| Message ID | 5ce248ad6e7b551c6d566fd4580795f7a3495352.1725481503.git.josef@toxicpanda.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fanotify: add pre-content hooks | expand |
On Wed, Sep 4, 2024 at 10:29 PM Josef Bacik <josef@toxicpanda.com> wrote: > > With page faults we can trigger readahead on the file, and then > subsequent faults can find these pages and insert them into the file > without emitting an fanotify event. To avoid this case, disable > readahead if we have pre-content watches on the file. This way we are > guaranteed to get an event for every range we attempt to access on a > pre-content watched file. > > Reviewed-by: Christian Brauner <brauner@kernel.org> > Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Thanks, Amir. > --- > mm/filemap.c | 12 ++++++++++++ > mm/readahead.c | 13 +++++++++++++ > 2 files changed, 25 insertions(+) > > diff --git a/mm/filemap.c b/mm/filemap.c > index ca8c8d889eef..8b1684b62177 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -3122,6 +3122,14 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) > unsigned long vm_flags = vmf->vma->vm_flags; > unsigned int mmap_miss; > > + /* > + * If we have pre-content watches we need to disable readahead to make > + * sure that we don't populate our mapping with 0 filled pages that we > + * never emitted an event for. > + */ > + if (fsnotify_file_has_pre_content_watches(file)) > + return fpin; > + > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > /* Use the readahead code, even if readahead is disabled */ > if ((vm_flags & VM_HUGEPAGE) && HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) { > @@ -3190,6 +3198,10 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, > struct file *fpin = NULL; > unsigned int mmap_miss; > > + /* See comment in do_sync_mmap_readahead. */ > + if (fsnotify_file_has_pre_content_watches(file)) > + return fpin; > + > /* If we don't want any read-ahead, don't bother */ > if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) > return fpin; > diff --git a/mm/readahead.c b/mm/readahead.c > index 817b2a352d78..bc068d9218e3 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -128,6 +128,7 @@ > #include <linux/blk-cgroup.h> > #include <linux/fadvise.h> > #include <linux/sched/mm.h> > +#include <linux/fsnotify.h> > > #include "internal.h" > > @@ -674,6 +675,14 @@ void page_cache_sync_ra(struct readahead_control *ractl, > { > bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM); > > + /* > + * If we have pre-content watches we need to disable readahead to make > + * sure that we don't find 0 filled pages in cache that we never emitted > + * events for. > + */ > + if (ractl->file && fsnotify_file_has_pre_content_watches(ractl->file)) > + return; > + > /* > * Even if readahead is disabled, issue this request as readahead > * as we'll need it to satisfy the requested range. The forced > @@ -704,6 +713,10 @@ void page_cache_async_ra(struct readahead_control *ractl, > if (!ractl->ra->ra_pages) > return; > > + /* See the comment in page_cache_sync_ra. */ > + if (ractl->file && fsnotify_file_has_pre_content_watches(ractl->file)) > + return; > + > /* > * Same bit is used for PG_readahead and PG_reclaim. > */ > -- > 2.43.0 >
diff --git a/mm/filemap.c b/mm/filemap.c index ca8c8d889eef..8b1684b62177 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3122,6 +3122,14 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) unsigned long vm_flags = vmf->vma->vm_flags; unsigned int mmap_miss; + /* + * If we have pre-content watches we need to disable readahead to make + * sure that we don't populate our mapping with 0 filled pages that we + * never emitted an event for. + */ + if (fsnotify_file_has_pre_content_watches(file)) + return fpin; + #ifdef CONFIG_TRANSPARENT_HUGEPAGE /* Use the readahead code, even if readahead is disabled */ if ((vm_flags & VM_HUGEPAGE) && HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) { @@ -3190,6 +3198,10 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, struct file *fpin = NULL; unsigned int mmap_miss; + /* See comment in do_sync_mmap_readahead. */ + if (fsnotify_file_has_pre_content_watches(file)) + return fpin; + /* If we don't want any read-ahead, don't bother */ if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) return fpin; diff --git a/mm/readahead.c b/mm/readahead.c index 817b2a352d78..bc068d9218e3 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -128,6 +128,7 @@ #include <linux/blk-cgroup.h> #include <linux/fadvise.h> #include <linux/sched/mm.h> +#include <linux/fsnotify.h> #include "internal.h" @@ -674,6 +675,14 @@ void page_cache_sync_ra(struct readahead_control *ractl, { bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM); + /* + * If we have pre-content watches we need to disable readahead to make + * sure that we don't find 0 filled pages in cache that we never emitted + * events for. + */ + if (ractl->file && fsnotify_file_has_pre_content_watches(ractl->file)) + return; + /* * Even if readahead is disabled, issue this request as readahead * as we'll need it to satisfy the requested range. The forced @@ -704,6 +713,10 @@ void page_cache_async_ra(struct readahead_control *ractl, if (!ractl->ra->ra_pages) return; + /* See the comment in page_cache_sync_ra. */ + if (ractl->file && fsnotify_file_has_pre_content_watches(ractl->file)) + return; + /* * Same bit is used for PG_readahead and PG_reclaim. */