Changes since last update:

- Mark I/Os as failed when encountering short reads on file-backed
    mounts
 
  - Label GFP_NOIO in the BIO completion when the completion is in
    the process context, and directly call into the decompression
    to avoid deadlocks
 
  - Improve Kconfig descriptions to better highlight the overall
    efforts
 
  - Fix .fadvise() for page cache sharing
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Merge tag 'erofs-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs fixes from Gao Xiang:

 - Mark I/Os as failed when encountering short reads on file-backed
   mounts

 - Label GFP_NOIO in the BIO completion when the completion is in the
   process context, and directly call into the decompression to avoid
   deadlocks

 - Improve Kconfig descriptions to better highlight the overall efforts

 - Fix .fadvise() for page cache sharing

* tag 'erofs-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: fix .fadvise() for page cache sharing
  erofs: update the Kconfig description
  erofs: add GFP_NOIO in the bio completion if needed
  erofs: set fileio bio failed in short read case

fs/erofs/Kconfig

@@ -16,22 +16,36 @@ config EROFS_FS
 	select ZLIB_INFLATE if EROFS_FS_ZIP_DEFLATE
 	select ZSTD_DECOMPRESS if EROFS_FS_ZIP_ZSTD
 	help
-	  EROFS (Enhanced Read-Only File System) is a lightweight read-only
-	  file system with modern designs (e.g. no buffer heads, inline
-	  xattrs/data, chunk-based deduplication, multiple devices, etc.) for
-	  scenarios which need high-performance read-only solutions, e.g.
-	  smartphones with Android OS, LiveCDs and high-density hosts with
-	  numerous containers;
+	  EROFS (Enhanced Read-Only File System) is a modern, lightweight,
+	  secure read-only filesystem for various use cases, such as immutable
+	  system images, container images, application sandboxes, and datasets.
 
-	  It also provides transparent compression and deduplication support to
-	  improve storage density and maintain relatively high compression
-	  ratios, and it implements in-place decompression to temporarily reuse
-	  page cache for compressed data using proper strategies, which is
-	  quite useful for ensuring guaranteed end-to-end runtime decompression
+	  EROFS uses a flexible, hierarchical on-disk design so that features
+	  can be enabled on demand: the core on-disk format is block-aligned in
+	  order to perform optimally on all kinds of devices, including block
+	  and memory-backed devices; the format is easy to parse and has zero
+	  metadata redundancy, unlike generic filesystems, making it ideal for
+	  filesystem auditing and remote access; inline data, random-access
+	  friendly directory data, inline/shared extended attributes and
+	  chunk-based deduplication ensure space efficiency while maintaining
+	  high performance.
+
+	  Optionally, it supports multiple devices to reference external data,
+	  enabling data sharing for container images.
+
+	  It also has advanced encoded on-disk layouts, particularly for data
+	  compression and fine-grained deduplication. It utilizes fixed-size
+	  output compression to improve storage density while keeping relatively
+	  high compression ratios. Furthermore, it implements in-place
+	  decompression to reuse file pages to keep compressed data temporarily
+	  with proper strategies, which ensures guaranteed end-to-end runtime
 	  performance under extreme memory pressure without extra cost.
 
-	  See the documentation at <file:Documentation/filesystems/erofs.rst>
-	  and the web pages at <https://erofs.docs.kernel.org> for more details.
+	  For more details, see the web pages at <https://erofs.docs.kernel.org>
+	  and the documentation at <file:Documentation/filesystems/erofs.rst>.
+
+	  To compile EROFS filesystem support as a module, choose M here. The
+	  module will be called erofs.
 
 	  If unsure, say N.
 
@@ -105,7 +119,8 @@ config EROFS_FS_ZIP
 	depends on EROFS_FS
 	default y
 	help
-	  Enable transparent compression support for EROFS file systems.
+	  Enable EROFS compression layouts so that filesystems containing
+	  compressed files can be parsed by the kernel.
 
 	  If you don't want to enable compression feature, say N.
 

fs/erofs/fileio.c

@@ -25,10 +25,8 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 			container_of(iocb, struct erofs_fileio_rq, iocb);
 	struct folio_iter fi;
 
-	if (ret >= 0 && ret != rq->bio.bi_iter.bi_size) {
-		bio_advance(&rq->bio, ret);
-		zero_fill_bio(&rq->bio);
-	}
+	if (ret >= 0 && ret != rq->bio.bi_iter.bi_size)
+		ret = -EIO;
 	if (!rq->bio.bi_end_io) {
 		bio_for_each_folio_all(fi, &rq->bio) {
 			DBG_BUGON(folio_test_uptodate(fi.folio));

fs/erofs/ishare.c

@@ -200,8 +200,19 @@ struct inode *erofs_real_inode(struct inode *inode, bool *need_iput)
 
 int __init erofs_init_ishare(void)
 {
-	erofs_ishare_mnt = kern_mount(&erofs_anon_fs_type);
-	return PTR_ERR_OR_ZERO(erofs_ishare_mnt);
+	struct vfsmount *mnt;
+	int ret;
+
+	mnt = kern_mount(&erofs_anon_fs_type);
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+	/* generic_fadvise() doesn't work if s_bdi == &noop_backing_dev_info */
+	ret = super_setup_bdi(mnt->mnt_sb);
+	if (ret)
+		kern_unmount(mnt);
+	else
+		erofs_ishare_mnt = mnt;
+	return ret;
 }
 
 void erofs_exit_ishare(void)

fs/erofs/zdata.c

@@ -1445,6 +1445,7 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       int bios)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
+	int gfp_flag;
 
 	/* wake up the caller thread for sync decompression */
 	if (io->sync) {
@@ -1477,7 +1478,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 			sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
 		return;
 	}
+	gfp_flag = memalloc_noio_save();
 	z_erofs_decompressqueue_work(&io->u.work);
+	memalloc_noio_restore(gfp_flag);
 }
 
 static void z_erofs_fill_bio_vec(struct bio_vec *bvec,