filemap_check_wb_err(9)

✨ filemap_check_wb_err(9) ✨

okay so bestie, this is a page from the Kernel API Manual and it's genuinely one of the shorter ones, so we're gonna get through it together, no stress 💅

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🌸 NAME 🌸

filemap_check_wb_err — has an error occurred since the mark was sampled?

(yes that's literally the whole question it answers, it's giving "did anything go wrong while you weren't looking" energy 👀)

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🦋 SYNOPSIS 🦋

int filemap_check_wb_err (struct address_space *mapping , errseq_t since
);

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🎀 ARGUMENTS 🎀

• mapping — the mapping you wanna check for writeback errors, like the thing you're side-eyeing 🧐
• since — a previously-sampled errseq_t. that's your "I checked at this moment" bookmark, keep it safe

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💖 DESCRIPTION 💖

So here's the whole vibe, bestie: this function grabs the errseq_t value from the mapping, and then it checks whether that value has changed "since" the given value was sampled. lowkey a vibe check but for error sequence numbers ✨

If it has changed — meaning something happened in between — then it reports the latest error that got set. Otherwise? It just returns 0. clean, no drama, nothing to see here 🫶

that's literally it. short queen behavior 👑

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🔥 SEE ALSO 🔥

Kernel file ./include/linux/pagemap.h, plus this absolute iconic lineup of friends (yes there are a lot of them, they run deep, it's a whole friend group 😭):

• filemap_set_wb_err(9)
• filemap_sample_wb_err(9)
• file_sample_sb_err(9)
• mapping_set_error(9)
• mapping_set_large_folios(9)
• mapping_align_index(9)
• mapping_pmd_folio_support(9)
• folio_flush_mapping(9)
• folio_inode(9)
• folio_attach_private(9)
• folio_change_private(9)
• folio_detach_private(9)
• fgf_t(9)
• fgf_set_order(9)
• write_begin_get_folio(9)
• filemap_get_folio(9)
• filemap_lock_folio(9)
• filemap_grab_folio(9)
• find_get_page(9)
• find_lock_page(9)
• find_or_create_page(9)
• grab_cache_page_nowait(9)
• folio_next_index(9)
• folio_next_pos(9)
• folio_file_page(9)
• folio_contains(9)
• page_pgoff(9)
• folio_pos(9)
• linear_page_delta(9)
• linear_page_index(9)
• linear_anon_page_index(9)
• folio_trylock(9)
• folio_lock(9)
• lock_page(9)
• folio_lock_killable(9)
• filemap_range_needs_writeback(9)
• struct readahead_control(9)
• page_cache_sync_readahead(9)
• page_cache_async_readahead(9)
• readahead_folio(9)
• readahead_pos(9)
• readahead_length(9)
• readahead_index(9)
• readahead_count(9)
• readahead_batch_length(9)
• folio_mkwrite_check_truncate(9)
• i_blocks_per_folio(9)

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and that's the whole page, bestie, short and sweet, we ate and left no crumbs 🌈⭐

sign-off time 🎀 — this lil number lives in ./include/linux, its date stamp says October 2026, and it's page filemap_check_wb_err(9) from the Kernel API Manual. mwah 💜