erofs: tidy up synchronous decompression

 - Get rid of `sbi->opt.max_sync_decompress_pages` since it's fixed as
   3 all the time;

 - Add Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES in bytes instead of in pages,
   since for non-4K pages, 3-page limitation makes no sense;

 - Move `sync_decompress` to sbi to avoid unexpected remount impact;

 - Fold z_erofs_is_sync_decompress() into its caller;

 - Better description of sysfs entry `sync_decompress`.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
index 76d9808ed581436d2a01e19361c7d01366da9b40..b9243c7f28d718295a3a4d7beee45c9854e7a548 100644 (file)
--- a/Documentation/ABI/testing/sysfs-fs-erofs
+++ b/Documentation/ABI/testing/sysfs-fs-erofs
@@ -10,12 +10,16 @@ Description:        Shows all enabled kernel features.
 What:          /sys/fs/erofs/<disk>/sync_decompress
 Date:          November 2021
 Contact:       "Huang Jianan" <huangjianan@oppo.com>
-Description:   Control strategy of sync decompression:
+Description:   Control strategy of synchronous decompression. Synchronous
+               decompression tries to decompress in the reader thread for
+               synchronous reads and small asynchronous reads (<= 12 KiB):
 
-               - 0 (default, auto): enable for readpage, and enable for
-                 readahead on atomic contexts only.
-               - 1 (force on): enable for readpage and readahead.
-               - 2 (force off): disable for all situations.
+               - 0 (auto, default): apply to synchronous reads only, but will
+                                    switch to 1 (force on) if any decompression
+                                    request is detected in atomic contexts;
+               - 1 (force on): apply to synchronous reads and small
+                               asynchronous reads;
+               - 2 (force off): disable synchronous decompression completely.
 
 What:          /sys/fs/erofs/<disk>/drop_caches
 Date:          November 2024

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index f7f622836198daeda18b5da81a643312282c44e1..87edbb4366d16ca570c1c484da7d64ac714afda8 100644 (file)
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -59,10 +59,6 @@ enum {
 struct erofs_mount_opts {
        /* current strategy of how to use managed cache */
        unsigned char cache_strategy;
-       /* strategy of sync decompression (0 - auto, 1 - force on, 2 - force off) */
-       unsigned int sync_decompress;
-       /* threshold for decompression synchronously */
-       unsigned int max_sync_decompress_pages;
        unsigned int mount_opt;
 };
 
@@ -116,6 +112,7 @@ struct erofs_sb_info {
        /* managed XArray arranged in physical block number */
        struct xarray managed_pslots;
 
+       unsigned int sync_decompress;   /* strategy for sync decompression */
        unsigned int shrinker_run_no;
        u16 available_compr_algs;
 

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index ee37628ec99fb3e7186d45d37906618855010c5c..984afbda1c18c61c88563d85d313fffed6c8000c 100644 (file)
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -375,8 +375,7 @@ static void erofs_default_options(struct erofs_sb_info *sbi)
 {
 #ifdef CONFIG_EROFS_FS_ZIP
        sbi->opt.cache_strategy = EROFS_ZIP_CACHE_READAROUND;
-       sbi->opt.max_sync_decompress_pages = 3;
-       sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_AUTO;
+       sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_AUTO;
 #endif
 #ifdef CONFIG_EROFS_FS_XATTR
        set_opt(&sbi->opt, XATTR_USER);

diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index 1e0658a1d95b9acad0c665d147d572c2cc10d36e..86b22b9f0c191037e45310e994d59336545ec9e2 100644 (file)
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -59,7 +59,7 @@ static struct erofs_attr erofs_attr_##_name = {                       \
 #define ATTR_LIST(name) (&erofs_attr_##name.attr)
 
 #ifdef CONFIG_EROFS_FS_ZIP
-EROFS_ATTR_RW_UI(sync_decompress, erofs_mount_opts);
+EROFS_ATTR_RW_UI(sync_decompress, erofs_sb_info);
 EROFS_ATTR_FUNC(drop_caches, 0200);
 #endif
 #ifdef CONFIG_EROFS_FS_ZIP_ACCEL

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index c62908f1ce478566bff907b44bffc136e48ba034..5860ea6dbc60cd49d4365303f746f1740a3923dc 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -9,6 +9,7 @@
 #include <linux/cpuhotplug.h>
 #include <trace/events/erofs.h>
 
+#define Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES      12288
 #define Z_EROFS_PCLUSTER_MAX_PAGES     (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
 #define Z_EROFS_INLINE_BVECS           2
 
@@ -1095,21 +1096,6 @@ static int z_erofs_scan_folio(struct z_erofs_frontend *f,
        return err;
 }
 
-static bool z_erofs_is_sync_decompress(struct erofs_sb_info *sbi,
-                                      unsigned int readahead_pages)
-{
-       /* auto: enable for read_folio, disable for readahead */
-       if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&
-           !readahead_pages)
-               return true;
-
-       if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&
-           (readahead_pages <= sbi->opt.max_sync_decompress_pages))
-               return true;
-
-       return false;
-}
-
 static bool z_erofs_page_is_invalidated(struct page *page)
 {
        return !page_folio(page)->mapping && !z_erofs_is_shortlived_page(page);
@@ -1484,9 +1470,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 #else
                queue_work(z_erofs_workqueue, &io->u.work);
 #endif
-               /* enable sync decompression for readahead */
-               if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
-                       sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
+               /* See `sync_decompress` in sysfs-fs-erofs for more details */
+               if (sbi->sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
+                       sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
                return;
        }
        z_erofs_decompressqueue_work(&io->u.work);
@@ -1803,16 +1789,21 @@ drain_io:
        z_erofs_decompress_kickoff(q[JQ_SUBMIT], nr_bios);
 }
 
-static int z_erofs_runqueue(struct z_erofs_frontend *f, unsigned int rapages)
+static int z_erofs_runqueue(struct z_erofs_frontend *f, unsigned int rabytes)
 {
        struct z_erofs_decompressqueue io[NR_JOBQUEUES];
        struct erofs_sb_info *sbi = EROFS_I_SB(f->inode);
-       bool force_fg = z_erofs_is_sync_decompress(sbi, rapages);
+       int syncmode = sbi->sync_decompress;
+       bool force_fg;
        int err;
 
+       force_fg = (syncmode == EROFS_SYNC_DECOMPRESS_AUTO && !rabytes) ||
+               (syncmode == EROFS_SYNC_DECOMPRESS_FORCE_ON &&
+                       (rabytes <= Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES));
+
        if (f->head == Z_EROFS_PCLUSTER_TAIL)
                return 0;
-       z_erofs_submit_queue(f, io, &force_fg, !!rapages);
+       z_erofs_submit_queue(f, io, &force_fg, !!rabytes);
 
        /* handle bypass queue (no i/o pclusters) immediately */
        err = z_erofs_decompress_queue(&io[JQ_BYPASS], &f->pagepool);
@@ -1933,7 +1924,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
        z_erofs_pcluster_readmore(&f, rac, false);
        z_erofs_pcluster_end(&f);
 
-       (void)z_erofs_runqueue(&f, nrpages);
+       (void)z_erofs_runqueue(&f, nrpages << PAGE_SHIFT);
        erofs_put_metabuf(&f.map.buf);
        erofs_release_pages(&f.pagepool);
 }