > > > > > Um, no. Nobody should use folio_test_hwpoison(), it's a nonsense. > > > > > > Individual pages are hwpoisoned. You're only testing the head page > > > if you use folio_test_hwpoison(). There's folio_has_hwpoisoned() to > > > test if _any_ page in the folio is poisoned. But blindly converting > > > PageHWPoison to folio_test_hwpoison() is wrong. > > > > I see a pattern in shmem.c where first the head is tested and for large > > folios, any of pages in the folio is tested for poison flag. Should we > > factor it out as a helper in shmem.c and use it here? > > > > static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, > > ... > > if (folio_test_hwpoison(folio) || > > (folio_test_large(folio) && > > folio_test_has_hwpoisoned(folio))) { > > .. > > Hugh's commit 72887c976a7c9e ("shmem: minor fixes to splice-read > implementation") is on point about this : > > "Perhaps that ugliness can be improved at the mm end later" > > So how about we put some lipstick on this guy now (notice right above it > a similar compound page check for is_page_hwpoison()): > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 1c68d67b832f..6a4a571dbe50 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -883,6 +883,13 @@ static inline bool is_page_hwpoison(struct page *page) > return PageHuge(page) && PageHWPoison(compound_head(page)); > } > > +static inline bool is_folio_hwpoison(struct folio *folio) > +{ > + if (folio_test_hwpoison(folio)) > + return true; > + return folio_test_large(folio) && folio_test_has_hwpoisoned(folio); > +} > + > /* > * For pages that are never mapped to userspace (and aren't PageSlab), > * page_type may be used. Because it is initialised to -1, we invert the > diff --git a/mm/shmem.c b/mm/shmem.c > index ef7ad684f4fb..b7f47f6b75d5 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3013,9 +3013,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, > if (folio) { > folio_unlock(folio); > > - if (folio_test_hwpoison(folio) || > - (folio_test_large(folio) && > - folio_test_has_hwpoisoned(folio))) { > + if (is_folio_hwpoison(folio)) { > error = -EIO; > break; > } With this, this I end up with the following for shmem_file_read_iter(). For some odd reason without the first hunk I see that some non SB_KERNMOUNT end up with a silly inode->i_blkbits. I must be doing something wrong with the shmem_file_read_iter() conversion as I end up with a empty new line at the end, but I can't seem to understand why. Any ideas? diff --git a/mm/shmem.c b/mm/shmem.c index 21a4b8522ac5..39ae17774dc3 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2541,6 +2541,10 @@ static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block inode->i_ino = ino; inode_init_owner(idmap, inode, dir, mode); inode->i_blocks = 0; + if (sb->s_flags & SB_KERNMOUNT) + inode->i_blkbits = PAGE_SHIFT; + else + inode->i_blkbits = sb->s_blocksize_bits; inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); inode->i_generation = get_random_u32(); info = SHMEM_I(inode); @@ -2786,18 +2790,23 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) struct file *file = iocb->ki_filp; struct inode *inode = file_inode(file); struct address_space *mapping = inode->i_mapping; + struct super_block *sb = inode->i_sb; + u64 bsize = i_blocksize(inode); pgoff_t index; unsigned long offset; int error = 0; ssize_t retval = 0; loff_t *ppos = &iocb->ki_pos; + /* + * Although our index is page specific, we can read a blocksize at a + * time as we use a folio per block. + */ index = *ppos >> PAGE_SHIFT; - offset = *ppos & ~PAGE_MASK; + offset = *ppos & (bsize - 1); for (;;) { struct folio *folio = NULL; - struct page *page = NULL; pgoff_t end_index; unsigned long nr, ret; loff_t i_size = i_size_read(inode); @@ -2806,7 +2815,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) if (index > end_index) break; if (index == end_index) { - nr = i_size & ~PAGE_MASK; + nr = i_size & (bsize - 1); if (nr <= offset) break; } @@ -2819,9 +2828,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) } if (folio) { folio_unlock(folio); - - page = folio_file_page(folio, index); - if (PageHWPoison(page)) { + if (is_folio_hwpoison(folio)) { folio_put(folio); error = -EIO; break; @@ -2831,50 +2838,63 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) /* * We must evaluate after, since reads (unlike writes) * are called without i_rwsem protection against truncate + * + * nr represents the number of bytes we can read per folio, + * and this will depend on the blocksize set. */ - nr = PAGE_SIZE; + nr = bsize; + WARN_ON(!