| Message ID | 20190711140012.1671-2-jack@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xfs: Fix races between readahead and hole punching | expand |
On Thu, Jul 11, 2019 at 04:00:10PM +0200, Jan Kara wrote: > Currently handling of MADV_WILLNEED hint calls directly into readahead > code. Handle it by calling vfs_fadvise() instead so that filesystem can > use its ->fadvise() callback to acquire necessary locks or otherwise > prepare for the request. > > Suggested-by: Amir Goldstein <amir73il@gmail.com> > CC: stable@vger.kernel.org # Needed by "xfs: Fix stale data exposure > when readahead races with hole punch" > Signed-off-by: Jan Kara <jack@suse.cz> Looks reasonable to me, though is this race between readahead and truncate severe enough to try to push it as a fix for 5.3 or are you targetting 5.4? --D > --- > mm/madvise.c | 22 ++++++++++++++++------ > 1 file changed, 16 insertions(+), 6 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 628022e674a7..ae56d0ef337d 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -14,6 +14,7 @@ > #include <linux/userfaultfd_k.h> > #include <linux/hugetlb.h> > #include <linux/falloc.h> > +#include <linux/fadvise.h> > #include <linux/sched.h> > #include <linux/ksm.h> > #include <linux/fs.h> > @@ -275,6 +276,7 @@ static long madvise_willneed(struct vm_area_struct *vma, > unsigned long start, unsigned long end) > { > struct file *file = vma->vm_file; > + loff_t offset; > > *prev = vma; > #ifdef CONFIG_SWAP > @@ -298,12 +300,20 @@ static long madvise_willneed(struct vm_area_struct *vma, > return 0; > } > > - start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; > - if (end > vma->vm_end) > - end = vma->vm_end; > - end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; > - > - force_page_cache_readahead(file->f_mapping, file, start, end - start); > + /* > + * Filesystem's fadvise may need to take various locks. We need to > + * explicitly grab a reference because the vma (and hence the > + * vma's reference to the file) can go away as soon as we drop > + * mmap_sem. > + */ > + *prev = NULL; /* tell sys_madvise we drop mmap_sem */ > + get_file(file); > + up_read(¤t->mm->mmap_sem); > + offset = (loff_t)(start - vma->vm_start) > + + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); > + vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED); > + fput(file); > + down_read(¤t->mm->mmap_sem); > return 0; > } > > -- > 2.16.4 >
On 11/07/2019 17:00, Jan Kara wrote: > Currently handling of MADV_WILLNEED hint calls directly into readahead > code. Handle it by calling vfs_fadvise() instead so that filesystem can > use its ->fadvise() callback to acquire necessary locks or otherwise > prepare for the request. > > Suggested-by: Amir Goldstein <amir73il@gmail.com> > CC: stable@vger.kernel.org # Needed by "xfs: Fix stale data exposure > when readahead races with hole punch" > Signed-off-by: Jan Kara <jack@suse.cz> I had a similar patch for my needs. But did not drop the mmap_sem when calling into the FS. This one is much better. Reviewed-by: Boaz Harrosh <boazh@netapp.com> I tested this patch, Works perfect for my needs. Thank you for this patch Boaz > --- > mm/madvise.c | 22 ++++++++++++++++------ > 1 file changed, 16 insertions(+), 6 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 628022e674a7..ae56d0ef337d 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -14,6 +14,7 @@ > #include <linux/userfaultfd_k.h> > #include <linux/hugetlb.h> > #include <linux/falloc.h> > +#include <linux/fadvise.h> > #include <linux/sched.h> > #include <linux/ksm.h> > #include <linux/fs.h> > @@ -275,6 +276,7 @@ static long madvise_willneed(struct vm_area_struct *vma, > unsigned long start, unsigned long end) > { > struct file *file = vma->vm_file; > + loff_t offset; > > *prev = vma; > #ifdef CONFIG_SWAP > @@ -298,12 +300,20 @@ static long madvise_willneed(struct vm_area_struct *vma, > return 0; > } > > - start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; > - if (end > vma->vm_end) > - end = vma->vm_end; > - end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; > - > - force_page_cache_readahead(file->f_mapping, file, start, end - start); > + /* > + * Filesystem's fadvise may need to take various locks. We need to > + * explicitly grab a reference because the vma (and hence the > + * vma's reference to the file) can go away as soon as we drop > + * mmap_sem. > + */ > + *prev = NULL; /* tell sys_madvise we drop mmap_sem */ > + get_file(file); > + up_read(¤t->mm->mmap_sem); > + offset = (loff_t)(start - vma->vm_start) > + + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); > + vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED); > + fput(file); > + down_read(¤t->mm->mmap_sem); > return 0; > } > >
diff --git a/mm/madvise.c b/mm/madvise.c index 628022e674a7..ae56d0ef337d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -14,6 +14,7 @@ #include <linux/userfaultfd_k.h> #include <linux/hugetlb.h> #include <linux/falloc.h> +#include <linux/fadvise.h> #include <linux/sched.h> #include <linux/ksm.h> #include <linux/fs.h> @@ -275,6 +276,7 @@ static long madvise_willneed(struct vm_area_struct *vma, unsigned long start, unsigned long end) { struct file *file = vma->vm_file; + loff_t offset; *prev = vma; #ifdef CONFIG_SWAP @@ -298,12 +300,20 @@ static long madvise_willneed(struct vm_area_struct *vma, return 0; } - start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; - if (end > vma->vm_end) - end = vma->vm_end; - end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; - - force_page_cache_readahead(file->f_mapping, file, start, end - start); + /* + * Filesystem's fadvise may need to take various locks. We need to + * explicitly grab a reference because the vma (and hence the + * vma's reference to the file) can go away as soon as we drop + * mmap_sem. + */ + *prev = NULL; /* tell sys_madvise we drop mmap_sem */ + get_file(file); + up_read(¤t->mm->mmap_sem); + offset = (loff_t)(start - vma->vm_start) + + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); + vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED); + fput(file); + down_read(¤t->mm->mmap_sem); return 0; }
Currently handling of MADV_WILLNEED hint calls directly into readahead code. Handle it by calling vfs_fadvise() instead so that filesystem can use its ->fadvise() callback to acquire necessary locks or otherwise prepare for the request. Suggested-by: Amir Goldstein <amir73il@gmail.com> CC: stable@vger.kernel.org # Needed by "xfs: Fix stale data exposure when readahead races with hole punch" Signed-off-by: Jan Kara <jack@suse.cz> --- mm/madvise.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)