diff options
| author | Josef Bacik <josef@toxicpanda.com> | 2024-11-15 10:30:29 -0500 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2024-12-11 17:28:41 +0100 |
| commit | 8392bc2ff8c8bf7c4c5e6dfa71ccd893a3c046f6 (patch) | |
| tree | 4d0ad92f307895589ef8e428dc0c4f9a587679d3 /mm/filemap.c | |
| parent | 20bf82a898b65c129af76deb96a1b415d3098a28 (diff) | |
| download | linux-8392bc2ff8c8bf7c4c5e6dfa71ccd893a3c046f6.tar.gz | |
fsnotify: generate pre-content permission event on page fault
FS_PRE_ACCESS will be generated on page fault depending on the faulting
method. This pre-content event is meant to be used by hierarchical storage
managers that want to fill in the file content on first read access.
Export a simple helper that file systems that have their own ->fault()
will use, and have a more complicated helper to be do fancy things in
filemap_fault.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/aa56c50ce81b1fd18d7f5d71dd2dfced5eba9687.1731684329.git.josef@toxicpanda.com
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index e9a0f330d33ee0..6fdd5dc093c0a5 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -47,6 +47,7 @@ #include <linux/splice.h> #include <linux/rcupdate_wait.h> #include <linux/sched/mm.h> +#include <linux/fsnotify.h> #include <asm/pgalloc.h> #include <asm/tlbflush.h> #include "internal.h" @@ -3289,6 +3290,48 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf) } /** + * filemap_fsnotify_fault - maybe emit a pre-content event. + * @vmf: struct vm_fault containing details of the fault. + * + * If we have a pre-content watch on this file we will emit an event for this + * range. If we return anything the fault caller should return immediately, we + * will return VM_FAULT_RETRY if we had to emit an event, which will trigger the + * fault again and then the fault handler will run the second time through. + * + * Return: a bitwise-OR of %VM_FAULT_ codes, 0 if nothing happened. + */ +vm_fault_t filemap_fsnotify_fault(struct vm_fault *vmf) +{ + struct file *fpin = NULL; + int mask = (vmf->flags & FAULT_FLAG_WRITE) ? MAY_WRITE : MAY_ACCESS; + loff_t pos = vmf->pgoff >> PAGE_SHIFT; + size_t count = PAGE_SIZE; + int err; + + /* + * We already did this and now we're retrying with everything locked, + * don't emit the event and continue. + */ + if (vmf->flags & FAULT_FLAG_TRIED) + return 0; + + /* No watches, we're done. */ + if (likely(!FMODE_FSNOTIFY_HSM(vmf->vma->vm_file->f_mode))) + return 0; + + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + if (!fpin) + return VM_FAULT_SIGBUS; + + err = fsnotify_file_area_perm(fpin, mask, &pos, count); + fput(fpin); + if (err) + return VM_FAULT_SIGBUS; + return VM_FAULT_RETRY; +} +EXPORT_SYMBOL_GPL(filemap_fsnotify_fault); + +/** * filemap_fault - read in file data for page fault handling * @vmf: struct vm_fault containing details of the fault * @@ -3392,6 +3435,37 @@ retry_find: */ if (unlikely(!folio_test_uptodate(folio))) { /* + * If this is a precontent file we have can now emit an event to + * try and populate the folio. + */ + if (!(vmf->flags & FAULT_FLAG_TRIED) && + unlikely(FMODE_FSNOTIFY_HSM(file->f_mode))) { + loff_t pos = folio_pos(folio); + size_t count = folio_size(folio); + + /* We're NOWAIT, we have to retry. */ + if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) { + folio_unlock(folio); + goto out_retry; + } + + if (mapping_locked) + filemap_invalidate_unlock_shared(mapping); + mapping_locked = false; + + folio_unlock(folio); + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + if (!fpin) + goto out_retry; + + error = fsnotify_file_area_perm(fpin, MAY_ACCESS, &pos, + count); + if (error) + ret = VM_FAULT_SIGBUS; + goto out_retry; + } + + /* * If the invalidate lock is not held, the folio was in cache * and uptodate and now it is not. Strange but possible since we * didn't hold the page lock all the time. Let's drop |