| Message ID | 20230621212403.174710-2-mike.kravetz@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] Revert "page cache: fix page_cache_next/prev_miss off by one" | expand |
On 6/21/23 2:24 PM, Mike Kravetz wrote: > Ackerley Tng reported an issue with hugetlbfs fallocate as noted in the > Closes tag. The issue showed up after the conversion of hugetlb page > cache lookup code to use page_cache_next_miss. User visible effects are: > - hugetlbfs fallocate incorrectly returns -EEXIST if pages are presnet > in the file. > - hugetlb pages will not be included in core dumps if they need to be > brought in via GUP. > - userfaultfd UFFDIO_COPY will not notice pages already present in the > cache. It may try to allocate a new page and potentially return > ENOMEM as opposed to EEXIST. > > Revert the use page_cache_next_miss() in hugetlb code. > > IMPORTANT NOTE FOR STABLE BACKPORTS: > This patch will apply cleanly to v6.3. However, due to the change of > filemap_get_folio() return values, it will not function correctly. This > patch must be modified for stable backports. This patch I sent previously can be used for the 6.3 backport: https://lore.kernel.org/lkml/b5bd2b39-7e1e-148f-7462-9565773f6d41@oracle.com/T/#me37b56ca89368dc8dda2a33d39f681337788d13c > > Fixes: d0ce0e47b323 ("mm/hugetlb: convert hugetlb fault paths to use alloc_hugetlb_folio()") > Reported-by: Ackerley Tng <ackerleytng@google.com> > Closes: https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> > --- > fs/hugetlbfs/inode.c | 8 +++----- > mm/hugetlb.c | 11 +++++------ > 2 files changed, 8 insertions(+), 11 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 90361a922cec..7b17ccfa039d 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -821,7 +821,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, > */ > struct folio *folio; > unsigned long addr; > - bool present; > > cond_resched(); > > @@ -842,10 +841,9 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, > mutex_lock(&hugetlb_fault_mutex_table[hash]); > > /* See if already present in mapping to avoid alloc/free */ > - rcu_read_lock(); > - present = page_cache_next_miss(mapping, index, 1) != index; > - rcu_read_unlock(); > - if (present) { > + folio = filemap_get_folio(mapping, index); > + if (!IS_ERR(folio)) { > + folio_put(folio); > mutex_unlock(&hugetlb_fault_mutex_table[hash]); > continue; > } > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index d76574425da3..cb9077b96b43 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5728,13 +5728,12 @@ static bool hugetlbfs_pagecache_present(struct hstate *h, > { > struct address_space *mapping = vma->vm_file->f_mapping; > pgoff_t idx = vma_hugecache_offset(h, vma, address); > - bool present; > - > - rcu_read_lock(); > - present = page_cache_next_miss(mapping, idx, 1) != idx; > - rcu_read_unlock(); > + struct folio *folio; > > - return present; > + folio = filemap_get_folio(mapping, idx); > + if (!IS_ERR(folio)) > + folio_put(folio); > + return folio != NULL; > } > > int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping, Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
On Wed, 21 Jun 2023 15:19:58 -0700 Sidhartha Kumar <sidhartha.kumar@oracle.com> wrote: > > IMPORTANT NOTE FOR STABLE BACKPORTS: > > This patch will apply cleanly to v6.3. However, due to the change of > > filemap_get_folio() return values, it will not function correctly. This > > patch must be modified for stable backports. > > This patch I sent previously can be used for the 6.3 backport: > > https://lore.kernel.org/lkml/b5bd2b39-7e1e-148f-7462-9565773f6d41@oracle.com/T/#me37b56ca89368dc8dda2a33d39f681337788d13c Are we suggesting that this be backported? If so, I'll add the cc:stable. Because -stable maintainers have been asked not to backport MM patches to which we didn't add the cc:stable.
On 06/21/23 15:39, Andrew Morton wrote: > On Wed, 21 Jun 2023 15:19:58 -0700 Sidhartha Kumar <sidhartha.kumar@oracle.com> wrote: > > > > IMPORTANT NOTE FOR STABLE BACKPORTS: > > > This patch will apply cleanly to v6.3. However, due to the change of > > > filemap_get_folio() return values, it will not function correctly. This > > > patch must be modified for stable backports. > > > > This patch I sent previously can be used for the 6.3 backport: > > > > https://lore.kernel.org/lkml/b5bd2b39-7e1e-148f-7462-9565773f6d41@oracle.com/T/#me37b56ca89368dc8dda2a33d39f681337788d13c > > Are we suggesting that this be backported? If so, I'll add the cc:stable. > > Because -stable maintainers have been asked not to backport MM patches to > which we didn't add the cc:stable. Yes, we need to get a fix into 6.3 as well. The 'issue' with a backport is noted in the IMPORTANT NOTE above. My concern is that adding cc:stable will have it automatically picked up and this would make things worse than they are in 6.3. My 'plan' was to not add the cc:stable, but manually create a patch for 6.3 once this goes upstream. Honestly, I am not sure what is the best way to deal with this. I could also try to catch the email about the automatic backport and say 'no, use this new patch instead'.