(sb->s_flags & SB_KERNMOUNT) && folio && bsize != folio_size(folio)); i_size = i_size_read(inode); end_index = i_size >> PAGE_SHIFT; if (index == end_index) { - nr = i_size & ~PAGE_MASK; + nr = i_size & (bsize - 1); if (nr <= offset) { if (folio) folio_put(folio); break; } } + /* + * On the first folio read this will amount to blocksize - offset. On subsequent + * reads we can read blocksize at time until iov_iter_count(to) == 0. + * + * The offset represents the base we'll use to do the reads per folio, it + * gets incremented by the number of bytes we read per folio and is aligned + * to the blocksize. After a first offset block the offset would be 0 and + * we'd read a block at a time. + */ nr -= offset; if (folio) { /* - * If users can be writing to this page using arbitrary + * If users can be writing to this folio using arbitrary * virtual addresses, take care about potential aliasing - * before reading the page on the kernel side. + * before reading the folio on the kernel side. */ if (mapping_writably_mapped(mapping)) - flush_dcache_page(page); + flush_dcache_folio(folio); /* - * Mark the page accessed if we read the beginning. + * Mark the folio accessed if we read the beginning. */ if (!offset) folio_mark_accessed(folio); /* - * Ok, we have the page, and it's up-to-date, so + * Ok, we have the folio, and it's up-to-date, so * now we can copy it to user space... */ - ret = copy_page_to_iter(page, offset, nr, to); + ret = copy_folio_to_iter(folio, offset, nr, to); folio_put(folio); } else if (user_backed_iter(to)) { /* * Copy to user tends to be so well optimized, but * clear_user() not so much, that it is noticeably - * faster to copy the zero page instead of clearing. + * faster to copy the zero folio instead of clearing. */ - ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to); + ret = copy_folio_to_iter(page_folio(ZERO_PAGE(0)), offset, nr, to); } else { /* - * But submitting the same page twice in a row to + * But submitting the same folio twice in a row to * splice() - or others? - can result in confusion: * so don't attempt that optimization on pipes etc. */ @@ -2883,8 +2903,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) retval += ret; offset += ret; + + /* + * Due to usage of folios per blocksize we know this will actually read + * blocksize at a time after the first block read at offset. + */ index += offset >> PAGE_SHIFT; - offset &= ~PAGE_MASK; + offset &= (bsize - 1); if (!iov_iter_count(to)) break;
diff --git a/mm/shmem.c b/mm/shmem.c index 5bf92d571092..6f117c3cbe89 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3483,7 +3483,7 @@ static const char *shmem_get_link(struct dentry *dentry, folio = filemap_get_folio(inode->i_mapping, 0); if (IS_ERR(folio)) return ERR_PTR(-ECHILD); - if (PageHWPoison(folio_page(folio, 0)) || + if (folio_test_hwpoison(folio) || !folio_test_uptodate(folio)) { folio_put(folio); return ERR_PTR(-ECHILD); @@ -3494,7 +3494,7 @@ static const char *shmem_get_link(struct dentry *dentry, return ERR_PTR(error); if (!folio) return ERR_PTR(-ECHILD); - if (PageHWPoison(folio_page(folio, 0))) { + if (folio_test_hwpoison(folio)) { folio_unlock(folio); folio_put(folio); return ERR_PTR(-ECHILD); @@ -4672,7 +4672,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, return &folio->page; page = folio_file_page(folio, index); - if (PageHWPoison(page)) { + if (folio_test_hwpoison(folio)) { folio_put(folio); return ERR_PTR(-EIO); }
The PageHWPoison() call can be converted over to the respective folio call folio_test_hwpoison(). This introduces no functional changes. Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> --- mm/shmem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)