gfs2_block_map(9)

✨ gfs2_block_map(9) ✨

okay so real talk, this page lives in the Kernel API Manual and it's all about one little function that maps blocks. bestie, let's get into it 🫶

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💅 SYNOPSIS

int gfs2_block_map (struct inode *inode , sector_t lblock ,
                    struct buffer_head *bh_map , int create );

like, that's the whole vibe. one function, four args, and it returns an int. slay ✨

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🎀 ARGUMENTS

• inode — the inode, obviously 💁‍♀️ the star of the show.
• lblock — the logical block number. like, the block number in logical land, not disk land.
• bh_map — the bh that's getting mapped. this is the buffer head doing the actual work.
• create — true if it's ok to alloc blocks to satisfy the request 👀 so basically "can I go shopping for new blocks if I need to".

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🦋 DESCRIPTION

okay so first thing first: the size of the requested mapping is defined in bh_map->b_size. that's where it lives. no cap.

When lblock is not mapped, this function clears buffer_mapped(bh_map) and leaves bh_map->b_size unchanged. so like, it just kind of... unmapped-vibes it. 🫠

But when lblock and successive blocks are mapped — up to the requested size — it sets buffer_mapped(bh_map) and sets bh_map->b_size to indicate the size of the mapping. so now the buffer knows what it's got. iconic behavior honestly 💅

It also sets buffer_boundary if a read of metadata will be required before the next block can be mapped. that's your little heads-up that you gotta go read some metadata first, no biggie.

And it sets buffer_new if new blocks were allocated. that's a "hey, these blocks are fresh out of the oven" signal 🍓

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🔥 RETURN

Returns errno. that's it. that's the value.

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🌈 SEE ALSO

Kernel file ./fs/gfs2/bmap.c — and the whole squad:

• gfs2_unstuffer_folio(9)
• gfs2_unstuff_dinode(9)
• find_metapath(9)
• metaptr1(9)
• metapointer(9)
• lookup_metapath(9)
• fillup_metapath(9)
• gfs2_extent_length(9)
• gfs2_hole_size(9)
• __gfs2_iomap_alloc(9)
• gfs2_alloc_size(9)
• __gfs2_iomap_get(9)
• gfs2_journaled_truncate(9)
• sweep_bh_for_rgrps(9)
• find_nonnull_ptr(9)
• punch_hole(9)
• do_shrink(9)
• do_grow(9)
• gfs2_setattr_size(9)
• gfs2_free_journal_extents(9)
• gfs2_add_jextent(9)
• gfs2_map_journal_extents(9)
• gfs2_write_alloc_required(9)

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okay that's the whole page bestie, go map some blocks 💖

this lil masterpiece comes to you from ./fs/gfs2, dated October 2026, and it's filed under gfs2_block_map(9) — mwah 😘 🎀