On Wed, 21 Jun 2023 15:46:57 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote: > On 06/21/23 15:39, Andrew Morton wrote: > > On Wed, 21 Jun 2023 15:19:58 -0700 Sidhartha Kumar <sidhartha.kumar@oracle.com> wrote: > > > > > > IMPORTANT NOTE FOR STABLE BACKPORTS: > > > > This patch will apply cleanly to v6.3. However, due to the change of > > > > filemap_get_folio() return values, it will not function correctly. This > > > > patch must be modified for stable backports. > > > > > > This patch I sent previously can be used for the 6.3 backport: > > > > > > https://lore.kernel.org/lkml/b5bd2b39-7e1e-148f-7462-9565773f6d41@oracle.com/T/#me37b56ca89368dc8dda2a33d39f681337788d13c > > > > Are we suggesting that this be backported? If so, I'll add the cc:stable. > > > > Because -stable maintainers have been asked not to backport MM patches to > > which we didn't add the cc:stable. > > Yes, we need to get a fix into 6.3 as well. > > The 'issue' with a backport is noted in the IMPORTANT NOTE above. > > My concern is that adding cc:stable will have it automatically picked up > and this would make things worse than they are in 6.3. > > My 'plan' was to not add the cc:stable, but manually create a patch for > 6.3 once this goes upstream. Honestly, I am not sure what is the best > way to deal with this. I could also try to catch the email about the > automatic backport and say 'no, use this new patch instead'. OK, how about I leave it without cc:stable, so you can send the 6.3 version at a time of your choosing?
On 06/21/23 15:52, Andrew Morton wrote: > On Wed, 21 Jun 2023 15:46:57 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote: > > > On 06/21/23 15:39, Andrew Morton wrote: > > > On Wed, 21 Jun 2023 15:19:58 -0700 Sidhartha Kumar <sidhartha.kumar@oracle.com> wrote: > > > > > > > > IMPORTANT NOTE FOR STABLE BACKPORTS: > > > > > This patch will apply cleanly to v6.3. However, due to the change of > > > > > filemap_get_folio() return values, it will not function correctly. This > > > > > patch must be modified for stable backports. > > > > > > > > This patch I sent previously can be used for the 6.3 backport: > > > > > > > > https://lore.kernel.org/lkml/b5bd2b39-7e1e-148f-7462-9565773f6d41@oracle.com/T/#me37b56ca89368dc8dda2a33d39f681337788d13c > > > > > > Are we suggesting that this be backported? If so, I'll add the cc:stable. > > > > > > Because -stable maintainers have been asked not to backport MM patches to > > > which we didn't add the cc:stable. > > > > Yes, we need to get a fix into 6.3 as well. > > > > The 'issue' with a backport is noted in the IMPORTANT NOTE above. > > > > My concern is that adding cc:stable will have it automatically picked up > > and this would make things worse than they are in 6.3. > > > > My 'plan' was to not add the cc:stable, but manually create a patch for > > 6.3 once this goes upstream. Honestly, I am not sure what is the best > > way to deal with this. I could also try to catch the email about the > > automatic backport and say 'no, use this new patch instead'. > > OK, how about I leave it without cc:stable, so you can send the 6.3 > version at a time of your choosing? Perfect
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 90361a922cec..7b17ccfa039d 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -821,7 +821,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, */ struct folio *folio; unsigned long addr; - bool present; cond_resched(); @@ -842,10 +841,9 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, mutex_lock(&hugetlb_fault_mutex_table[hash]); /* See if already present in mapping to avoid alloc/free */ - rcu_read_lock(); - present = page_cache_next_miss(mapping, index, 1) != index; - rcu_read_unlock(); - if (present) { + folio = filemap_get_folio(mapping, index); + if (!IS_ERR(folio)) { + folio_put(folio); mutex_unlock(&hugetlb_fault_mutex_table[hash]); continue; } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d76574425da3..cb9077b96b43 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5728,13 +5728,12 @@ static bool hugetlbfs_pagecache_present(struct hstate *h, { struct address_space *mapping = vma->vm_file->f_mapping; pgoff_t idx = vma_hugecache_offset(h, vma, address); - bool present; - - rcu_read_lock(); - present = page_cache_next_miss(mapping, idx, 1) != idx; - rcu_read_unlock(); + struct folio *folio; - return present; + folio = filemap_get_folio(mapping, idx); + if (!IS_ERR(folio)) + folio_put(folio); + return folio != NULL; } int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,
Ackerley Tng reported an issue with hugetlbfs fallocate as noted in the Closes tag. The issue showed up after the conversion of hugetlb page cache lookup code to use page_cache_next_miss. User visible effects are: - hugetlbfs fallocate incorrectly returns -EEXIST if pages are presnet in the file. - hugetlb pages will not be included in core dumps if they need to be brought in via GUP. - userfaultfd UFFDIO_COPY will not notice pages already present in the cache. It may try to allocate a new page and potentially return ENOMEM as opposed to EEXIST. Revert the use page_cache_next_miss() in hugetlb code. IMPORTANT NOTE FOR STABLE BACKPORTS: This patch will apply cleanly to v6.3. However, due to the change of filemap_get_folio() return values, it will not function correctly. This patch must be modified for stable backports. Fixes: d0ce0e47b323 ("mm/hugetlb: convert hugetlb fault paths to use alloc_hugetlb_folio()") Reported-by: Ackerley Tng <ackerleytng@google.com> Closes: https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- fs/hugetlbfs/inode.c | 8 +++----- mm/hugetlb.c | 11 +++++------ 2 files changed, 8 insertions(+), 11 deletions(-)