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Message-ID: <CAJnrk1Y8Fi7ZgY15WDtKZ1kVAsh-kzfNbEOvHKNwCxtA6iWzWA@mail.gmail.com>
Date: Wed, 21 Jan 2026 18:07:12 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: miklos@...redi.hu, bernd@...ernd.com, neal@...pa.dev,
linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 10/31] fuse: implement basic iomap reporting such as
FIEMAP and SEEK_{DATA,HOLE}
On Tue, Oct 28, 2025 at 5:47 PM Darrick J. Wong <djwong@...nel.org> wrote:
>
> From: Darrick J. Wong <djwong@...nel.org>
>
> Implement the basic file mapping reporting functions like FIEMAP, BMAP,
> and SEEK_DATA/HOLE.
>
> Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
> ---
> fs/fuse/fuse_i.h | 8 ++++++
> fs/fuse/dir.c | 1 +
> fs/fuse/file.c | 13 ++++++++++
> fs/fuse/file_iomap.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 4 files changed, 89 insertions(+), 1 deletion(-)
>
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index c7aeb324fe599e..6fe8aa1845b98d 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -1730,6 +1730,11 @@ static inline bool fuse_inode_has_iomap(const struct inode *inode)
>
> return test_bit(FUSE_I_IOMAP, &fi->state);
> }
> +
> +int fuse_iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> + u64 start, u64 length);
> +loff_t fuse_iomap_lseek(struct file *file, loff_t offset, int whence);
> +sector_t fuse_iomap_bmap(struct address_space *mapping, sector_t block);
> #else
> # define fuse_iomap_enabled(...) (false)
> # define fuse_has_iomap(...) (false)
> @@ -1739,6 +1744,9 @@ static inline bool fuse_inode_has_iomap(const struct inode *inode)
> # define fuse_iomap_init_nonreg_inode(...) ((void)0)
> # define fuse_iomap_evict_inode(...) ((void)0)
> # define fuse_inode_has_iomap(...) (false)
> +# define fuse_iomap_fiemap NULL
> +# define fuse_iomap_lseek(...) (-ENOSYS)
> +# define fuse_iomap_bmap(...) (-ENOSYS)
> #endif
>
> #endif /* _FS_FUSE_I_H */
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index 18eb1bb192bb58..bafc386f2f4d3a 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -2296,6 +2296,7 @@ static const struct inode_operations fuse_common_inode_operations = {
> .set_acl = fuse_set_acl,
> .fileattr_get = fuse_fileattr_get,
> .fileattr_set = fuse_fileattr_set,
> + .fiemap = fuse_iomap_fiemap,
> };
>
> static const struct inode_operations fuse_symlink_inode_operations = {
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index bd9c208a46c78d..8a981f41b1dbd0 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2512,6 +2512,12 @@ static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
> struct fuse_bmap_out outarg;
> int err;
>
> + if (fuse_inode_has_iomap(inode)) {
> + sector_t alt_sec = fuse_iomap_bmap(mapping, block);
> + if (alt_sec > 0)
> + return alt_sec;
> + }
> +
> if (!inode->i_sb->s_bdev || fm->fc->no_bmap)
> return 0;
>
> @@ -2547,6 +2553,13 @@ static loff_t fuse_lseek(struct file *file, loff_t offset, int whence)
> struct fuse_lseek_out outarg;
> int err;
>
> + if (fuse_inode_has_iomap(inode)) {
> + loff_t alt_pos = fuse_iomap_lseek(file, offset, whence);
> +
> + if (alt_pos >= 0 || (alt_pos < 0 && alt_pos != -ENOSYS))
I don't think you technically need the "alt_pos < 0" part here since
the "alt_pos >= 0 ||" part already accounts for that
> + return alt_pos;
> + }
> +
> if (fm->fc->no_lseek)
> goto fallback;
>
> diff --git a/fs/fuse/file_iomap.c b/fs/fuse/file_iomap.c
> index 66a7b8faa31ac2..ce64e7c4860ef8 100644
> --- a/fs/fuse/file_iomap.c
> +++ b/fs/fuse/file_iomap.c
> @@ -4,6 +4,7 @@
> * Author: Darrick J. Wong <djwong@...nel.org>
> */
> #include <linux/iomap.h>
> +#include <linux/fiemap.h>
> #include "fuse_i.h"
> #include "fuse_trace.h"
> #include "iomap_i.h"
> @@ -561,7 +562,7 @@ static int fuse_iomap_end(struct inode *inode, loff_t pos, loff_t count,
> return err;
> }
>
> -const struct iomap_ops fuse_iomap_ops = {
> +static const struct iomap_ops fuse_iomap_ops = {
> .iomap_begin = fuse_iomap_begin,
> .iomap_end = fuse_iomap_end,
> };
> @@ -690,3 +691,68 @@ void fuse_iomap_evict_inode(struct inode *inode)
> if (conn->iomap && fuse_inode_is_exclusive(inode))
> clear_bit(FUSE_I_EXCLUSIVE, &fi->state);
> }
> +
> +int fuse_iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> + u64 start, u64 count)
> +{
> + struct fuse_conn *fc = get_fuse_conn(inode);
> + int error;
> +
> + /*
> + * We are called directly from the vfs so we need to check per-inode
> + * support here explicitly.
> + */
> + if (!fuse_inode_has_iomap(inode))
> + return -EOPNOTSUPP;
> +
> + if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR)
I don't see where FIEMAP_FLAG_SYNC and FIEMAP_FLAG_CACHE are supported
either, should these return -EOPNOTSUPP if they're set as well?
> + return -EOPNOTSUPP;
> +
> + if (fuse_is_bad(inode))
> + return -EIO;
> +
> + if (!fuse_allow_current_process(fc))
> + return -EACCES;
> +
> + inode_lock_shared(inode);
> + error = iomap_fiemap(inode, fieinfo, start, count, &fuse_iomap_ops);
> + inode_unlock_shared(inode);
> +
> + return error;
> +}
> +
> +sector_t fuse_iomap_bmap(struct address_space *mapping, sector_t block)
> +{
> + ASSERT(fuse_inode_has_iomap(mapping->host));
> +
> + return iomap_bmap(mapping, block, &fuse_iomap_ops);
> +}
> +
> +loff_t fuse_iomap_lseek(struct file *file, loff_t offset, int whence)
> +{
> + struct inode *inode = file->f_mapping->host;
> + struct fuse_conn *fc = get_fuse_conn(inode);
> +
> + ASSERT(fuse_inode_has_iomap(inode));
> +
> + if (fuse_is_bad(inode))
> + return -EIO;
> +
> + if (!fuse_allow_current_process(fc))
> + return -EACCES;
> +
> + switch (whence) {
> + case SEEK_HOLE:
> + offset = iomap_seek_hole(inode, offset, &fuse_iomap_ops);
> + break;
> + case SEEK_DATA:
> + offset = iomap_seek_data(inode, offset, &fuse_iomap_ops);
> + break;
> + default:
Does it make sense to have the default case just call generic_file_llseek()?
Thanks,
Joanne
> + return -ENOSYS;
> + }
> +
> + if (offset < 0)
> + return offset;
> + return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
> +}
>
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